升级netty版本为4.1.68.Final

2022-09-18 22:05:22 +08:00
parent 279530ade2
commit 7ea1a2b146
44 changed files with 2710 additions and 448 deletions
@@ -112,7 +112,7 @@ abstract public class AdminAction extends Action {
    }

    protected void sendApiMessage(Response response, String fromUser, String clientId, String topic, byte[] message, ApiCallback callback, boolean noAdmin) {
-        ServerAPIHelper.sendRequest(fromUser, clientId, topic, message, new ServerAPIHelper.Callback() {
+        ServerAPIHelper.sendRequest(fromUser, clientId, topic, message, callback == null ? null : new ServerAPIHelper.Callback() {
            @Override
            public void onSuccess(byte[] result) {
                if(callback != null) {
@@ -81,18 +81,6 @@ public class Request {

 		// request URI parameters
 		this.putParams(new QueryStringDecoder(uri));
-		if(nettyRequest.method() != HttpMethod.GET){
-			HttpPostRequestDecoder decoder = null;
-			try {
-				decoder = new HttpPostRequestDecoder(HTTP_DATA_FACTORY, nettyRequest);
-				this.putParams(decoder);
-			} finally {
-				if(null != decoder){
-					decoder.destroy();
-					decoder = null;
-				}
-			}
-		}

 		// IP
 		this.putIp(ctx);
@@ -72,7 +72,7 @@ public class InterceptConnectMessage extends InterceptAbstractMessage {
    }

    public byte[] getPassword() {
-        return msg.payload().password();
+        return msg.payload().passwordInBytes();
    }

    public String getWillTopic() {
@@ -308,7 +308,7 @@ public class ProtocolProcessor {
            }
            byte[] pwd = null;
            if (msg.variableHeader().hasPassword()) {
-                pwd = msg.payload().password();
+                pwd = msg.payload().passwordInBytes();

                MemorySessionStore.Session session = m_sessionsStore.getSession(clientId);
                if (session == null) {
@@ -164,7 +164,7 @@ public class Qos1PublishHandler extends QosPublishHandler {
                        } else {
                            MemorySessionStore.Session session = m_sessionStore.getSession(clientID);
                            if (session != null && session.getUsername().equals(fromUser)) {
-                                if (data.length > 7*1024 && session.getMqttVersion().protocolLevel() >= MqttVersion.Wildfire_1.protocolLevel()) {
+                                if (data.length > 7*1024 && session.getMqttVersion().protocolLevel() >= MqttVersion.MQTT_5.protocolLevel()) {
                                    ByteArrayOutputStream out = new ByteArrayOutputStream();
                                    GZIPOutputStream gzip = null;
                                    try {
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -16,13 +16,30 @@

 package io.netty.handler.codec.mqtt;

+import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.DecoderException;
+import io.netty.util.Attribute;
+import io.netty.util.AttributeKey;

 final class MqttCodecUtil {

    private static final char[] TOPIC_WILDCARDS = {'#', '+'};
-    private static final int MIN_CLIENT_ID_LENGTH = 1;
-    private static final int MAX_CLIENT_ID_LENGTH = 23;
+
+    static final AttributeKey<MqttVersion> MQTT_VERSION_KEY = AttributeKey.valueOf("NETTY_CODEC_MQTT_VERSION");
+
+    static MqttVersion getMqttVersion(ChannelHandlerContext ctx) {
+        Attribute<MqttVersion> attr = ctx.channel().attr(MQTT_VERSION_KEY);
+        MqttVersion version = attr.get();
+        if (version == null) {
+            return MqttVersion.MQTT_3_1_1;
+        }
+        return version;
+    }
+
+    static void setMqttVersion(ChannelHandlerContext ctx, MqttVersion version) {
+        Attribute<MqttVersion> attr = ctx.channel().attr(MQTT_VERSION_KEY);
+        attr.set(version);
+    }

    static boolean isValidPublishTopicName(String topicName) {
        // publish topic name must not contain any wildcard
@@ -38,20 +55,20 @@ final class MqttCodecUtil {
        return messageId != 0;
    }

-    static boolean isValidClientId(MqttVersion mqttVersion, String clientId) {
+    static boolean isValidClientId(MqttVersion mqttVersion, int maxClientIdLength, String clientId) {
        if (mqttVersion == MqttVersion.MQTT_3_1) {
-            return clientId != null && clientId.length() >= MIN_CLIENT_ID_LENGTH &&
-                clientId.length() <= MAX_CLIENT_ID_LENGTH;
+            return clientId != null && clientId.length() >= MqttConstant.MIN_CLIENT_ID_LENGTH &&
+                clientId.length() <= maxClientIdLength;
        }
        if (mqttVersion.protocolLevel() >= MqttVersion.MQTT_3_1_1.protocolLevel()) {
-            // In 3.1.3.1 Client Identifier of MQTT 3.1.1 specification, The Server MAY allow ClientId’s
+            // In 3.1.3.1 Client Identifier of MQTT 3.1.1 and 5.0 specifications, The Server MAY allow ClientId’s
            // that contain more than 23 encoded bytes. And, The Server MAY allow zero-length ClientId.
            return clientId != null;
        }
        throw new IllegalArgumentException(mqttVersion + " is unknown mqtt version");
    }

-    static MqttFixedHeader validateFixedHeader(MqttFixedHeader mqttFixedHeader) {
+    static MqttFixedHeader validateFixedHeader(ChannelHandlerContext ctx, MqttFixedHeader mqttFixedHeader) {
        switch (mqttFixedHeader.messageType()) {
            case PUBREL:
            case SUBSCRIBE:
@@ -59,6 +76,12 @@ final class MqttCodecUtil {
                if (mqttFixedHeader.qosLevel() != MqttQoS.AT_LEAST_ONCE) {
                    throw new DecoderException(mqttFixedHeader.messageType().name() + " message must have QoS 1");
                }
+                return mqttFixedHeader;
+            case AUTH:
+                if (MqttCodecUtil.getMqttVersion(ctx) != MqttVersion.MQTT_5) {
+                    throw new DecoderException("AUTH message requires at least MQTT 5");
+                }
+                return mqttFixedHeader;
            default:
                return mqttFixedHeader;
        }
@@ -75,7 +98,7 @@ final class MqttCodecUtil {
            case UNSUBACK:
            case PINGREQ:
            case PINGRESP:
-            //case DISCONNECT:
+            case DISCONNECT:
                if (mqttFixedHeader.isDup() ||
                        mqttFixedHeader.qosLevel() != MqttQoS.AT_MOST_ONCE ||
                        mqttFixedHeader.isRetain()) {
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,7 +17,7 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#connack">MQTTV3.1/connack</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#connack">MQTTV3.1/connack</a>
 */
 public final class MqttConnAckMessage extends MqttMessage {

@@ -28,7 +28,7 @@ public final class MqttConnAckMessage extends MqttMessage {
    public MqttConnAckMessage(MqttFixedHeader mqttFixedHeader, MqttConnAckVariableHeader variableHeader, MqttConnectAckPayload payload) {
        super(mqttFixedHeader, variableHeader, payload);
    }
-
+    
    @Override
    public MqttConnAckVariableHeader variableHeader() {
        return (MqttConnAckVariableHeader) super.variableHeader();
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -27,9 +27,17 @@ public final class MqttConnAckVariableHeader {

    private final boolean sessionPresent;

+    private final MqttProperties properties;
+
    public MqttConnAckVariableHeader(MqttConnectReturnCode connectReturnCode, boolean sessionPresent) {
+        this(connectReturnCode, sessionPresent, MqttProperties.NO_PROPERTIES);
+    }
+
+    public MqttConnAckVariableHeader(MqttConnectReturnCode connectReturnCode, boolean sessionPresent,
+                                     MqttProperties properties) {
        this.connectReturnCode = connectReturnCode;
        this.sessionPresent = sessionPresent;
+        this.properties = MqttProperties.withEmptyDefaults(properties);
    }

    public MqttConnectReturnCode connectReturnCode() {
@@ -40,6 +48,10 @@ public final class MqttConnAckVariableHeader {
        return sessionPresent;
    }

+    public MqttProperties properties() {
+        return properties;
+    }
+
    @Override
    public String toString() {
        return new StringBuilder(StringUtil.simpleClassName(this))
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,7 +17,7 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#connect">MQTTV3.1/connect</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#connect">MQTTV3.1/connect</a>
 */
 public final class MqttConnectMessage extends MqttMessage {

@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -16,6 +16,9 @@

 package io.netty.handler.codec.mqtt;

+import java.util.Arrays;
+
+import io.netty.util.CharsetUtil;
 import io.netty.util.internal.StringUtil;

 /**
@@ -24,18 +27,55 @@ import io.netty.util.internal.StringUtil;
 public final class MqttConnectPayload {

    private final String clientIdentifier;
+    private final MqttProperties willProperties;
    private final String willTopic;
-    private final String willMessage;
+    private final byte[] willMessage;
    private final String userName;
    private final byte[] password;

+    /**
+     * @deprecated use {@link MqttConnectPayload#MqttConnectPayload(String,
+     * MqttProperties, String, byte[], String, byte[])} instead
+     */
+    @Deprecated
    public MqttConnectPayload(
            String clientIdentifier,
            String willTopic,
            String willMessage,
            String userName,
+            String password) {
+        this(
+          clientIdentifier,
+          MqttProperties.NO_PROPERTIES,
+          willTopic,
+          willMessage.getBytes(CharsetUtil.UTF_8),
+          userName,
+          password.getBytes(CharsetUtil.UTF_8));
+    }
+
+    public MqttConnectPayload(
+            String clientIdentifier,
+            String willTopic,
+            byte[] willMessage,
+            String userName,
+            byte[] password) {
+        this(clientIdentifier,
+                MqttProperties.NO_PROPERTIES,
+                willTopic,
+                willMessage,
+                userName,
+                password);
+    }
+
+    public MqttConnectPayload(
+            String clientIdentifier,
+            MqttProperties willProperties,
+            String willTopic,
+            byte[] willMessage,
+            String userName,
            byte[] password) {
        this.clientIdentifier = clientIdentifier;
+        this.willProperties = MqttProperties.withEmptyDefaults(willProperties);
        this.willTopic = willTopic;
        this.willMessage = willMessage;
        this.userName = userName;
@@ -46,11 +86,23 @@ public final class MqttConnectPayload {
        return clientIdentifier;
    }

+    public MqttProperties willProperties() {
+        return willProperties;
+    }
+
    public String willTopic() {
        return willTopic;
    }

+    /**
+     * @deprecated use {@link MqttConnectPayload#willMessageInBytes()} instead
+     */
+    @Deprecated
    public String willMessage() {
+        return willMessage == null ? null : new String(willMessage, CharsetUtil.UTF_8);
+    }
+
+    public byte[] willMessageInBytes() {
        return willMessage;
    }

@@ -58,7 +110,15 @@ public final class MqttConnectPayload {
        return userName;
    }

-    public byte[] password() {
+    /**
+     * @deprecated use {@link MqttConnectPayload#passwordInBytes()} instead
+     */
+    @Deprecated
+    public String password() {
+        return password == null ? null : new String(password, CharsetUtil.UTF_8);
+    }
+
+    public byte[] passwordInBytes() {
        return password;
    }

@@ -68,9 +128,9 @@ public final class MqttConnectPayload {
            .append('[')
            .append("clientIdentifier=").append(clientIdentifier)
            .append(", willTopic=").append(willTopic)
-            .append(", willMessage=").append(willMessage)
+            .append(", willMessage=").append(Arrays.toString(willMessage))
            .append(", userName=").append(userName)
-            .append(", password=").append(password)
+            .append(", password=").append(Arrays.toString(password))
            .append(']')
            .toString();
    }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -16,31 +16,52 @@

 package io.netty.handler.codec.mqtt;

-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
-
 /**
 * Return Code of {@link MqttConnAckMessage}
 */
 public enum MqttConnectReturnCode {
    CONNECTION_ACCEPTED((byte) 0x00),
+    //MQTT 3 codes
    CONNECTION_REFUSED_UNACCEPTABLE_PROTOCOL_VERSION((byte) 0X01),
    CONNECTION_REFUSED_IDENTIFIER_REJECTED((byte) 0x02),
    CONNECTION_REFUSED_SERVER_UNAVAILABLE((byte) 0x03),
    CONNECTION_REFUSED_BAD_USER_NAME_OR_PASSWORD((byte) 0x04),
    CONNECTION_REFUSED_NOT_AUTHORIZED((byte) 0x05),
    CONNECTION_REFUSED_UNEXPECT_NODE((byte) 0X06),
-    CONNECTION_REFUSED_SESSION_NOT_EXIST((byte) 0x07);
+    CONNECTION_REFUSED_SESSION_NOT_EXIST((byte) 0x07),
+    //MQTT 5 codes
+    CONNECTION_REFUSED_UNSPECIFIED_ERROR((byte) 0x80),
+    CONNECTION_REFUSED_MALFORMED_PACKET((byte) 0x81),
+    CONNECTION_REFUSED_PROTOCOL_ERROR((byte) 0x82),
+    CONNECTION_REFUSED_IMPLEMENTATION_SPECIFIC((byte) 0x83),
+    CONNECTION_REFUSED_UNSUPPORTED_PROTOCOL_VERSION((byte) 0x84),
+    CONNECTION_REFUSED_CLIENT_IDENTIFIER_NOT_VALID((byte) 0x85),
+    CONNECTION_REFUSED_BAD_USERNAME_OR_PASSWORD((byte) 0x86),
+    CONNECTION_REFUSED_NOT_AUTHORIZED_5((byte) 0x87),
+    CONNECTION_REFUSED_SERVER_UNAVAILABLE_5((byte) 0x88),
+    CONNECTION_REFUSED_SERVER_BUSY((byte) 0x89),
+    CONNECTION_REFUSED_BANNED((byte) 0x8A),
+    CONNECTION_REFUSED_BAD_AUTHENTICATION_METHOD((byte) 0x8C),
+    CONNECTION_REFUSED_TOPIC_NAME_INVALID((byte) 0x90),
+    CONNECTION_REFUSED_PACKET_TOO_LARGE((byte) 0x95),
+    CONNECTION_REFUSED_QUOTA_EXCEEDED((byte) 0x97),
+    CONNECTION_REFUSED_PAYLOAD_FORMAT_INVALID((byte) 0x99),
+    CONNECTION_REFUSED_RETAIN_NOT_SUPPORTED((byte) 0x9A),
+    CONNECTION_REFUSED_QOS_NOT_SUPPORTED((byte) 0x9B),
+    CONNECTION_REFUSED_USE_ANOTHER_SERVER((byte) 0x9C),
+    CONNECTION_REFUSED_SERVER_MOVED((byte) 0x9D),
+    CONNECTION_REFUSED_CONNECTION_RATE_EXCEEDED((byte) 0x9F);

-    private static final Map<Byte, MqttConnectReturnCode> VALUE_TO_CODE_MAP;
+    private static final MqttConnectReturnCode[] VALUES;

    static {
-        final Map<Byte, MqttConnectReturnCode> valueMap = new HashMap<Byte, MqttConnectReturnCode>();
-        for (MqttConnectReturnCode code: values()) {
-            valueMap.put(code.byteValue, code);
+        MqttConnectReturnCode[] values = values();
+        VALUES = new MqttConnectReturnCode[160];
+        for (MqttConnectReturnCode code : values) {
+            final int unsignedByte = code.byteValue & 0xFF;
+            // Suppress a warning about out of bounds access since the enum contains only correct values
+            VALUES[unsignedByte] = code;    // lgtm [java/index-out-of-bounds]
        }
-        VALUE_TO_CODE_MAP = Collections.unmodifiableMap(valueMap);
    }

    private final byte byteValue;
@@ -54,9 +75,16 @@ public enum MqttConnectReturnCode {
    }

    public static MqttConnectReturnCode valueOf(byte b) {
-        if (VALUE_TO_CODE_MAP.containsKey(b)) {
-            return VALUE_TO_CODE_MAP.get(b);
+        final int unsignedByte = b & 0xFF;
+        MqttConnectReturnCode mqttConnectReturnCode = null;
+        try {
+            mqttConnectReturnCode = VALUES[unsignedByte];
+        } catch (ArrayIndexOutOfBoundsException ignored) {
+            // no op
        }
-        throw new IllegalArgumentException("unknown connect return code: " + (b & 0xFF));
+        if (mqttConnectReturnCode == null) {
+            throw new IllegalArgumentException("unknown connect return code: " + unsignedByte);
+        }
+        return mqttConnectReturnCode;
    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -32,6 +32,7 @@ public final class MqttConnectVariableHeader {
    private final boolean isWillFlag;
    private final boolean isCleanSession;
    private final int keepAliveTimeSeconds;
+    private final MqttProperties properties;

    public MqttConnectVariableHeader(
            String name,
@@ -43,6 +44,29 @@ public final class MqttConnectVariableHeader {
            boolean isWillFlag,
            boolean isCleanSession,
            int keepAliveTimeSeconds) {
+        this(name,
+                version,
+                hasUserName,
+                hasPassword,
+                isWillRetain,
+                willQos,
+                isWillFlag,
+                isCleanSession,
+                keepAliveTimeSeconds,
+                MqttProperties.NO_PROPERTIES);
+    }
+
+    public MqttConnectVariableHeader(
+            String name,
+            int version,
+            boolean hasUserName,
+            boolean hasPassword,
+            boolean isWillRetain,
+            int willQos,
+            boolean isWillFlag,
+            boolean isCleanSession,
+            int keepAliveTimeSeconds,
+            MqttProperties properties) {
        this.name = name;
        this.version = version;
        this.hasUserName = hasUserName;
@@ -52,6 +76,7 @@ public final class MqttConnectVariableHeader {
        this.isWillFlag = isWillFlag;
        this.isCleanSession = isCleanSession;
        this.keepAliveTimeSeconds = keepAliveTimeSeconds;
+        this.properties = MqttProperties.withEmptyDefaults(properties);
    }

    public String name() {
@@ -90,6 +115,10 @@ public final class MqttConnectVariableHeader {
        return keepAliveTimeSeconds;
    }

+    public MqttProperties properties() {
+        return properties;
+    }
+
    @Override
    public String toString() {
        return new StringBuilder(StringUtil.simpleClassName(this))
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2021 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.mqtt;
+
+public final class MqttConstant {
+
+    private MqttConstant() {
+    }
+
+    /**
+     * Default max bytes in message
+     */
+    public static final int DEFAULT_MAX_BYTES_IN_MESSAGE = 262144; //256KB
+
+    /**
+     * min client id length
+     */
+    public static final int MIN_CLIENT_ID_LENGTH = 1;
+
+    /**
+     * Default max client id length,In the mqtt3.1 protocol,
+     * the default maximum Client Identifier length is 23
+     */
+    public static final int DEFAULT_MAX_CLIENT_ID_LENGTH = 23;
+
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -20,26 +20,22 @@ import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.ReplayingDecoder;
-import io.netty.handler.codec.mqtt.MqttDecoder.DecoderState;
+import io.netty.handler.codec.TooLongFrameException;
 import io.netty.util.CharsetUtil;
+import io.netty.util.internal.ObjectUtil;

 import java.util.ArrayList;
 import java.util.List;

-import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidClientId;
-import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidMessageId;
-import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidPublishTopicName;
-import static io.netty.handler.codec.mqtt.MqttCodecUtil.resetUnusedFields;
-import static io.netty.handler.codec.mqtt.MqttCodecUtil.validateFixedHeader;
-
 /**
 * Decodes Mqtt messages from bytes, following
- * <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html">
- *     the MQTT protocol specification v3.1</a>
+ * the MQTT protocol specification
+ * <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html">v3.1</a>
+ * or
+ * <a href="https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html">v5.0</a>, depending on the
+ * version specified in the CONNECT message that first goes through the channel.
 */
-public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
-
-    private static final int DEFAULT_MAX_BYTES_IN_MESSAGE = 262144; //256K
+public final class MqttDecoder extends ReplayingDecoder<MqttDecoder.DecoderState> {

    /**
     * States of the decoder.
@@ -58,31 +54,42 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
    private int bytesRemainingInVariablePart;

    private final int maxBytesInMessage;
+    private final int maxClientIdLength;

    public MqttDecoder() {
-      this(DEFAULT_MAX_BYTES_IN_MESSAGE);
+      this(MqttConstant.DEFAULT_MAX_BYTES_IN_MESSAGE, MqttConstant.DEFAULT_MAX_CLIENT_ID_LENGTH);
    }

    public MqttDecoder(int maxBytesInMessage) {
+        this(maxBytesInMessage, MqttConstant.DEFAULT_MAX_CLIENT_ID_LENGTH);
+    }
+
+    public MqttDecoder(int maxBytesInMessage, int maxClientIdLength) {
        super(DecoderState.READ_FIXED_HEADER);
-        this.maxBytesInMessage = maxBytesInMessage;
+        this.maxBytesInMessage = ObjectUtil.checkPositive(maxBytesInMessage, "maxBytesInMessage");
+        this.maxClientIdLength = ObjectUtil.checkPositive(maxClientIdLength, "maxClientIdLength");
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out) throws Exception {
        switch (state()) {
-            case READ_FIXED_HEADER:
-                mqttFixedHeader = decodeFixedHeader(buffer);
+            case READ_FIXED_HEADER: try {
+                mqttFixedHeader = decodeFixedHeader(ctx, buffer);
                bytesRemainingInVariablePart = mqttFixedHeader.remainingLength();
                checkpoint(DecoderState.READ_VARIABLE_HEADER);
                // fall through
+            } catch (Exception cause) {
+                out.add(invalidMessage(cause));
+                return;
+            }

            case READ_VARIABLE_HEADER:  try {
-                if (bytesRemainingInVariablePart > maxBytesInMessage) {
-                    throw new DecoderException("too large message: " + bytesRemainingInVariablePart + " bytes");
-                }
-                final Result<?> decodedVariableHeader = decodeVariableHeader(buffer, mqttFixedHeader);
+                final Result<?> decodedVariableHeader = decodeVariableHeader(ctx, buffer, mqttFixedHeader);
                variableHeader = decodedVariableHeader.value;
+                if (bytesRemainingInVariablePart > maxBytesInMessage) {
+                    buffer.skipBytes(actualReadableBytes());
+                    throw new TooLongFrameException("too large message: " + bytesRemainingInVariablePart + " bytes");
+                }
                bytesRemainingInVariablePart -= decodedVariableHeader.numberOfBytesConsumed;
                checkpoint(DecoderState.READ_PAYLOAD);
                // fall through
@@ -94,9 +101,11 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
            case READ_PAYLOAD: try {
                final Result<?> decodedPayload =
                        decodePayload(
+                                ctx,
                                buffer,
                                mqttFixedHeader.messageType(),
                                bytesRemainingInVariablePart,
+                                maxClientIdLength,
                                variableHeader);
                bytesRemainingInVariablePart -= decodedPayload.numberOfBytesConsumed;
                if (bytesRemainingInVariablePart != 0) {
@@ -129,16 +138,20 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {

    private MqttMessage invalidMessage(Throwable cause) {
      checkpoint(DecoderState.BAD_MESSAGE);
-      return MqttMessageFactory.newInvalidMessage(cause);
+      return MqttMessageFactory.newInvalidMessage(mqttFixedHeader, variableHeader, cause);
    }

    /**
-     * Decodes the fixed header. It's one byte for the flags and then variable bytes for the remaining length.
+     * Decodes the fixed header. It's one byte for the flags and then variable
+     * bytes for the remaining length.
+     *
+     * @see
+     * https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/errata01/os/mqtt-v3.1.1-errata01-os-complete.html#_Toc442180841
     *
     * @param buffer the buffer to decode from
     * @return the fixed header
     */
-    private static MqttFixedHeader decodeFixedHeader(ByteBuf buffer) {
+    private static MqttFixedHeader decodeFixedHeader(ChannelHandlerContext ctx, ByteBuf buffer) {
        short b1 = buffer.readUnsignedByte();

        MqttMessageType messageType = MqttMessageType.valueOf(b1 >> 4);
@@ -146,6 +159,59 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        int qosLevel = (b1 & 0x06) >> 1;
        boolean retain = (b1 & 0x01) != 0;

+        switch (messageType) {
+            case PUBLISH:
+                if (qosLevel == 3) {
+                    throw new DecoderException("Illegal QOS Level in fixed header of PUBLISH message ("
+                            + qosLevel + ')');
+                }
+                break;
+
+            case PUBREL:
+            case SUBSCRIBE:
+            case UNSUBSCRIBE:
+                if (dupFlag) {
+                    throw new DecoderException("Illegal BIT 3 in fixed header of " + messageType
+                            + " message, must be 0, found 1");
+                }
+                if (qosLevel != 1) {
+                    throw new DecoderException("Illegal QOS Level in fixed header of " + messageType
+                            + " message, must be 1, found " + qosLevel);
+                }
+                if (retain) {
+                    throw new DecoderException("Illegal BIT 0 in fixed header of " + messageType
+                            + " message, must be 0, found 1");
+                }
+                break;
+
+            case AUTH:
+            case CONNACK:
+            case CONNECT:
+            case DISCONNECT:
+            case PINGREQ:
+            case PINGRESP:
+            case PUBACK:
+            case PUBCOMP:
+            case PUBREC:
+            case SUBACK:
+            case UNSUBACK:
+                if (dupFlag) {
+                    throw new DecoderException("Illegal BIT 3 in fixed header of " + messageType
+                            + " message, must be 0, found 1");
+                }
+                if (qosLevel != 0) {
+                    throw new DecoderException("Illegal BIT 2 or 1 in fixed header of " + messageType
+                            + " message, must be 0, found " + qosLevel);
+                }
+                if (retain) {
+                    throw new DecoderException("Illegal BIT 0 in fixed header of " + messageType
+                            + " message, must be 0, found 1");
+                }
+                break;
+            default:
+                throw new DecoderException("Unknown message type, do not know how to validate fixed header");
+        }
+
        int remainingLength = 0;
        int multiplier = 1;
        short digit;
@@ -163,7 +229,7 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        }
        MqttFixedHeader decodedFixedHeader =
                new MqttFixedHeader(messageType, dupFlag, MqttQoS.valueOf(qosLevel), retain, remainingLength);
-        return validateFixedHeader(resetUnusedFields(decodedFixedHeader));
+        return MqttCodecUtil.validateFixedHeader(ctx, MqttCodecUtil.resetUnusedFields(decodedFixedHeader));
    }

    /**
@@ -172,50 +238,60 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
     * @param mqttFixedHeader MqttFixedHeader of the same message
     * @return the variable header
     */
-    private static Result<?> decodeVariableHeader(ByteBuf buffer, MqttFixedHeader mqttFixedHeader) {
+    private Result<?> decodeVariableHeader(ChannelHandlerContext ctx, ByteBuf buffer, MqttFixedHeader mqttFixedHeader) {
        switch (mqttFixedHeader.messageType()) {
            case CONNECT:
-                return decodeConnectionVariableHeader(buffer);
+                return decodeConnectionVariableHeader(ctx, buffer);

            case CONNACK:
-                return decodeConnAckVariableHeader(buffer);
+                return decodeConnAckVariableHeader(ctx, buffer);

-            case SUBSCRIBE:
            case UNSUBSCRIBE:
+            case SUBSCRIBE:
            case SUBACK:
            case UNSUBACK:
+                return decodeMessageIdAndPropertiesVariableHeader(ctx, buffer);
+
            case PUBACK:
            case PUBREC:
            case PUBCOMP:
            case PUBREL:
-                return decodeMessageIdVariableHeader(buffer);
+                return decodePubReplyMessage(buffer);

            case PUBLISH:
-                return decodePublishVariableHeader(buffer, mqttFixedHeader);
+                return decodePublishVariableHeader(ctx, buffer, mqttFixedHeader);
+
+            case DISCONNECT:
+            case AUTH:
+                return decodeReasonCodeAndPropertiesVariableHeader(buffer);

            case PINGREQ:
            case PINGRESP:
-            case DISCONNECT:
                // Empty variable header
                return new Result<Object>(null, 0);
+            default:
+                //shouldn't reach here
+                throw new DecoderException("Unknown message type: " + mqttFixedHeader.messageType());
        }
-        return new Result<Object>(null, 0); //should never reach here
    }

-    private static Result<MqttConnectVariableHeader> decodeConnectionVariableHeader(ByteBuf buffer) {
+    private static Result<MqttConnectVariableHeader> decodeConnectionVariableHeader(
+            ChannelHandlerContext ctx,
+            ByteBuf buffer) {
        final Result<String> protoString = decodeString(buffer);
        int numberOfBytesConsumed = protoString.numberOfBytesConsumed;

        final byte protocolLevel = buffer.readByte();
        numberOfBytesConsumed += 1;

-        final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(protoString.value, protocolLevel);
+        MqttVersion version = MqttVersion.fromProtocolNameAndLevel(protoString.value, protocolLevel);
+        MqttCodecUtil.setMqttVersion(ctx, version);

        final int b1 = buffer.readUnsignedByte();
        numberOfBytesConsumed += 1;

-        final Result<Integer> keepAlive = decodeMsbLsb(buffer);
-        numberOfBytesConsumed += keepAlive.numberOfBytesConsumed;
+        final int keepAlive = decodeMsbLsb(buffer);
+        numberOfBytesConsumed += 2;

        final boolean hasUserName = (b1 & 0x80) == 0x80;
        final boolean hasPassword = (b1 & 0x40) == 0x40;
@@ -223,69 +299,178 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        final int willQos = (b1 & 0x18) >> 3;
        final boolean willFlag = (b1 & 0x04) == 0x04;
        final boolean cleanSession = (b1 & 0x02) == 0x02;
-        if (mqttVersion.protocolLevel() >= MqttVersion.MQTT_3_1_1.protocolLevel()) {
+        if (version == MqttVersion.MQTT_3_1_1 || version == MqttVersion.MQTT_5) {
            final boolean zeroReservedFlag = (b1 & 0x01) == 0x0;
            if (!zeroReservedFlag) {
                // MQTT v3.1.1: The Server MUST validate that the reserved flag in the CONNECT Control Packet is
                // set to zero and disconnect the Client if it is not zero.
-                // See http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349230
+                // See https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349230
                throw new DecoderException("non-zero reserved flag");
            }
        }

+        final MqttProperties properties;
+        if (version == MqttVersion.MQTT_5) {
+            final Result<MqttProperties> propertiesResult = decodeProperties(buffer);
+            properties = propertiesResult.value;
+            numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
+        } else {
+            properties = MqttProperties.NO_PROPERTIES;
+        }
+
        final MqttConnectVariableHeader mqttConnectVariableHeader = new MqttConnectVariableHeader(
-                mqttVersion.protocolName(),
-                mqttVersion.protocolLevel(),
+                version.protocolName(),
+                version.protocolLevel(),
                hasUserName,
                hasPassword,
                willRetain,
                willQos,
                willFlag,
                cleanSession,
-                keepAlive.value);
+                keepAlive,
+                properties);
        return new Result<MqttConnectVariableHeader>(mqttConnectVariableHeader, numberOfBytesConsumed);
    }

-    private static Result<MqttConnAckVariableHeader> decodeConnAckVariableHeader(ByteBuf buffer) {
+    private static Result<MqttConnAckVariableHeader> decodeConnAckVariableHeader(
+            ChannelHandlerContext ctx,
+            ByteBuf buffer) {
+        final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
        final boolean sessionPresent = (buffer.readUnsignedByte() & 0x01) == 0x01;
        byte returnCode = buffer.readByte();
-        final int numberOfBytesConsumed = 2;
+        int numberOfBytesConsumed = 2;
+
+        final MqttProperties properties;
+        if (mqttVersion == MqttVersion.MQTT_5) {
+            final Result<MqttProperties> propertiesResult = decodeProperties(buffer);
+            properties = propertiesResult.value;
+            numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
+        } else {
+            properties = MqttProperties.NO_PROPERTIES;
+        }
+
        final MqttConnAckVariableHeader mqttConnAckVariableHeader =
-                new MqttConnAckVariableHeader(MqttConnectReturnCode.valueOf(returnCode), sessionPresent);
+                new MqttConnAckVariableHeader(MqttConnectReturnCode.valueOf(returnCode), sessionPresent, properties);
        return new Result<MqttConnAckVariableHeader>(mqttConnAckVariableHeader, numberOfBytesConsumed);
    }

-    private static Result<MqttMessageIdVariableHeader> decodeMessageIdVariableHeader(ByteBuf buffer) {
-        final Result<Integer> messageId = decodeMessageId(buffer);
-        return new Result<MqttMessageIdVariableHeader>(
-                MqttMessageIdVariableHeader.from(messageId.value),
-                messageId.numberOfBytesConsumed);
+    private static Result<MqttMessageIdAndPropertiesVariableHeader> decodeMessageIdAndPropertiesVariableHeader(
+            ChannelHandlerContext ctx,
+            ByteBuf buffer) {
+        final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+        final int packetId = decodeMessageId(buffer);
+
+        final MqttMessageIdAndPropertiesVariableHeader mqttVariableHeader;
+        final int mqtt5Consumed;
+
+        if (mqttVersion == MqttVersion.MQTT_5) {
+            final Result<MqttProperties> properties = decodeProperties(buffer);
+            mqttVariableHeader = new MqttMessageIdAndPropertiesVariableHeader(packetId, properties.value);
+            mqtt5Consumed = properties.numberOfBytesConsumed;
+        } else {
+            mqttVariableHeader = new MqttMessageIdAndPropertiesVariableHeader(packetId,
+                    MqttProperties.NO_PROPERTIES);
+            mqtt5Consumed = 0;
+        }
+
+        return new Result<MqttMessageIdAndPropertiesVariableHeader>(mqttVariableHeader,
+                2 + mqtt5Consumed);
    }

-    private static Result<MqttPublishVariableHeader> decodePublishVariableHeader(
+    private Result<MqttPubReplyMessageVariableHeader> decodePubReplyMessage(ByteBuf buffer) {
+        final int packetId = decodeMessageId(buffer);
+
+        final MqttPubReplyMessageVariableHeader mqttPubAckVariableHeader;
+        final int consumed;
+        final int packetIdNumberOfBytesConsumed = 2;
+        if (bytesRemainingInVariablePart > 3) {
+            final byte reasonCode = buffer.readByte();
+            final Result<MqttProperties> properties = decodeProperties(buffer);
+            mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
+                    reasonCode,
+                    properties.value);
+            consumed = packetIdNumberOfBytesConsumed + 1 + properties.numberOfBytesConsumed;
+        } else if (bytesRemainingInVariablePart > 2) {
+            final byte reasonCode = buffer.readByte();
+            mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
+                    reasonCode,
+                    MqttProperties.NO_PROPERTIES);
+            consumed = packetIdNumberOfBytesConsumed + 1;
+        } else {
+            mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
+                    (byte) 0,
+                    MqttProperties.NO_PROPERTIES);
+            consumed = packetIdNumberOfBytesConsumed;
+        }
+
+        return new Result<MqttPubReplyMessageVariableHeader>(mqttPubAckVariableHeader, consumed);
+    }
+
+    private Result<MqttReasonCodeAndPropertiesVariableHeader> decodeReasonCodeAndPropertiesVariableHeader(
+            ByteBuf buffer) {
+        final byte reasonCode;
+        final MqttProperties properties;
+        final int consumed;
+        if (bytesRemainingInVariablePart > 1) {
+            reasonCode = buffer.readByte();
+            final Result<MqttProperties> propertiesResult = decodeProperties(buffer);
+            properties = propertiesResult.value;
+            consumed = 1 + propertiesResult.numberOfBytesConsumed;
+        } else if (bytesRemainingInVariablePart > 0) {
+            reasonCode = buffer.readByte();
+            properties = MqttProperties.NO_PROPERTIES;
+            consumed = 1;
+        } else {
+            reasonCode = 0;
+            properties = MqttProperties.NO_PROPERTIES;
+            consumed = 0;
+        }
+        final MqttReasonCodeAndPropertiesVariableHeader mqttReasonAndPropsVariableHeader =
+                new MqttReasonCodeAndPropertiesVariableHeader(reasonCode, properties);
+
+        return new Result<MqttReasonCodeAndPropertiesVariableHeader>(
+                mqttReasonAndPropsVariableHeader,
+                consumed);
+    }
+
+    private Result<MqttPublishVariableHeader> decodePublishVariableHeader(
+            ChannelHandlerContext ctx,
            ByteBuf buffer,
            MqttFixedHeader mqttFixedHeader) {
+        final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
        final Result<String> decodedTopic = decodeString(buffer);
-        if (!isValidPublishTopicName(decodedTopic.value)) {
+        if (!MqttCodecUtil.isValidPublishTopicName(decodedTopic.value)) {
            throw new DecoderException("invalid publish topic name: " + decodedTopic.value + " (contains wildcards)");
        }
        int numberOfBytesConsumed = decodedTopic.numberOfBytesConsumed;

        int messageId = -1;
        if (mqttFixedHeader.qosLevel().value() > 0) {
-            final Result<Integer> decodedMessageId = decodeMessageId(buffer);
-            messageId = decodedMessageId.value;
-            numberOfBytesConsumed += decodedMessageId.numberOfBytesConsumed;
+            messageId = decodeMessageId(buffer);
+            numberOfBytesConsumed += 2;
        }
+
+        final MqttProperties properties;
+        if (mqttVersion == MqttVersion.MQTT_5) {
+            final Result<MqttProperties> propertiesResult = decodeProperties(buffer);
+            properties = propertiesResult.value;
+            numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
+        } else {
+            properties = MqttProperties.NO_PROPERTIES;
+        }
+
        final MqttPublishVariableHeader mqttPublishVariableHeader =
-                new MqttPublishVariableHeader(decodedTopic.value, messageId);
+                new MqttPublishVariableHeader(decodedTopic.value, messageId, properties);
        return new Result<MqttPublishVariableHeader>(mqttPublishVariableHeader, numberOfBytesConsumed);
    }

-    private static Result<Integer> decodeMessageId(ByteBuf buffer) {
-        final Result<Integer> messageId = decodeMsbLsb(buffer);
-        if (!isValidMessageId(messageId.value)) {
-            throw new DecoderException("invalid messageId: " + messageId.value);
+    /**
+     * @return messageId with numberOfBytesConsumed is 2
+     */
+    private static int decodeMessageId(ByteBuf buffer) {
+        final int messageId = decodeMsbLsb(buffer);
+        if (!MqttCodecUtil.isValidMessageId(messageId)) {
+            throw new DecoderException("invalid messageId: " + messageId);
        }
        return messageId;
    }
@@ -300,13 +485,15 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
     * @return the payload
     */
    private static Result<?> decodePayload(
+            ChannelHandlerContext ctx,
            ByteBuf buffer,
            MqttMessageType messageType,
            int bytesRemainingInVariablePart,
+            int maxClientIdLength,
            Object variableHeader) {
        switch (messageType) {
            case CONNECT:
-                return decodeConnectionPayload(buffer, (MqttConnectVariableHeader) variableHeader);
+                return decodeConnectionPayload(buffer, maxClientIdLength, (MqttConnectVariableHeader) variableHeader);

            case SUBSCRIBE:
                return decodeSubscribePayload(buffer, bytesRemainingInVariablePart);
@@ -317,6 +504,9 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
            case UNSUBSCRIBE:
                return decodeUnsubscribePayload(buffer, bytesRemainingInVariablePart);

+            case UNSUBACK:
+                return decodeUnsubAckPayload(ctx, buffer, bytesRemainingInVariablePart);
+
            case PUBLISH:
                return decodePublishPayload(buffer, bytesRemainingInVariablePart);

@@ -328,42 +518,55 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {

    private static Result<MqttConnectPayload> decodeConnectionPayload(
            ByteBuf buffer,
+            int maxClientIdLength,
            MqttConnectVariableHeader mqttConnectVariableHeader) {
        final Result<String> decodedClientId = decodeString(buffer);
        final String decodedClientIdValue = decodedClientId.value;
        final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(mqttConnectVariableHeader.name(),
                (byte) mqttConnectVariableHeader.version());
-        if (!isValidClientId(mqttVersion, decodedClientIdValue)) {
+        if (!MqttCodecUtil.isValidClientId(mqttVersion, maxClientIdLength, decodedClientIdValue)) {
            throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + decodedClientIdValue);
        }
        int numberOfBytesConsumed = decodedClientId.numberOfBytesConsumed;

        Result<String> decodedWillTopic = null;
-        Result<String> decodedWillMessage = null;
+        byte[] decodedWillMessage = null;
+
+        final MqttProperties willProperties;
        if (mqttConnectVariableHeader.isWillFlag()) {
+            if (mqttVersion == MqttVersion.MQTT_5) {
+                final Result<MqttProperties> propertiesResult = decodeProperties(buffer);
+                willProperties = propertiesResult.value;
+                numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
+            } else {
+                willProperties = MqttProperties.NO_PROPERTIES;
+            }
            decodedWillTopic = decodeString(buffer, 0, 32767);
            numberOfBytesConsumed += decodedWillTopic.numberOfBytesConsumed;
-            decodedWillMessage = decodeAsciiString(buffer);
-            numberOfBytesConsumed += decodedWillMessage.numberOfBytesConsumed;
+            decodedWillMessage = decodeByteArray(buffer);
+            numberOfBytesConsumed += decodedWillMessage.length + 2;
+        } else {
+            willProperties = MqttProperties.NO_PROPERTIES;
        }
        Result<String> decodedUserName = null;
-        Result<byte[]> decodedPassword = null;
+        byte[] decodedPassword = null;
        if (mqttConnectVariableHeader.hasUserName()) {
            decodedUserName = decodeString(buffer);
            numberOfBytesConsumed += decodedUserName.numberOfBytesConsumed;
        }
        if (mqttConnectVariableHeader.hasPassword()) {
-            decodedPassword = decodeByte(buffer);
-            numberOfBytesConsumed += decodedPassword.numberOfBytesConsumed;
+            decodedPassword = decodeByteArray(buffer);
+            numberOfBytesConsumed += decodedPassword.length + 2;
        }

        final MqttConnectPayload mqttConnectPayload =
                new MqttConnectPayload(
                        decodedClientId.value,
+                        willProperties,
                        decodedWillTopic != null ? decodedWillTopic.value : null,
-                        decodedWillMessage != null ? decodedWillMessage.value : null,
+                        decodedWillMessage,
                        decodedUserName != null ? decodedUserName.value : null,
-                        decodedPassword != null ? decodedPassword.value : null);
+                        decodedPassword);
        return new Result<MqttConnectPayload>(mqttConnectPayload, numberOfBytesConsumed);
    }

@@ -375,9 +578,21 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
            final Result<String> decodedTopicName = decodeString(buffer);
            numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
-            int qos = buffer.readUnsignedByte() & 0x03;
+            //See 3.8.3.1 Subscription Options of MQTT 5.0 specification for optionByte details
+            final short optionByte = buffer.readUnsignedByte();
+
+            MqttQoS qos = MqttQoS.valueOf(optionByte & 0x03);
+            boolean noLocal = ((optionByte & 0x04) >> 2) == 1;
+            boolean retainAsPublished = ((optionByte & 0x08) >> 3) == 1;
+            MqttSubscriptionOption.RetainedHandlingPolicy retainHandling = MqttSubscriptionOption.RetainedHandlingPolicy.valueOf((optionByte & 0x30) >> 4);
+
+            final MqttSubscriptionOption subscriptionOption = new MqttSubscriptionOption(qos,
+                    noLocal,
+                    retainAsPublished,
+                    retainHandling);
+
            numberOfBytesConsumed++;
-            subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, MqttQoS.valueOf(qos)));
+            subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, subscriptionOption));
        }
        return new Result<MqttSubscribePayload>(new MqttSubscribePayload(subscribeTopics), numberOfBytesConsumed);
    }
@@ -385,16 +600,30 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
    private static Result<MqttSubAckPayload> decodeSubackPayload(
            ByteBuf buffer,
            int bytesRemainingInVariablePart) {
-        final List<Integer> grantedQos = new ArrayList<Integer>();
+        final List<Integer> grantedQos = new ArrayList<Integer>(bytesRemainingInVariablePart);
        int numberOfBytesConsumed = 0;
        while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
-            int qos = buffer.readUnsignedByte() & 0x03;
+            int reasonCode = buffer.readUnsignedByte();
            numberOfBytesConsumed++;
-            grantedQos.add(qos);
+            grantedQos.add(reasonCode);
        }
        return new Result<MqttSubAckPayload>(new MqttSubAckPayload(grantedQos), numberOfBytesConsumed);
    }

+    private static Result<MqttUnsubAckPayload> decodeUnsubAckPayload(
+        ChannelHandlerContext ctx,
+        ByteBuf buffer,
+        int bytesRemainingInVariablePart) {
+        final List<Short> reasonCodes = new ArrayList<Short>(bytesRemainingInVariablePart);
+        int numberOfBytesConsumed = 0;
+        while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
+            short reasonCode = buffer.readUnsignedByte();
+            numberOfBytesConsumed++;
+            reasonCodes.add(reasonCode);
+        }
+        return new Result<MqttUnsubAckPayload>(new MqttUnsubAckPayload(reasonCodes), numberOfBytesConsumed);
+    }
+
    private static Result<MqttUnsubscribePayload> decodeUnsubscribePayload(
            ByteBuf buffer,
            int bytesRemainingInVariablePart) {
@@ -419,25 +648,9 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        return decodeString(buffer, 0, Integer.MAX_VALUE);
    }

-    private static Result<String> decodeAsciiString(ByteBuf buffer) {
-        Result<String> result = decodeString(buffer, 0, Integer.MAX_VALUE);
-        final String s = result.value;
-        for (int i = 0; i < s.length(); i++) {
-            if (s.charAt(i) > 127) {
-                return new Result<String>(null, result.numberOfBytesConsumed);
-            }
-        }
-        return new Result<String>(s, result.numberOfBytesConsumed);
-    }
-
-    private static Result<byte[]> decodeByte(ByteBuf buffer) {
-        return decodeByte(buffer, 0, Integer.MAX_VALUE);
-    }
-
    private static Result<String> decodeString(ByteBuf buffer, int minBytes, int maxBytes) {
-        final Result<Integer> decodedSize = decodeMsbLsb(buffer);
-        int size = decodedSize.value;
-        int numberOfBytesConsumed = decodedSize.numberOfBytesConsumed;
+        int size = decodeMsbLsb(buffer);
+        int numberOfBytesConsumed = 2;
        if (size < minBytes || size > maxBytes) {
            buffer.skipBytes(size);
            numberOfBytesConsumed += size;
@@ -449,35 +662,68 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
        return new Result<String>(s, numberOfBytesConsumed);
    }

-    private static Result<byte[]> decodeByte(ByteBuf buffer, int minBytes, int maxBytes) {
-        final Result<Integer> decodedSize = decodeMsbLsb(buffer);
-        int size = decodedSize.value;
-        int numberOfBytesConsumed = decodedSize.numberOfBytesConsumed;
-        if (size < minBytes || size > maxBytes) {
-            buffer.skipBytes(size);
-            numberOfBytesConsumed += size;
-            return new Result<>(null, numberOfBytesConsumed);
-        }
-        byte[] s = new byte[size];
-        buffer.getBytes(buffer.readerIndex(), s, 0, size);
-        buffer.skipBytes(size);
-        numberOfBytesConsumed += size;
-        return new Result<>(s, numberOfBytesConsumed);
+    /**
+     *
+     * @return the decoded byte[], numberOfBytesConsumed = byte[].length + 2
+     */
+    private static byte[] decodeByteArray(ByteBuf buffer) {
+        int size = decodeMsbLsb(buffer);
+        byte[] bytes = new byte[size];
+        buffer.readBytes(bytes);
+        return bytes;
    }

-    private static Result<Integer> decodeMsbLsb(ByteBuf buffer) {
-        return decodeMsbLsb(buffer, 0, 65535);
+    // packing utils to reduce the amount of garbage while decoding ints
+    private static long packInts(int a, int b) {
+        return (((long) a) << 32) | (b & 0xFFFFFFFFL);
    }

-    private static Result<Integer> decodeMsbLsb(ByteBuf buffer, int min, int max) {
+    private static int unpackA(long ints) {
+        return (int) (ints >> 32);
+    }
+
+    private static int unpackB(long ints) {
+        return (int) ints;
+    }
+
+    /**
+     *  numberOfBytesConsumed = 2. return decoded result.
+     */
+    private static int decodeMsbLsb(ByteBuf buffer) {
+        int min = 0;
+        int max = 65535;
        short msbSize = buffer.readUnsignedByte();
        short lsbSize = buffer.readUnsignedByte();
-        final int numberOfBytesConsumed = 2;
        int result = msbSize << 8 | lsbSize;
        if (result < min || result > max) {
            result = -1;
        }
-        return new Result<Integer>(result, numberOfBytesConsumed);
+        return result;
+    }
+
+    /**
+     * See 1.5.5 Variable Byte Integer section of MQTT 5.0 specification for encoding/decoding rules
+     *
+     * @param buffer the buffer to decode from
+     * @return result pack with a = decoded integer, b = numberOfBytesConsumed. Need to unpack to read them.
+     * @throws DecoderException if bad MQTT protocol limits Remaining Length
+     */
+    private static long decodeVariableByteInteger(ByteBuf buffer) {
+        int remainingLength = 0;
+        int multiplier = 1;
+        short digit;
+        int loops = 0;
+        do {
+            digit = buffer.readUnsignedByte();
+            remainingLength += (digit & 127) * multiplier;
+            multiplier *= 128;
+            loops++;
+        } while ((digit & 128) != 0 && loops < 4);
+
+        if (loops == 4 && (digit & 128) != 0) {
+            throw new DecoderException("MQTT protocol limits Remaining Length to 4 bytes");
+        }
+        return packInts(remainingLength, loops);
    }

    private static final class Result<T> {
@@ -490,4 +736,82 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
            this.numberOfBytesConsumed = numberOfBytesConsumed;
        }
    }
+
+    private static Result<MqttProperties> decodeProperties(ByteBuf buffer) {
+        final long propertiesLength = decodeVariableByteInteger(buffer);
+        int totalPropertiesLength = unpackA(propertiesLength);
+        int numberOfBytesConsumed = unpackB(propertiesLength);
+
+        MqttProperties decodedProperties = new MqttProperties();
+        while (numberOfBytesConsumed < totalPropertiesLength) {
+            long propertyId = decodeVariableByteInteger(buffer);
+            final int propertyIdValue = unpackA(propertyId);
+            numberOfBytesConsumed += unpackB(propertyId);
+            MqttProperties.MqttPropertyType propertyType = MqttProperties.MqttPropertyType.valueOf(propertyIdValue);
+            switch (propertyType) {
+                case PAYLOAD_FORMAT_INDICATOR:
+                case REQUEST_PROBLEM_INFORMATION:
+                case REQUEST_RESPONSE_INFORMATION:
+                case MAXIMUM_QOS:
+                case RETAIN_AVAILABLE:
+                case WILDCARD_SUBSCRIPTION_AVAILABLE:
+                case SUBSCRIPTION_IDENTIFIER_AVAILABLE:
+                case SHARED_SUBSCRIPTION_AVAILABLE:
+                    final int b1 = buffer.readUnsignedByte();
+                    numberOfBytesConsumed++;
+                    decodedProperties.add(new MqttProperties.IntegerProperty(propertyIdValue, b1));
+                    break;
+                case SERVER_KEEP_ALIVE:
+                case RECEIVE_MAXIMUM:
+                case TOPIC_ALIAS_MAXIMUM:
+                case TOPIC_ALIAS:
+                    final int int2BytesResult = decodeMsbLsb(buffer);
+                    numberOfBytesConsumed += 2;
+                    decodedProperties.add(new MqttProperties.IntegerProperty(propertyIdValue, int2BytesResult));
+                    break;
+                case PUBLICATION_EXPIRY_INTERVAL:
+                case SESSION_EXPIRY_INTERVAL:
+                case WILL_DELAY_INTERVAL:
+                case MAXIMUM_PACKET_SIZE:
+                    final int maxPacketSize = buffer.readInt();
+                    numberOfBytesConsumed += 4;
+                    decodedProperties.add(new MqttProperties.IntegerProperty(propertyIdValue, maxPacketSize));
+                    break;
+                case SUBSCRIPTION_IDENTIFIER:
+                    long vbIntegerResult = decodeVariableByteInteger(buffer);
+                    numberOfBytesConsumed += unpackB(vbIntegerResult);
+                    decodedProperties.add(new MqttProperties.IntegerProperty(propertyIdValue, unpackA(vbIntegerResult)));
+                    break;
+                case CONTENT_TYPE:
+                case RESPONSE_TOPIC:
+                case ASSIGNED_CLIENT_IDENTIFIER:
+                case AUTHENTICATION_METHOD:
+                case RESPONSE_INFORMATION:
+                case SERVER_REFERENCE:
+                case REASON_STRING:
+                    final Result<String> stringResult = decodeString(buffer);
+                    numberOfBytesConsumed += stringResult.numberOfBytesConsumed;
+                    decodedProperties.add(new MqttProperties.StringProperty(propertyIdValue, stringResult.value));
+                    break;
+                case USER_PROPERTY:
+                    final Result<String> keyResult = decodeString(buffer);
+                    final Result<String> valueResult = decodeString(buffer);
+                    numberOfBytesConsumed += keyResult.numberOfBytesConsumed;
+                    numberOfBytesConsumed += valueResult.numberOfBytesConsumed;
+                    decodedProperties.add(new MqttProperties.UserProperty(keyResult.value, valueResult.value));
+                    break;
+                case CORRELATION_DATA:
+                case AUTHENTICATION_DATA:
+                    final byte[] binaryDataResult = decodeByteArray(buffer);
+                    numberOfBytesConsumed += binaryDataResult.length + 2;
+                    decodedProperties.add(new MqttProperties.BinaryProperty(propertyIdValue, binaryDataResult));
+                    break;
+                default:
+                    //shouldn't reach here
+                    throw new DecoderException("Unknown property type: " + propertyType);
+            }
+        }
+
+        return new Result<MqttProperties>(decodedProperties, numberOfBytesConsumed);
+    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -18,19 +18,22 @@ package io.netty.handler.codec.mqtt;

 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.EncoderException;
 import io.netty.handler.codec.MessageToMessageEncoder;
-import io.netty.util.CharsetUtil;
 import io.netty.util.internal.EmptyArrays;

 import java.util.List;

-import static io.netty.handler.codec.mqtt.MqttCodecUtil.*;
+import static io.netty.buffer.ByteBufUtil.*;

 /**
 * Encodes Mqtt messages into bytes following the protocol specification v3.1
- * as described here <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html">MQTTV3.1</a>
+ * as described here <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html">MQTTV3.1</a>
+ * or v5.0 as described here <a href="https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html">MQTTv5.0</a> -
+ * depending on the version specified in the first CONNECT message that goes through the channel.
 */
@ChannelHandler.Sharable
 public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
@@ -41,49 +44,57 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {

    @Override
    protected void encode(ChannelHandlerContext ctx, MqttMessage msg, List<Object> out) throws Exception {
-        out.add(doEncode(ctx.alloc(), msg));
+        out.add(doEncode(ctx, msg));
    }

    /**
     * This is the main encoding method.
     * It's only visible for testing.
     *
-     * @param byteBufAllocator Allocates ByteBuf
     * @param message MQTT message to encode
     * @return ByteBuf with encoded bytes
     */
-    static ByteBuf doEncode(ByteBufAllocator byteBufAllocator, MqttMessage message) {
+    static ByteBuf doEncode(ChannelHandlerContext ctx,
+                     MqttMessage message) {

        switch (message.fixedHeader().messageType()) {
            case CONNECT:
-                return encodeConnectMessage(byteBufAllocator, (MqttConnectMessage) message);
+                return encodeConnectMessage(ctx, (MqttConnectMessage) message);

            case CONNACK:
-                return encodeConnAckMessage(byteBufAllocator, (MqttConnAckMessage) message);
+                return encodeConnAckMessage(ctx, (MqttConnAckMessage) message);

            case PUBLISH:
-                return encodePublishMessage(byteBufAllocator, (MqttPublishMessage) message);
+                return encodePublishMessage(ctx, (MqttPublishMessage) message);

            case SUBSCRIBE:
-                return encodeSubscribeMessage(byteBufAllocator, (MqttSubscribeMessage) message);
+                return encodeSubscribeMessage(ctx, (MqttSubscribeMessage) message);

            case UNSUBSCRIBE:
-                return encodeUnsubscribeMessage(byteBufAllocator, (MqttUnsubscribeMessage) message);
+                return encodeUnsubscribeMessage(ctx,  (MqttUnsubscribeMessage) message);

            case SUBACK:
-                return encodeSubAckMessage(byteBufAllocator, (MqttSubAckMessage) message);
+                return encodeSubAckMessage(ctx, (MqttSubAckMessage) message);

            case UNSUBACK:
+                if (message instanceof MqttUnsubAckMessage) {
+                    return encodeUnsubAckMessage(ctx, (MqttUnsubAckMessage) message);
+                }
+                return encodeMessageWithOnlySingleByteFixedHeaderAndMessageId(ctx.alloc(), message);
+
            case PUBACK:
            case PUBREC:
            case PUBREL:
            case PUBCOMP:
-                return encodeMessageWithOnlySingleByteFixedHeaderAndMessageId(byteBufAllocator, message);
+                return encodePubReplyMessage(ctx, message);
+
+            case DISCONNECT:
+            case AUTH:
+                return encodeReasonCodePlusPropertiesMessage(ctx, message);

            case PINGREQ:
            case PINGRESP:
-            case DISCONNECT:
-                return encodeMessageWithOnlySingleByteFixedHeader(byteBufAllocator, message);
+                return encodeMessageWithOnlySingleByteFixedHeader(ctx.alloc(), message);

            default:
                throw new IllegalArgumentException(
@@ -92,7 +103,7 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
    }

    private static ByteBuf encodeConnectMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttConnectMessage message) {
        int payloadBufferSize = 0;

@@ -101,70 +112,96 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        MqttConnectPayload payload = message.payload();
        MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(variableHeader.name(),
                (byte) variableHeader.version());
+        MqttCodecUtil.setMqttVersion(ctx, mqttVersion);
+
+        // as MQTT 3.1 & 3.1.1 spec, If the User Name Flag is set to 0, the Password Flag MUST be set to 0
+        if (!variableHeader.hasUserName() && variableHeader.hasPassword()) {
+            throw new EncoderException("Without a username, the password MUST be not set");
+        }

        // Client id
        String clientIdentifier = payload.clientIdentifier();
-        if (!isValidClientId(mqttVersion, clientIdentifier)) {
+        if (!MqttCodecUtil.isValidClientId(mqttVersion, MqttConstant.DEFAULT_MAX_CLIENT_ID_LENGTH, clientIdentifier)) {
            throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + clientIdentifier);
        }
-        byte[] clientIdentifierBytes = encodeStringUtf8(clientIdentifier);
-        payloadBufferSize += 2 + clientIdentifierBytes.length;
+        int clientIdentifierBytes = utf8Bytes(clientIdentifier);
+        payloadBufferSize += 2 + clientIdentifierBytes;

        // Will topic and message
        String willTopic = payload.willTopic();
-        byte[] willTopicBytes = willTopic != null ? encodeStringUtf8(willTopic) : EmptyArrays.EMPTY_BYTES;
-        String willMessage = payload.willMessage();
-        byte[] willMessageBytes = willMessage != null ? encodeStringUtf8(willMessage) : EmptyArrays.EMPTY_BYTES;
+        int willTopicBytes = nullableUtf8Bytes(willTopic);
+        byte[] willMessage = payload.willMessageInBytes();
+        byte[] willMessageBytes = willMessage != null ? willMessage : EmptyArrays.EMPTY_BYTES;
        if (variableHeader.isWillFlag()) {
-            payloadBufferSize += 2 + willTopicBytes.length;
+            payloadBufferSize += 2 + willTopicBytes;
            payloadBufferSize += 2 + willMessageBytes.length;
        }

        String userName = payload.userName();
-        byte[] userNameBytes = userName != null ? encodeStringUtf8(userName) : EmptyArrays.EMPTY_BYTES;
+        int userNameBytes = nullableUtf8Bytes(userName);
        if (variableHeader.hasUserName()) {
-            payloadBufferSize += 2 + userNameBytes.length;
+            payloadBufferSize += 2 + userNameBytes;
        }

-        byte[] passwordBytes = payload.password();
+        byte[] password = payload.passwordInBytes();
+        byte[] passwordBytes = password != null ? password : EmptyArrays.EMPTY_BYTES;
        if (variableHeader.hasPassword()) {
            payloadBufferSize += 2 + passwordBytes.length;
        }

-        // Fixed header
+        // Fixed and variable header
        byte[] protocolNameBytes = mqttVersion.protocolNameBytes();
-        int variableHeaderBufferSize = 2 + protocolNameBytes.length + 4;
-        int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
-        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
-        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variablePartSize);
-        buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
-        writeVariableLengthInt(buf, variablePartSize);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(
+                mqttVersion,
+                ctx.alloc(),
+                message.variableHeader().properties());
+        try {
+            final ByteBuf willPropertiesBuf;
+            if (variableHeader.isWillFlag()) {
+                willPropertiesBuf = encodePropertiesIfNeeded(mqttVersion, ctx.alloc(), payload.willProperties());
+                payloadBufferSize += willPropertiesBuf.readableBytes();
+            } else {
+                willPropertiesBuf = Unpooled.EMPTY_BUFFER;
+            }
+            try {
+                int variableHeaderBufferSize = 2 + protocolNameBytes.length + 4 + propertiesBuf.readableBytes();

-        buf.writeShort(protocolNameBytes.length);
-        buf.writeBytes(protocolNameBytes);
+                int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+                int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+                ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+                buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+                writeVariableLengthInt(buf, variablePartSize);

-        buf.writeByte(variableHeader.version());
-        buf.writeByte(getConnVariableHeaderFlag(variableHeader));
-        buf.writeShort(variableHeader.keepAliveTimeSeconds());
+                buf.writeShort(protocolNameBytes.length);
+                buf.writeBytes(protocolNameBytes);

-        // Payload
-        buf.writeShort(clientIdentifierBytes.length);
-        buf.writeBytes(clientIdentifierBytes, 0, clientIdentifierBytes.length);
-        if (variableHeader.isWillFlag()) {
-            buf.writeShort(willTopicBytes.length);
-            buf.writeBytes(willTopicBytes, 0, willTopicBytes.length);
-            buf.writeShort(willMessageBytes.length);
-            buf.writeBytes(willMessageBytes, 0, willMessageBytes.length);
+                buf.writeByte(variableHeader.version());
+                buf.writeByte(getConnVariableHeaderFlag(variableHeader));
+                buf.writeShort(variableHeader.keepAliveTimeSeconds());
+                buf.writeBytes(propertiesBuf);
+
+                // Payload
+                writeExactUTF8String(buf, clientIdentifier, clientIdentifierBytes);
+                if (variableHeader.isWillFlag()) {
+                    buf.writeBytes(willPropertiesBuf);
+                    writeExactUTF8String(buf, willTopic, willTopicBytes);
+                    buf.writeShort(willMessageBytes.length);
+                    buf.writeBytes(willMessageBytes, 0, willMessageBytes.length);
+                }
+                if (variableHeader.hasUserName()) {
+                    writeExactUTF8String(buf, userName, userNameBytes);
+                }
+                if (variableHeader.hasPassword()) {
+                    buf.writeShort(passwordBytes.length);
+                    buf.writeBytes(passwordBytes, 0, passwordBytes.length);
+                }
+                return buf;
+            } finally {
+                willPropertiesBuf.release();
+            }
+        } finally {
+            propertiesBuf.release();
        }
-        if (variableHeader.hasUserName()) {
-            buf.writeShort(userNameBytes.length);
-            buf.writeBytes(userNameBytes, 0, userNameBytes.length);
-        }
-        if (variableHeader.hasPassword()) {
-            buf.writeShort(passwordBytes.length);
-            buf.writeBytes(passwordBytes, 0, passwordBytes.length);
-        }
-        return buf;
    }

    private static int getConnVariableHeaderFlag(MqttConnectVariableHeader variableHeader) {
@@ -189,149 +226,285 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
    }

    private static ByteBuf encodeConnAckMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttConnAckMessage message) {
-        int length = 4;
-        MqttConnectAckPayload payload = null;
-        if (message.payload() != null) {
-            payload = (MqttConnectAckPayload)message.payload();
-            if (payload.getData() != null && payload.getData().length > 0) {
-                length += payload.getData().length;
-            }
-        }
-        ByteBuf buf = byteBufAllocator.buffer(length);
-        buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
-        buf.writeByte(length - 2);
-        buf.writeByte(message.variableHeader().isSessionPresent() ? 0x01 : 0x00);
-        buf.writeByte(message.variableHeader().connectReturnCode().byteValue());
-        if (length > 4) {
-            buf.writeBytes(payload.getData());
-        }
+        final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                ctx.alloc(),
+                message.variableHeader().properties());

-        return buf;
+        try {
+            int length = 4;
+            MqttConnectAckPayload payload = null;
+            if (message.payload() != null) {
+                payload = (MqttConnectAckPayload)message.payload();
+                if (payload.getData() != null && payload.getData().length > 0) {
+                    length += payload.getData().length;
+                }
+            }
+            ByteBuf buf = ctx.alloc().buffer(length + propertiesBuf.readableBytes());
+            buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
+            writeVariableLengthInt(buf, length - 2 + propertiesBuf.readableBytes());
+            buf.writeByte(message.variableHeader().isSessionPresent() ? 0x01 : 0x00);
+            buf.writeByte(message.variableHeader().connectReturnCode().byteValue());
+            if (length > 4) {
+                buf.writeBytes(payload.getData());
+            }
+            buf.writeBytes(propertiesBuf);
+            return buf;
+        } finally {
+            propertiesBuf.release();
+        }
    }

    private static ByteBuf encodeSubscribeMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttSubscribeMessage message) {
-        int variableHeaderBufferSize = 2;
-        int payloadBufferSize = 0;
+        MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                ctx.alloc(),
+                message.idAndPropertiesVariableHeader().properties());

-        MqttFixedHeader mqttFixedHeader = message.fixedHeader();
-        MqttMessageIdVariableHeader variableHeader = message.variableHeader();
-        MqttSubscribePayload payload = message.payload();
+        try {
+            final int variableHeaderBufferSize = 2 + propertiesBuf.readableBytes();
+            int payloadBufferSize = 0;

-        for (MqttTopicSubscription topic : payload.topicSubscriptions()) {
-            String topicName = topic.topicName();
-            byte[] topicNameBytes = encodeStringUtf8(topicName);
-            payloadBufferSize += 2 + topicNameBytes.length;
-            payloadBufferSize += 1;
+            MqttFixedHeader mqttFixedHeader = message.fixedHeader();
+            MqttMessageIdVariableHeader variableHeader = message.variableHeader();
+            MqttSubscribePayload payload = message.payload();
+
+            for (MqttTopicSubscription topic : payload.topicSubscriptions()) {
+                String topicName = topic.topicName();
+                int topicNameBytes = utf8Bytes(topicName);
+                payloadBufferSize += 2 + topicNameBytes;
+                payloadBufferSize += 1;
+            }
+
+            int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+            int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+
+            ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+            buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+            writeVariableLengthInt(buf, variablePartSize);
+
+            // Variable Header
+            int messageId = variableHeader.messageId();
+            buf.writeShort(messageId);
+            buf.writeBytes(propertiesBuf);
+
+            // Payload
+            for (MqttTopicSubscription topic : payload.topicSubscriptions()) {
+                writeUnsafeUTF8String(buf, topic.topicName());
+                if (mqttVersion.protocolLevel() >= MqttVersion.MQTT_3_1_1.protocolLevel()) {
+                    buf.writeByte(topic.qualityOfService().value());
+                } else {
+                    final MqttSubscriptionOption option = topic.option();
+
+                    int optionEncoded = option.retainHandling().value() << 4;
+                    if (option.isRetainAsPublished()) {
+                        optionEncoded |= 0x08;
+                    }
+                    if (option.isNoLocal()) {
+                        optionEncoded |= 0x04;
+                    }
+                    optionEncoded |= option.qos().value();
+
+                    buf.writeByte(optionEncoded);
+                }
+            }
+
+            return buf;
+        } finally {
+            propertiesBuf.release();
        }
-
-        int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
-        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
-
-        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variablePartSize);
-        buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
-        writeVariableLengthInt(buf, variablePartSize);
-
-        // Variable Header
-        int messageId = variableHeader.messageId();
-        buf.writeShort(messageId);
-
-        // Payload
-        for (MqttTopicSubscription topic : payload.topicSubscriptions()) {
-            String topicName = topic.topicName();
-            byte[] topicNameBytes = encodeStringUtf8(topicName);
-            buf.writeShort(topicNameBytes.length);
-            buf.writeBytes(topicNameBytes, 0, topicNameBytes.length);
-            buf.writeByte(topic.qualityOfService().value());
-        }
-
-        return buf;
    }

    private static ByteBuf encodeUnsubscribeMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttUnsubscribeMessage message) {
-        int variableHeaderBufferSize = 2;
-        int payloadBufferSize = 0;
+        MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                ctx.alloc(),
+                message.idAndPropertiesVariableHeader().properties());

-        MqttFixedHeader mqttFixedHeader = message.fixedHeader();
-        MqttMessageIdVariableHeader variableHeader = message.variableHeader();
-        MqttUnsubscribePayload payload = message.payload();
+        try {
+            final int variableHeaderBufferSize = 2 + propertiesBuf.readableBytes();
+            int payloadBufferSize = 0;

-        for (String topicName : payload.topics()) {
-            byte[] topicNameBytes = encodeStringUtf8(topicName);
-            payloadBufferSize += 2 + topicNameBytes.length;
+            MqttFixedHeader mqttFixedHeader = message.fixedHeader();
+            MqttMessageIdVariableHeader variableHeader = message.variableHeader();
+            MqttUnsubscribePayload payload = message.payload();
+
+            for (String topicName : payload.topics()) {
+                int topicNameBytes = utf8Bytes(topicName);
+                payloadBufferSize += 2 + topicNameBytes;
+            }
+
+            int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+            int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+
+            ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+            buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+            writeVariableLengthInt(buf, variablePartSize);
+
+            // Variable Header
+            int messageId = variableHeader.messageId();
+            buf.writeShort(messageId);
+            buf.writeBytes(propertiesBuf);
+
+            // Payload
+            for (String topicName : payload.topics()) {
+                writeUnsafeUTF8String(buf, topicName);
+            }
+
+            return buf;
+        } finally {
+            propertiesBuf.release();
        }
-
-        int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
-        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
-
-        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variablePartSize);
-        buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
-        writeVariableLengthInt(buf, variablePartSize);
-
-        // Variable Header
-        int messageId = variableHeader.messageId();
-        buf.writeShort(messageId);
-
-        // Payload
-        for (String topicName : payload.topics()) {
-            byte[] topicNameBytes = encodeStringUtf8(topicName);
-            buf.writeShort(topicNameBytes.length);
-            buf.writeBytes(topicNameBytes, 0, topicNameBytes.length);
-        }
-
-        return buf;
    }

    private static ByteBuf encodeSubAckMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttSubAckMessage message) {
-        int variableHeaderBufferSize = 2;
-        int payloadBufferSize = message.payload().grantedQoSLevels().size();
-        int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
-        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
-        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variablePartSize);
-        buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
-        writeVariableLengthInt(buf, variablePartSize);
-        buf.writeShort(message.variableHeader().messageId());
-        for (int qos : message.payload().grantedQoSLevels()) {
-            buf.writeByte(qos);
-        }
+        MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                ctx.alloc(),
+                message.idAndPropertiesVariableHeader().properties());
+        try {
+            int variableHeaderBufferSize = 2 + propertiesBuf.readableBytes();
+            int payloadBufferSize = message.payload().grantedQoSLevels().size();
+            int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+            int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+            ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+            buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
+            writeVariableLengthInt(buf, variablePartSize);
+            buf.writeShort(message.variableHeader().messageId());
+            buf.writeBytes(propertiesBuf);
+            for (int code: message.payload().reasonCodes()) {
+                buf.writeByte(code);
+            }

-        return buf;
+            return buf;
+        } finally {
+            propertiesBuf.release();
+        }
+    }
+
+    private static ByteBuf encodeUnsubAckMessage(
+            ChannelHandlerContext ctx,
+            MqttUnsubAckMessage message) {
+        if (message.variableHeader() instanceof  MqttMessageIdAndPropertiesVariableHeader) {
+            MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+            ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                    ctx.alloc(),
+                    message.idAndPropertiesVariableHeader().properties());
+            try {
+                int variableHeaderBufferSize = 2 + propertiesBuf.readableBytes();
+                MqttUnsubAckPayload payload = message.payload();
+                int payloadBufferSize = payload == null ? 0 : payload.unsubscribeReasonCodes().size();
+                int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+                int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+                ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+                buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
+                writeVariableLengthInt(buf, variablePartSize);
+                buf.writeShort(message.variableHeader().messageId());
+                buf.writeBytes(propertiesBuf);
+
+                if (payload != null) {
+                    for (Short reasonCode : payload.unsubscribeReasonCodes()) {
+                        buf.writeByte(reasonCode);
+                    }
+                }
+
+                return buf;
+            } finally {
+                propertiesBuf.release();
+            }
+        } else {
+            return encodeMessageWithOnlySingleByteFixedHeaderAndMessageId(ctx.alloc(), message);
+        }
    }

    private static ByteBuf encodePublishMessage(
-            ByteBufAllocator byteBufAllocator,
+            ChannelHandlerContext ctx,
            MqttPublishMessage message) {
+        MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
        MqttFixedHeader mqttFixedHeader = message.fixedHeader();
        MqttPublishVariableHeader variableHeader = message.variableHeader();
        ByteBuf payload = message.payload().duplicate();

        String topicName = variableHeader.topicName();
-        byte[] topicNameBytes = encodeStringUtf8(topicName);
+        int topicNameBytes = utf8Bytes(topicName);

-        int variableHeaderBufferSize = 2 + topicNameBytes.length +
-                (mqttFixedHeader.qosLevel().value() > 0 ? 2 : 0);
-        int payloadBufferSize = payload.readableBytes();
-        int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
-        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+        ByteBuf propertiesBuf = encodePropertiesIfNeeded(mqttVersion,
+                ctx.alloc(),
+                message.variableHeader().properties());

-        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variablePartSize);
-        buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
-        writeVariableLengthInt(buf, variablePartSize);
-        buf.writeShort(topicNameBytes.length);
-        buf.writeBytes(topicNameBytes);
-        if (mqttFixedHeader.qosLevel().value() > 0) {
-            buf.writeShort(variableHeader.messageId());
+        try {
+            int variableHeaderBufferSize = 2 + topicNameBytes +
+                    (mqttFixedHeader.qosLevel().value() > 0 ? 2 : 0) + propertiesBuf.readableBytes();
+            int payloadBufferSize = payload.readableBytes();
+            int variablePartSize = variableHeaderBufferSize + payloadBufferSize;
+            int fixedHeaderBufferSize = 1 + getVariableLengthInt(variablePartSize);
+
+            ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variablePartSize);
+            buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+            writeVariableLengthInt(buf, variablePartSize);
+            writeExactUTF8String(buf, topicName, topicNameBytes);
+            if (mqttFixedHeader.qosLevel().value() > 0) {
+                buf.writeShort(variableHeader.packetId());
+            }
+            buf.writeBytes(propertiesBuf);
+            buf.writeBytes(payload);
+
+            return buf;
+        } finally {
+            propertiesBuf.release();
        }
-        buf.writeBytes(payload);
+    }

-        return buf;
+    private static ByteBuf encodePubReplyMessage(ChannelHandlerContext ctx,
+                                          MqttMessage message) {
+        if (message.variableHeader() instanceof MqttPubReplyMessageVariableHeader) {
+            MqttFixedHeader mqttFixedHeader = message.fixedHeader();
+            MqttPubReplyMessageVariableHeader variableHeader =
+                    (MqttPubReplyMessageVariableHeader) message.variableHeader();
+            int msgId = variableHeader.messageId();
+
+            final ByteBuf propertiesBuf;
+            final boolean includeReasonCode;
+            final int variableHeaderBufferSize;
+            final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+            if (mqttVersion == MqttVersion.MQTT_5 &&
+                    (variableHeader.reasonCode() != MqttPubReplyMessageVariableHeader.REASON_CODE_OK ||
+                            !variableHeader.properties().isEmpty())) {
+                propertiesBuf = encodeProperties(ctx.alloc(), variableHeader.properties());
+                includeReasonCode = true;
+                variableHeaderBufferSize = 3 + propertiesBuf.readableBytes();
+            } else {
+                propertiesBuf = Unpooled.EMPTY_BUFFER;
+                includeReasonCode = false;
+                variableHeaderBufferSize = 2;
+            }
+
+            try {
+                final int fixedHeaderBufferSize = 1 + getVariableLengthInt(variableHeaderBufferSize);
+                ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variableHeaderBufferSize);
+                buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+                writeVariableLengthInt(buf, variableHeaderBufferSize);
+                buf.writeShort(msgId);
+                if (includeReasonCode) {
+                    buf.writeByte(variableHeader.reasonCode());
+                }
+                buf.writeBytes(propertiesBuf);
+
+                return buf;
+            } finally {
+                propertiesBuf.release();
+            }
+        } else {
+            return encodeMessageWithOnlySingleByteFixedHeaderAndMessageId(ctx.alloc(), message);
+        }
    }

    private static ByteBuf encodeMessageWithOnlySingleByteFixedHeaderAndMessageId(
@@ -342,12 +515,11 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        int msgId = variableHeader.messageId();

        int variableHeaderBufferSize = 2; // variable part only has a message id
-        
        ByteBuf payload = null;
        if (message.payload() != null) {
        	payload = ((ByteBuf)message.payload()).duplicate();
        	variableHeaderBufferSize += payload.readableBytes();
-		}
+		    }
        int fixedHeaderBufferSize = 1 + getVariableLengthInt(variableHeaderBufferSize);
        ByteBuf buf = byteBufAllocator.buffer(fixedHeaderBufferSize + variableHeaderBufferSize);
        buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
@@ -355,11 +527,53 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        buf.writeShort(msgId);
        if (payload != null) {
        	buf.writeBytes(payload);
-		}
-
+		    }
        return buf;
    }

+    private static ByteBuf encodeReasonCodePlusPropertiesMessage(
+            ChannelHandlerContext ctx,
+            MqttMessage message) {
+        if (message.variableHeader() instanceof MqttReasonCodeAndPropertiesVariableHeader) {
+            MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
+            MqttFixedHeader mqttFixedHeader = message.fixedHeader();
+            MqttReasonCodeAndPropertiesVariableHeader variableHeader =
+                    (MqttReasonCodeAndPropertiesVariableHeader) message.variableHeader();
+
+            final ByteBuf propertiesBuf;
+            final boolean includeReasonCode;
+            final int variableHeaderBufferSize;
+            if (mqttVersion == MqttVersion.MQTT_5 &&
+                    (variableHeader.reasonCode() != MqttReasonCodeAndPropertiesVariableHeader.REASON_CODE_OK ||
+                            !variableHeader.properties().isEmpty())) {
+                propertiesBuf = encodeProperties(ctx.alloc(), variableHeader.properties());
+                includeReasonCode = true;
+                variableHeaderBufferSize = 1 + propertiesBuf.readableBytes();
+            } else {
+                propertiesBuf = Unpooled.EMPTY_BUFFER;
+                includeReasonCode = false;
+                variableHeaderBufferSize = 0;
+            }
+
+            try {
+                final int fixedHeaderBufferSize = 1 + getVariableLengthInt(variableHeaderBufferSize);
+                ByteBuf buf = ctx.alloc().buffer(fixedHeaderBufferSize + variableHeaderBufferSize);
+                buf.writeByte(getFixedHeaderByte1(mqttFixedHeader));
+                writeVariableLengthInt(buf, variableHeaderBufferSize);
+                if (includeReasonCode) {
+                    buf.writeByte(variableHeader.reasonCode());
+                }
+                buf.writeBytes(propertiesBuf);
+
+                return buf;
+            } finally {
+                propertiesBuf.release();
+            }
+        } else {
+            return encodeMessageWithOnlySingleByteFixedHeader(ctx.alloc(), message);
+        }
+    }
+
    private static ByteBuf encodeMessageWithOnlySingleByteFixedHeader(
            ByteBufAllocator byteBufAllocator,
            MqttMessage message) {
@@ -371,6 +585,104 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        return buf;
    }

+    private static ByteBuf encodePropertiesIfNeeded(MqttVersion mqttVersion,
+                                             ByteBufAllocator byteBufAllocator,
+                                             MqttProperties mqttProperties) {
+        if (mqttVersion == MqttVersion.MQTT_5) {
+            return encodeProperties(byteBufAllocator, mqttProperties);
+        }
+        return Unpooled.EMPTY_BUFFER;
+    }
+
+    private static ByteBuf encodeProperties(ByteBufAllocator byteBufAllocator,
+                                            MqttProperties mqttProperties) {
+        ByteBuf propertiesHeaderBuf = byteBufAllocator.buffer();
+        // encode also the Properties part
+        try {
+            ByteBuf propertiesBuf = byteBufAllocator.buffer();
+            try {
+                for (MqttProperties.MqttProperty property : mqttProperties.listAll()) {
+                    MqttProperties.MqttPropertyType propertyType =
+                            MqttProperties.MqttPropertyType.valueOf(property.propertyId);
+                    switch (propertyType) {
+                        case PAYLOAD_FORMAT_INDICATOR:
+                        case REQUEST_PROBLEM_INFORMATION:
+                        case REQUEST_RESPONSE_INFORMATION:
+                        case MAXIMUM_QOS:
+                        case RETAIN_AVAILABLE:
+                        case WILDCARD_SUBSCRIPTION_AVAILABLE:
+                        case SUBSCRIPTION_IDENTIFIER_AVAILABLE:
+                        case SHARED_SUBSCRIPTION_AVAILABLE:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            final byte bytePropValue = ((MqttProperties.IntegerProperty) property).value.byteValue();
+                            propertiesBuf.writeByte(bytePropValue);
+                            break;
+                        case SERVER_KEEP_ALIVE:
+                        case RECEIVE_MAXIMUM:
+                        case TOPIC_ALIAS_MAXIMUM:
+                        case TOPIC_ALIAS:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            final short twoBytesInPropValue =
+                                    ((MqttProperties.IntegerProperty) property).value.shortValue();
+                            propertiesBuf.writeShort(twoBytesInPropValue);
+                            break;
+                        case PUBLICATION_EXPIRY_INTERVAL:
+                        case SESSION_EXPIRY_INTERVAL:
+                        case WILL_DELAY_INTERVAL:
+                        case MAXIMUM_PACKET_SIZE:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            final int fourBytesIntPropValue = ((MqttProperties.IntegerProperty) property).value;
+                            propertiesBuf.writeInt(fourBytesIntPropValue);
+                            break;
+                        case SUBSCRIPTION_IDENTIFIER:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            final int vbi = ((MqttProperties.IntegerProperty) property).value;
+                            writeVariableLengthInt(propertiesBuf, vbi);
+                            break;
+                        case CONTENT_TYPE:
+                        case RESPONSE_TOPIC:
+                        case ASSIGNED_CLIENT_IDENTIFIER:
+                        case AUTHENTICATION_METHOD:
+                        case RESPONSE_INFORMATION:
+                        case SERVER_REFERENCE:
+                        case REASON_STRING:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            writeEagerUTF8String(propertiesBuf, ((MqttProperties.StringProperty) property).value);
+                            break;
+                        case USER_PROPERTY:
+                            final List<MqttProperties.StringPair> pairs =
+                                    ((MqttProperties.UserProperties) property).value;
+                            for (MqttProperties.StringPair pair : pairs) {
+                                writeVariableLengthInt(propertiesBuf, property.propertyId);
+                                writeEagerUTF8String(propertiesBuf, pair.key);
+                                writeEagerUTF8String(propertiesBuf, pair.value);
+                            }
+                            break;
+                        case CORRELATION_DATA:
+                        case AUTHENTICATION_DATA:
+                            writeVariableLengthInt(propertiesBuf, property.propertyId);
+                            final byte[] binaryPropValue = ((MqttProperties.BinaryProperty) property).value;
+                            propertiesBuf.writeShort(binaryPropValue.length);
+                            propertiesBuf.writeBytes(binaryPropValue, 0, binaryPropValue.length);
+                            break;
+                        default:
+                            //shouldn't reach here
+                            throw new EncoderException("Unknown property type: " + propertyType);
+                    }
+                }
+                writeVariableLengthInt(propertiesHeaderBuf, propertiesBuf.readableBytes());
+                propertiesHeaderBuf.writeBytes(propertiesBuf);
+
+                return propertiesHeaderBuf;
+            } finally {
+                propertiesBuf.release();
+            }
+        } catch (RuntimeException e) {
+            propertiesHeaderBuf.release();
+            throw e;
+        }
+    }
+
    private static int getFixedHeaderByte1(MqttFixedHeader header) {
        int ret = 0;
        ret |= header.messageType().value() << 4;
@@ -395,6 +707,42 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        } while (num > 0);
    }

+    private static int nullableUtf8Bytes(String s) {
+        return s == null? 0 : utf8Bytes(s);
+    }
+
+    private static int nullableMaxUtf8Bytes(String s) {
+        return s == null? 0 : utf8MaxBytes(s);
+    }
+
+    private static void writeExactUTF8String(ByteBuf buf, String s, int utf8Length) {
+        buf.ensureWritable(utf8Length + 2);
+        buf.writeShort(utf8Length);
+        if (utf8Length > 0) {
+            final int writtenUtf8Length = reserveAndWriteUtf8(buf, s, utf8Length);
+            assert writtenUtf8Length == utf8Length;
+        }
+    }
+
+    private static void writeEagerUTF8String(ByteBuf buf, String s) {
+        final int maxUtf8Length = nullableMaxUtf8Bytes(s);
+        buf.ensureWritable(maxUtf8Length + 2);
+        final int writerIndex = buf.writerIndex();
+        final int startUtf8String = writerIndex + 2;
+        buf.writerIndex(startUtf8String);
+        final int utf8Length = s != null? reserveAndWriteUtf8(buf, s, maxUtf8Length) : 0;
+        buf.setShort(writerIndex, utf8Length);
+    }
+
+    private static void writeUnsafeUTF8String(ByteBuf buf, String s) {
+        final int writerIndex = buf.writerIndex();
+        final int startUtf8String = writerIndex + 2;
+        // no need to reserve any capacity here, already done earlier: that's why is Unsafe
+        buf.writerIndex(startUtf8String);
+        final int utf8Length = s != null? reserveAndWriteUtf8(buf, s, 0) : 0;
+        buf.setShort(writerIndex, utf8Length);
+    }
+
    private static int getVariableLengthInt(int num) {
        int count = 0;
        do {
@@ -404,7 +752,4 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
        return count;
    }

-    private static byte[] encodeStringUtf8(String s) {
-      return s.getBytes(CharsetUtil.UTF_8);
-    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -20,7 +20,7 @@ import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.StringUtil;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#fixed-header">
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#fixed-header">
 *     MQTTV3.1/fixed-header</a>
 */
 public final class MqttFixedHeader {
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -29,6 +29,17 @@ public class MqttMessage {
    private final Object payload;
    private final DecoderResult decoderResult;

+    // Constants for fixed-header only message types with all flags set to 0 (see
+    // https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Table_2.2_-)
+    public static final MqttMessage PINGREQ = new MqttMessage(new MqttFixedHeader(MqttMessageType.PINGREQ, false,
+            MqttQoS.AT_MOST_ONCE, false, 0));
+
+    public static final MqttMessage PINGRESP = new MqttMessage(new MqttFixedHeader(MqttMessageType.PINGRESP, false,
+            MqttQoS.AT_MOST_ONCE, false, 0));
+
+    public static final MqttMessage DISCONNECT = new MqttMessage(new MqttFixedHeader(MqttMessageType.DISCONNECT, false,
+            MqttQoS.AT_MOST_ONCE, false, 0));
+
    public MqttMessage(MqttFixedHeader mqttFixedHeader) {
        this(mqttFixedHeader, null, null);
    }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -15,10 +15,14 @@
 */
 package io.netty.handler.codec.mqtt;

+import static io.netty.util.internal.ObjectUtil.checkPositive;
+
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import io.netty.util.CharsetUtil;

 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;

 public final class MqttMessageBuilders {
@@ -29,6 +33,7 @@ public final class MqttMessageBuilders {
        private MqttQoS qos;
        private ByteBuf payload;
        private int messageId;
+        private MqttProperties mqttProperties;

        PublishBuilder() {
        }
@@ -58,9 +63,15 @@ public final class MqttMessageBuilders {
            return this;
        }

+        public PublishBuilder properties(MqttProperties properties) {
+            this.mqttProperties = properties;
+            return this;
+        }
+
        public MqttPublishMessage build() {
            MqttFixedHeader mqttFixedHeader = new MqttFixedHeader(MqttMessageType.PUBLISH, false, qos, retained, 0);
-            MqttPublishVariableHeader mqttVariableHeader = new MqttPublishVariableHeader(topic, messageId);
+            MqttPublishVariableHeader mqttVariableHeader =
+                    new MqttPublishVariableHeader(topic, messageId, mqttProperties);
            return new MqttPublishMessage(mqttFixedHeader, mqttVariableHeader, Unpooled.buffer().writeBytes(payload));
        }
    }
@@ -73,13 +84,15 @@ public final class MqttMessageBuilders {
        private boolean hasUser;
        private boolean hasPassword;
        private int keepAliveSecs;
+        private MqttProperties willProperties = MqttProperties.NO_PROPERTIES;
        private boolean willFlag;
        private boolean willRetain;
        private MqttQoS willQos = MqttQoS.AT_MOST_ONCE;
        private String willTopic;
-        private String willMessage;
+        private byte[] willMessage;
        private String username;
        private byte[] password;
+        private MqttProperties properties = MqttProperties.NO_PROPERTIES;

        ConnectBuilder() {
        }
@@ -119,7 +132,16 @@ public final class MqttMessageBuilders {
            return this;
        }

+        /**
+         * @deprecated use {@link ConnectBuilder#willMessage(byte[])} instead
+         */
+        @Deprecated
        public ConnectBuilder willMessage(String willMessage) {
+            willMessage(willMessage == null ? null : willMessage.getBytes(CharsetUtil.UTF_8));
+            return this;
+        }
+
+        public ConnectBuilder willMessage(byte[] willMessage) {
            this.willMessage = willMessage;
            return this;
        }
@@ -129,6 +151,11 @@ public final class MqttMessageBuilders {
            return this;
        }

+        public ConnectBuilder willProperties(MqttProperties willProperties) {
+            this.willProperties = willProperties;
+            return this;
+        }
+
        public ConnectBuilder hasUser(boolean value) {
            this.hasUser = value;
            return this;
@@ -140,17 +167,31 @@ public final class MqttMessageBuilders {
        }

        public ConnectBuilder username(String username) {
-            this.hasUser = true;
+            this.hasUser = username != null;
            this.username = username;
            return this;
        }

+        /**
+         * @deprecated use {@link ConnectBuilder#password(byte[])} instead
+         */
+        @Deprecated
+        public ConnectBuilder password(String password) {
+            password(password == null ? null : password.getBytes(CharsetUtil.UTF_8));
+            return this;
+        }
+
        public ConnectBuilder password(byte[] password) {
-            this.hasPassword = true;
+            this.hasPassword = password != null;
            this.password = password;
            return this;
        }

+        public ConnectBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
        public MqttConnectMessage build() {
            MqttFixedHeader mqttFixedHeader =
                    new MqttFixedHeader(MqttMessageType.CONNECT, false, MqttQoS.AT_MOST_ONCE, false, 0);
@@ -164,9 +205,10 @@ public final class MqttMessageBuilders {
                            willQos.value(),
                            willFlag,
                            cleanSession,
-                            keepAliveSecs);
+                            keepAliveSecs,
+                            properties);
            MqttConnectPayload mqttConnectPayload =
-                    new MqttConnectPayload(clientId, willTopic, willMessage, username, password);
+                    new MqttConnectPayload(clientId, willProperties, willTopic, willMessage, username, password);
            return new MqttConnectMessage(mqttFixedHeader, mqttConnectVariableHeader, mqttConnectPayload);
        }
    }
@@ -175,36 +217,54 @@ public final class MqttMessageBuilders {

        private List<MqttTopicSubscription> subscriptions;
        private int messageId;
+        private MqttProperties properties;

        SubscribeBuilder() {
        }

        public SubscribeBuilder addSubscription(MqttQoS qos, String topic) {
-            if (subscriptions == null) {
-                subscriptions = new ArrayList<MqttTopicSubscription>(5);
-            }
+            ensureSubscriptionsExist();
            subscriptions.add(new MqttTopicSubscription(topic, qos));
            return this;
        }

+        public SubscribeBuilder addSubscription(String topic, MqttSubscriptionOption option) {
+            ensureSubscriptionsExist();
+            subscriptions.add(new MqttTopicSubscription(topic, option));
+            return this;
+        }
+
        public SubscribeBuilder messageId(int messageId) {
            this.messageId = messageId;
            return this;
        }

+        public SubscribeBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
        public MqttSubscribeMessage build() {
            MqttFixedHeader mqttFixedHeader =
                    new MqttFixedHeader(MqttMessageType.SUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE, false, 0);
-            MqttMessageIdVariableHeader mqttVariableHeader = MqttMessageIdVariableHeader.from(messageId);
+            MqttMessageIdAndPropertiesVariableHeader mqttVariableHeader =
+                    new MqttMessageIdAndPropertiesVariableHeader(messageId, properties);
            MqttSubscribePayload mqttSubscribePayload = new MqttSubscribePayload(subscriptions);
            return new MqttSubscribeMessage(mqttFixedHeader, mqttVariableHeader, mqttSubscribePayload);
        }
+
+        private void ensureSubscriptionsExist() {
+            if (subscriptions == null) {
+                subscriptions = new ArrayList<MqttTopicSubscription>(5);
+            }
+        }
    }

    public static final class UnsubscribeBuilder {

        private List<String> topicFilters;
        private int messageId;
+        private MqttProperties properties;

        UnsubscribeBuilder() {
        }
@@ -222,21 +282,33 @@ public final class MqttMessageBuilders {
            return this;
        }

+        public UnsubscribeBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
        public MqttUnsubscribeMessage build() {
            MqttFixedHeader mqttFixedHeader =
                    new MqttFixedHeader(MqttMessageType.UNSUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE, false, 0);
-            MqttMessageIdVariableHeader mqttVariableHeader = MqttMessageIdVariableHeader.from(messageId);
+            MqttMessageIdAndPropertiesVariableHeader mqttVariableHeader =
+                    new MqttMessageIdAndPropertiesVariableHeader(messageId, properties);
            MqttUnsubscribePayload mqttSubscribePayload = new MqttUnsubscribePayload(topicFilters);
            return new MqttUnsubscribeMessage(mqttFixedHeader, mqttVariableHeader, mqttSubscribePayload);
        }
    }

+    public interface PropertiesInitializer<T> {
+        void apply(T builder);
+    }
+
    public static final class ConnAckBuilder {

        private MqttConnectReturnCode returnCode;
        private boolean sessionPresent;
+        private MqttProperties properties = MqttProperties.NO_PROPERTIES;
+        private ConnAckPropertiesBuilder propsBuilder;

-        ConnAckBuilder() {
+        private ConnAckBuilder() {
        }

        public ConnAckBuilder returnCode(MqttConnectReturnCode returnCode) {
@@ -249,15 +321,402 @@ public final class MqttMessageBuilders {
            return this;
        }

+        public ConnAckBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public ConnAckBuilder properties(PropertiesInitializer<ConnAckPropertiesBuilder> consumer) {
+            if (propsBuilder == null) {
+                propsBuilder = new ConnAckPropertiesBuilder();
+            }
+            consumer.apply(propsBuilder);
+            return this;
+        }
+
        public MqttConnAckMessage build() {
+            if (propsBuilder != null) {
+                properties = propsBuilder.build();
+            }
            MqttFixedHeader mqttFixedHeader =
                    new MqttFixedHeader(MqttMessageType.CONNACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
            MqttConnAckVariableHeader mqttConnAckVariableHeader =
-                    new MqttConnAckVariableHeader(returnCode, sessionPresent);
+                    new MqttConnAckVariableHeader(returnCode, sessionPresent, properties);
            return new MqttConnAckMessage(mqttFixedHeader, mqttConnAckVariableHeader);
        }
    }

+    public static final class ConnAckPropertiesBuilder {
+        private String clientId;
+        private Long sessionExpiryInterval;
+        private int receiveMaximum;
+        private Byte maximumQos;
+        private boolean retain;
+        private Long maximumPacketSize;
+        private int topicAliasMaximum;
+        private String reasonString;
+        private final MqttProperties.UserProperties userProperties = new MqttProperties.UserProperties();
+        private Boolean wildcardSubscriptionAvailable;
+        private Boolean subscriptionIdentifiersAvailable;
+        private Boolean sharedSubscriptionAvailable;
+        private Integer serverKeepAlive;
+        private String responseInformation;
+        private String serverReference;
+        private String authenticationMethod;
+        private byte[] authenticationData;
+
+        public MqttProperties build() {
+            final MqttProperties props = new MqttProperties();
+            if (clientId != null) {
+                props.add(new MqttProperties.StringProperty(MqttProperties.MqttPropertyType.ASSIGNED_CLIENT_IDENTIFIER.value(),
+                        clientId));
+            }
+            if (sessionExpiryInterval != null) {
+                props.add(new MqttProperties.IntegerProperty(
+                        MqttProperties.MqttPropertyType.SESSION_EXPIRY_INTERVAL.value(), sessionExpiryInterval.intValue()));
+            }
+            if (receiveMaximum > 0) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.RECEIVE_MAXIMUM.value(), receiveMaximum));
+            }
+            if (maximumQos != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.MAXIMUM_QOS.value(), receiveMaximum));
+            }
+            props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.RETAIN_AVAILABLE.value(), retain ? 1 : 0));
+            if (maximumPacketSize != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.MAXIMUM_PACKET_SIZE.value(),
+                        maximumPacketSize.intValue()));
+            }
+            props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.TOPIC_ALIAS_MAXIMUM.value(),
+                    topicAliasMaximum));
+            if (reasonString != null) {
+                props.add(new MqttProperties.StringProperty(MqttProperties.MqttPropertyType.REASON_STRING.value(), reasonString));
+            }
+            props.add(userProperties);
+            if (wildcardSubscriptionAvailable != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.WILDCARD_SUBSCRIPTION_AVAILABLE.value(),
+                        wildcardSubscriptionAvailable ? 1 : 0));
+            }
+            if (subscriptionIdentifiersAvailable != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.SUBSCRIPTION_IDENTIFIER_AVAILABLE.value(),
+                        subscriptionIdentifiersAvailable ? 1 : 0));
+            }
+            if (sharedSubscriptionAvailable != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.SHARED_SUBSCRIPTION_AVAILABLE.value(),
+                        sharedSubscriptionAvailable ? 1 : 0));
+            }
+            if (serverKeepAlive != null) {
+                props.add(new MqttProperties.IntegerProperty(MqttProperties.MqttPropertyType.SERVER_KEEP_ALIVE.value(),
+                        serverKeepAlive));
+            }
+            if (responseInformation != null) {
+                props.add(new MqttProperties.StringProperty(MqttProperties.MqttPropertyType.RESPONSE_INFORMATION.value(),
+                        responseInformation));
+            }
+            if (serverReference != null) {
+                props.add(new MqttProperties.StringProperty(MqttProperties.MqttPropertyType.SERVER_REFERENCE.value(),
+                        serverReference));
+            }
+            if (authenticationMethod != null) {
+                props.add(new MqttProperties.StringProperty(MqttProperties.MqttPropertyType.AUTHENTICATION_METHOD.value(),
+                        authenticationMethod));
+            }
+            if (authenticationData != null) {
+                props.add(new MqttProperties.BinaryProperty(MqttProperties.MqttPropertyType.AUTHENTICATION_DATA.value(),
+                        authenticationData));
+            }
+
+            return props;
+        }
+
+        public ConnAckPropertiesBuilder sessionExpiryInterval(long seconds) {
+            this.sessionExpiryInterval = seconds;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder receiveMaximum(int value) {
+            this.receiveMaximum = checkPositive(value, "value");
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder maximumQos(byte value) {
+            if (value != 0 && value != 1) {
+                throw new IllegalArgumentException("maximum QoS property could be 0 or 1");
+            }
+            this.maximumQos = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder retainAvailable(boolean retain) {
+            this.retain = retain;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder maximumPacketSize(long size) {
+            this.maximumPacketSize = checkPositive(size, "size");
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder assignedClientId(String clientId) {
+            this.clientId = clientId;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder topicAliasMaximum(int value) {
+            this.topicAliasMaximum = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder reasonString(String reason) {
+            this.reasonString = reason;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder userProperty(String name, String value) {
+            userProperties.add(name, value);
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder wildcardSubscriptionAvailable(boolean value) {
+            this.wildcardSubscriptionAvailable = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder subscriptionIdentifiersAvailable(boolean value) {
+            this.subscriptionIdentifiersAvailable = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder sharedSubscriptionAvailable(boolean value) {
+            this.sharedSubscriptionAvailable = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder serverKeepAlive(int seconds) {
+            this.serverKeepAlive = seconds;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder responseInformation(String value) {
+            this.responseInformation = value;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder serverReference(String host) {
+            this.serverReference = host;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder authenticationMethod(String methodName) {
+            this.authenticationMethod = methodName;
+            return this;
+        }
+
+        public ConnAckPropertiesBuilder authenticationData(byte[] rawData) {
+            this.authenticationData = rawData.clone();
+            return this;
+        }
+    }
+
+    public static final class PubAckBuilder {
+
+        private int packetId;
+        private byte reasonCode;
+        private MqttProperties properties;
+
+        PubAckBuilder() {
+        }
+
+        public PubAckBuilder reasonCode(byte reasonCode) {
+            this.reasonCode = reasonCode;
+            return this;
+        }
+
+        public PubAckBuilder packetId(int packetId) {
+            this.packetId = packetId;
+            return this;
+        }
+
+        /**
+         * @deprecated use {@link PubAckBuilder#packetId(int)} instead
+         */
+        @Deprecated
+        public PubAckBuilder packetId(short packetId) {
+            return packetId(packetId & 0xFFFF);
+        }
+
+        public PubAckBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public MqttMessage build() {
+            MqttFixedHeader mqttFixedHeader =
+                    new MqttFixedHeader(MqttMessageType.PUBACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
+            MqttPubReplyMessageVariableHeader mqttPubAckVariableHeader =
+                    new MqttPubReplyMessageVariableHeader(packetId, reasonCode, properties);
+            return new MqttMessage(mqttFixedHeader, mqttPubAckVariableHeader);
+        }
+    }
+
+    public static final class SubAckBuilder {
+
+        private int packetId;
+        private MqttProperties properties;
+        private final List<MqttQoS> grantedQoses = new ArrayList<MqttQoS>();
+
+        SubAckBuilder() {
+        }
+
+        public SubAckBuilder packetId(int packetId) {
+            this.packetId = packetId;
+            return this;
+        }
+
+        /**
+         * @deprecated use {@link SubAckBuilder#packetId(int)} instead
+         */
+        @Deprecated
+        public SubAckBuilder packetId(short packetId) {
+            return packetId(packetId & 0xFFFF);
+        }
+
+        public SubAckBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public SubAckBuilder addGrantedQos(MqttQoS qos) {
+            this.grantedQoses.add(qos);
+            return this;
+        }
+
+        public SubAckBuilder addGrantedQoses(MqttQoS... qoses) {
+            this.grantedQoses.addAll(Arrays.asList(qoses));
+            return this;
+        }
+
+        public MqttSubAckMessage build() {
+            MqttFixedHeader mqttFixedHeader =
+                    new MqttFixedHeader(MqttMessageType.SUBACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
+            MqttMessageIdAndPropertiesVariableHeader mqttSubAckVariableHeader =
+                    new MqttMessageIdAndPropertiesVariableHeader(packetId, properties);
+
+            //transform to primitive types
+            int[] grantedQoses = new int[this.grantedQoses.size()];
+            int i = 0;
+            for (MqttQoS grantedQos : this.grantedQoses) {
+                grantedQoses[i++] = grantedQos.value();
+            }
+
+            MqttSubAckPayload subAckPayload = new MqttSubAckPayload(grantedQoses);
+            return new MqttSubAckMessage(mqttFixedHeader, mqttSubAckVariableHeader, subAckPayload);
+        }
+    }
+
+    public static final class UnsubAckBuilder {
+
+        private int packetId;
+        private MqttProperties properties;
+        private final List<Short> reasonCodes = new ArrayList<Short>();
+
+        UnsubAckBuilder() {
+        }
+
+        public UnsubAckBuilder packetId(int packetId) {
+            this.packetId = packetId;
+            return this;
+        }
+
+        /**
+         * @deprecated use {@link UnsubAckBuilder#packetId(int)} instead
+         */
+        @Deprecated
+        public UnsubAckBuilder packetId(short packetId) {
+            return packetId(packetId & 0xFFFF);
+        }
+
+        public UnsubAckBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public UnsubAckBuilder addReasonCode(short reasonCode) {
+            this.reasonCodes.add(reasonCode);
+            return this;
+        }
+
+        public UnsubAckBuilder addReasonCodes(Short... reasonCodes) {
+            this.reasonCodes.addAll(Arrays.asList(reasonCodes));
+            return this;
+        }
+
+        public MqttUnsubAckMessage build() {
+            MqttFixedHeader mqttFixedHeader =
+                    new MqttFixedHeader(MqttMessageType.UNSUBACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
+            MqttMessageIdAndPropertiesVariableHeader mqttSubAckVariableHeader =
+                    new MqttMessageIdAndPropertiesVariableHeader(packetId, properties);
+
+            MqttUnsubAckPayload subAckPayload = new MqttUnsubAckPayload(reasonCodes);
+            return new MqttUnsubAckMessage(mqttFixedHeader, mqttSubAckVariableHeader, subAckPayload);
+        }
+    }
+
+    public static final class DisconnectBuilder {
+
+        private MqttProperties properties;
+        private byte reasonCode;
+
+        DisconnectBuilder() {
+        }
+
+        public DisconnectBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public DisconnectBuilder reasonCode(byte reasonCode) {
+            this.reasonCode = reasonCode;
+            return this;
+        }
+
+        public MqttMessage build() {
+            MqttFixedHeader mqttFixedHeader =
+                    new MqttFixedHeader(MqttMessageType.DISCONNECT, false, MqttQoS.AT_MOST_ONCE, false, 0);
+            MqttReasonCodeAndPropertiesVariableHeader mqttDisconnectVariableHeader =
+                    new MqttReasonCodeAndPropertiesVariableHeader(reasonCode, properties);
+
+            return new MqttMessage(mqttFixedHeader, mqttDisconnectVariableHeader);
+        }
+    }
+
+    public static final class AuthBuilder {
+
+        private MqttProperties properties;
+        private byte reasonCode;
+
+        AuthBuilder() {
+        }
+
+        public AuthBuilder properties(MqttProperties properties) {
+            this.properties = properties;
+            return this;
+        }
+
+        public AuthBuilder reasonCode(byte reasonCode) {
+            this.reasonCode = reasonCode;
+            return this;
+        }
+
+        public MqttMessage build() {
+            MqttFixedHeader mqttFixedHeader =
+                    new MqttFixedHeader(MqttMessageType.AUTH, false, MqttQoS.AT_MOST_ONCE, false, 0);
+            MqttReasonCodeAndPropertiesVariableHeader mqttAuthVariableHeader =
+                    new MqttReasonCodeAndPropertiesVariableHeader(reasonCode, properties);
+
+            return new MqttMessage(mqttFixedHeader, mqttAuthVariableHeader);
+        }
+    }
+
    public static ConnectBuilder connect() {
        return new ConnectBuilder();
    }
@@ -278,6 +737,26 @@ public final class MqttMessageBuilders {
        return new UnsubscribeBuilder();
    }

+    public static PubAckBuilder pubAck() {
+        return new PubAckBuilder();
+    }
+
+    public static SubAckBuilder subAck() {
+        return new SubAckBuilder();
+    }
+
+    public static UnsubAckBuilder unsubAck() {
+        return new UnsubAckBuilder();
+    }
+
+    public static DisconnectBuilder disconnect() {
+        return new DisconnectBuilder();
+    }
+
+    public static AuthBuilder auth() {
+        return new AuthBuilder();
+    }
+
    private MqttMessageBuilders() {
    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -50,7 +50,8 @@ public final class MqttMessageFactory {
            case UNSUBACK:
                return new MqttUnsubAckMessage(
                        mqttFixedHeader,
-                        (MqttMessageIdVariableHeader) variableHeader);
+                        (MqttMessageIdVariableHeader) variableHeader,
+                        (MqttUnsubAckPayload) payload);

            case UNSUBSCRIBE:
                return new MqttUnsubscribeMessage(
@@ -65,17 +66,24 @@ public final class MqttMessageFactory {
                        (ByteBuf) payload);

            case PUBACK:
+                //Having MqttPubReplyMessageVariableHeader or MqttMessageIdVariableHeader
                return new MqttPubAckMessage(mqttFixedHeader, (MqttMessageIdVariableHeader) variableHeader);
            case PUBREC:
            case PUBREL:
            case PUBCOMP:
+                //Having MqttPubReplyMessageVariableHeader or MqttMessageIdVariableHeader
                return new MqttMessage(mqttFixedHeader, variableHeader);

            case PINGREQ:
            case PINGRESP:
-            case DISCONNECT:
                return new MqttMessage(mqttFixedHeader);

+            case DISCONNECT:
+            case AUTH:
+                //Having MqttReasonCodeAndPropertiesVariableHeader
+                return new MqttMessage(mqttFixedHeader,
+                        variableHeader);
+
            default:
                throw new IllegalArgumentException("unknown message type: " + mqttFixedHeader.messageType());
        }
@@ -85,5 +93,10 @@ public final class MqttMessageFactory {
        return new MqttMessage(null, null, null, DecoderResult.failure(cause));
    }

+    public static MqttMessage newInvalidMessage(MqttFixedHeader mqttFixedHeader, Object variableHeader,
+                                                Throwable cause) {
+        return new MqttMessage(mqttFixedHeader, variableHeader, null, DecoderResult.failure(cause));
+    }
+
    private MqttMessageFactory() { }
 }
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.handler.codec.mqtt;
+
+import io.netty.util.internal.StringUtil;
+
+/**
+ * Variable Header containing, Packet Id and Properties as in MQTT v5 spec.
+ */
+public final class MqttMessageIdAndPropertiesVariableHeader extends MqttMessageIdVariableHeader {
+
+    private final MqttProperties properties;
+
+    public MqttMessageIdAndPropertiesVariableHeader(int messageId, MqttProperties properties) {
+        super(messageId);
+        if (messageId < 1 || messageId > 0xffff) {
+            throw new IllegalArgumentException("messageId: " + messageId + " (expected: 1 ~ 65535)");
+        }
+        this.properties = MqttProperties.withEmptyDefaults(properties);
+    }
+
+    public MqttProperties properties() {
+        return properties;
+    }
+
+    @Override
+    public String toString() {
+        return StringUtil.simpleClassName(this) + "[" +
+                "messageId=" + messageId() +
+                ", properties=" + properties +
+                ']';
+    }
+
+    @Override
+    MqttMessageIdAndPropertiesVariableHeader withDefaultEmptyProperties() {
+        return this;
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -20,9 +20,9 @@ import io.netty.util.internal.StringUtil;

 /**
 * Variable Header containing only Message Id
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#msg-id">MQTTV3.1/msg-id</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#msg-id">MQTTV3.1/msg-id</a>
 */
-public final class MqttMessageIdVariableHeader {
+public class MqttMessageIdVariableHeader {

    private final int messageId;

@@ -33,7 +33,7 @@ public final class MqttMessageIdVariableHeader {
      return new MqttMessageIdVariableHeader(messageId);
    }

-    private MqttMessageIdVariableHeader(int messageId) {
+    protected MqttMessageIdVariableHeader(int messageId) {
        this.messageId = messageId;
    }

@@ -49,4 +49,12 @@ public final class MqttMessageIdVariableHeader {
            .append(']')
            .toString();
    }
+
+    public MqttMessageIdAndPropertiesVariableHeader withEmptyProperties() {
+        return new MqttMessageIdAndPropertiesVariableHeader(messageId, MqttProperties.NO_PROPERTIES);
+    }
+
+    MqttMessageIdAndPropertiesVariableHeader withDefaultEmptyProperties() {
+        return withEmptyProperties();
+    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -33,7 +33,24 @@ public enum MqttMessageType {
    UNSUBACK(11),
    PINGREQ(12),
    PINGRESP(13),
-    DISCONNECT(14);
+    DISCONNECT(14),
+    AUTH(15);
+
+    private static final MqttMessageType[] VALUES;
+
+    static {
+        // this prevent values to be assigned with the wrong order
+        // and ensure valueOf to work fine
+        final MqttMessageType[] values = values();
+        VALUES = new MqttMessageType[values.length + 1];
+        for (MqttMessageType mqttMessageType : values) {
+            final int value = mqttMessageType.value;
+            if (VALUES[value] != null) {
+                throw new AssertionError("value already in use: " + value);
+            }
+            VALUES[value] = mqttMessageType;
+        }
+    }

    private final int value;

@@ -46,12 +63,10 @@ public enum MqttMessageType {
    }

    public static MqttMessageType valueOf(int type) {
-        for (MqttMessageType t : values()) {
-            if (t.value == type) {
-                return t;
-            }
+        if (type <= 0 || type >= VALUES.length) {
+            throw new IllegalArgumentException("unknown message type: " + type);
        }
-        throw new IllegalArgumentException("unknown message type: " + type);
+        return VALUES[type];
    }
 }

@@ -0,0 +1,414 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.mqtt;
+
+import io.netty.util.collection.IntObjectHashMap;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.ArrayList;
+
+/**
+ * MQTT Properties container
+ * */
+public final class MqttProperties {
+
+    public enum MqttPropertyType {
+        // single byte properties
+        PAYLOAD_FORMAT_INDICATOR(0x01),
+        REQUEST_PROBLEM_INFORMATION(0x17),
+        REQUEST_RESPONSE_INFORMATION(0x19),
+        MAXIMUM_QOS(0x24),
+        RETAIN_AVAILABLE(0x25),
+        WILDCARD_SUBSCRIPTION_AVAILABLE(0x28),
+        SUBSCRIPTION_IDENTIFIER_AVAILABLE(0x29),
+        SHARED_SUBSCRIPTION_AVAILABLE(0x2A),
+
+        // two bytes properties
+        SERVER_KEEP_ALIVE(0x13),
+        RECEIVE_MAXIMUM(0x21),
+        TOPIC_ALIAS_MAXIMUM(0x22),
+        TOPIC_ALIAS(0x23),
+
+        // four bytes properties
+        PUBLICATION_EXPIRY_INTERVAL(0x02),
+        SESSION_EXPIRY_INTERVAL(0x11),
+        WILL_DELAY_INTERVAL(0x18),
+        MAXIMUM_PACKET_SIZE(0x27),
+
+        // Variable Byte Integer
+        SUBSCRIPTION_IDENTIFIER(0x0B),
+
+        // UTF-8 Encoded String properties
+        CONTENT_TYPE(0x03),
+        RESPONSE_TOPIC(0x08),
+        ASSIGNED_CLIENT_IDENTIFIER(0x12),
+        AUTHENTICATION_METHOD(0x15),
+        RESPONSE_INFORMATION(0x1A),
+        SERVER_REFERENCE(0x1C),
+        REASON_STRING(0x1F),
+        USER_PROPERTY(0x26),
+
+        // Binary Data
+        CORRELATION_DATA(0x09),
+        AUTHENTICATION_DATA(0x16);
+
+        private static final MqttPropertyType[] VALUES;
+
+        static {
+            VALUES = new MqttPropertyType[43];
+            for (MqttPropertyType v : values()) {
+                VALUES[v.value] = v;
+            }
+        }
+
+        private final int value;
+
+        MqttPropertyType(int value) {
+            this.value = value;
+        }
+
+        public int value() {
+            return value;
+        }
+
+        public static MqttPropertyType valueOf(int type) {
+            MqttPropertyType t = null;
+            try {
+                t = VALUES[type];
+            } catch (ArrayIndexOutOfBoundsException ignored) {
+                // nop
+            }
+            if (t == null) {
+                throw new IllegalArgumentException("unknown property type: " + type);
+            }
+            return t;
+        }
+    }
+
+    public static final MqttProperties NO_PROPERTIES = new MqttProperties(false);
+
+    static MqttProperties withEmptyDefaults(MqttProperties properties) {
+        if (properties == null) {
+            return MqttProperties.NO_PROPERTIES;
+        }
+        return properties;
+    }
+
+    /**
+     * MQTT property base class
+     *
+     * @param <T> property type
+     */
+    public abstract static class MqttProperty<T> {
+        final T value;
+        final int propertyId;
+
+        protected MqttProperty(int propertyId, T value) {
+            this.propertyId = propertyId;
+            this.value = value;
+        }
+
+        /**
+         * Get MQTT property value
+         *
+         * @return property value
+         */
+        public T value() {
+            return value;
+        }
+
+        /**
+         * Get MQTT property ID
+         * @return property ID
+         */
+        public int propertyId() {
+            return propertyId;
+        }
+
+        @Override
+        public int hashCode() {
+            return propertyId + 31 * value.hashCode();
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (this == obj) {
+                return true;
+            }
+            if (obj == null || getClass() != obj.getClass()) {
+                return false;
+            }
+            MqttProperty that = (MqttProperty) obj;
+            return this.propertyId == that.propertyId && this.value.equals(that.value);
+        }
+    }
+
+    public static final class IntegerProperty extends MqttProperty<Integer> {
+
+        public IntegerProperty(int propertyId, Integer value) {
+            super(propertyId, value);
+        }
+
+        @Override
+        public String toString() {
+            return "IntegerProperty(" + propertyId + ", " + value + ")";
+        }
+    }
+
+    public static final class StringProperty extends MqttProperty<String> {
+
+        public StringProperty(int propertyId, String value) {
+            super(propertyId, value);
+        }
+
+        @Override
+        public String toString() {
+            return "StringProperty(" + propertyId + ", " + value + ")";
+        }
+    }
+
+    public static final class StringPair {
+        public final String key;
+        public final String value;
+
+        public StringPair(String key, String value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        @Override
+        public int hashCode() {
+            return key.hashCode() + 31 * value.hashCode();
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (this == obj) {
+                return true;
+            }
+            if (obj == null || getClass() != obj.getClass()) {
+                return false;
+            }
+            StringPair that = (StringPair) obj;
+
+            return that.key.equals(this.key) && that.value.equals(this.value);
+        }
+    }
+
+    //User properties are the only properties that may be included multiple times and
+    //are the only properties where ordering is required. Therefore, they need a special handling
+    public static final class UserProperties extends MqttProperty<List<StringPair>> {
+        public UserProperties() {
+            super(MqttPropertyType.USER_PROPERTY.value, new ArrayList<StringPair>());
+        }
+
+        /**
+         * Create user properties from the collection of the String pair values
+         *
+         * @param values string pairs. Collection entries are copied, collection itself isn't shared
+         */
+        public UserProperties(Collection<StringPair> values) {
+            this();
+            this.value.addAll(values);
+        }
+
+        private static UserProperties fromUserPropertyCollection(Collection<UserProperty> properties) {
+            UserProperties userProperties = new UserProperties();
+            for (UserProperty property: properties) {
+                userProperties.add(new StringPair(property.value.key, property.value.value));
+            }
+            return userProperties;
+        }
+
+        public void add(StringPair pair) {
+            this.value.add(pair);
+        }
+
+        public void add(String key, String value) {
+            this.value.add(new StringPair(key, value));
+        }
+
+        @Override
+        public String toString() {
+            StringBuilder builder = new StringBuilder("UserProperties(");
+            boolean first = true;
+            for (StringPair pair: value) {
+                if (!first) {
+                    builder.append(", ");
+                }
+                builder.append(pair.key + "->" + pair.value);
+                first = false;
+            }
+            builder.append(")");
+            return builder.toString();
+        }
+    }
+
+    public static final class UserProperty extends MqttProperty<StringPair> {
+        public UserProperty(String key, String value) {
+            super(MqttPropertyType.USER_PROPERTY.value, new StringPair(key, value));
+        }
+
+        @Override
+        public String toString() {
+            return "UserProperty(" + value.key + ", " + value.value + ")";
+        }
+    }
+
+    public static final class BinaryProperty extends MqttProperty<byte[]> {
+
+        public BinaryProperty(int propertyId, byte[] value) {
+            super(propertyId, value);
+        }
+
+        @Override
+        public String toString() {
+            return "BinaryProperty(" + propertyId + ", " + value.length + " bytes)";
+        }
+    }
+
+    public MqttProperties() {
+        this(true);
+    }
+
+    private MqttProperties(boolean canModify) {
+        this.canModify = canModify;
+    }
+
+    private IntObjectHashMap<MqttProperty> props;
+    private List<UserProperty> userProperties;
+    private List<IntegerProperty> subscriptionIds;
+    private final boolean canModify;
+
+    public void add(MqttProperty property) {
+        if (!canModify) {
+            throw new UnsupportedOperationException("adding property isn't allowed");
+        }
+        IntObjectHashMap<MqttProperty> props = this.props;
+        if (property.propertyId == MqttPropertyType.USER_PROPERTY.value) {
+            List<UserProperty> userProperties = this.userProperties;
+            if (userProperties == null) {
+                userProperties = new ArrayList<UserProperty>(1);
+                this.userProperties = userProperties;
+            }
+            if (property instanceof UserProperty) {
+                userProperties.add((UserProperty) property);
+            } else if (property instanceof UserProperties) {
+                for (StringPair pair: ((UserProperties) property).value) {
+                    userProperties.add(new UserProperty(pair.key, pair.value));
+                }
+            } else {
+                throw new IllegalArgumentException("User property must be of UserProperty or UserProperties type");
+            }
+        } else if (property.propertyId == MqttPropertyType.SUBSCRIPTION_IDENTIFIER.value) {
+            List<IntegerProperty> subscriptionIds = this.subscriptionIds;
+            if (subscriptionIds == null) {
+                subscriptionIds = new ArrayList<IntegerProperty>(1);
+                this.subscriptionIds = subscriptionIds;
+            }
+            if (property instanceof IntegerProperty) {
+                subscriptionIds.add((IntegerProperty) property);
+            } else {
+                throw new IllegalArgumentException("Subscription ID must be an integer property");
+            }
+        } else {
+            if (props == null) {
+                props = new IntObjectHashMap<MqttProperty>();
+                this.props = props;
+            }
+            props.put(property.propertyId, property);
+        }
+    }
+
+    public Collection<? extends MqttProperty> listAll() {
+        IntObjectHashMap<MqttProperty> props = this.props;
+        if (props == null && subscriptionIds == null && userProperties == null) {
+            return Collections.<MqttProperty>emptyList();
+        }
+        if (subscriptionIds == null && userProperties == null) {
+            return props.values();
+        }
+        if (props == null && userProperties == null) {
+            return subscriptionIds;
+        }
+        List<MqttProperty> propValues = new ArrayList<MqttProperty>(props != null ? props.size() : 1);
+        if (props != null) {
+            propValues.addAll(props.values());
+        }
+        if (subscriptionIds != null) {
+            propValues.addAll(subscriptionIds);
+        }
+        if (userProperties != null) {
+            propValues.add(UserProperties.fromUserPropertyCollection(userProperties));
+        }
+        return propValues;
+    }
+
+    public boolean isEmpty() {
+        IntObjectHashMap<MqttProperty> props = this.props;
+        return props == null || props.isEmpty();
+    }
+
+    /**
+     * Get property by ID. If there are multiple properties of this type (can be with Subscription ID)
+     * then return the first one.
+     *
+     * @param propertyId ID of the property
+     * @return a property if it is set, null otherwise
+     */
+    public MqttProperty getProperty(int propertyId) {
+        if (propertyId == MqttPropertyType.USER_PROPERTY.value) {
+            //special handling to keep compatibility with earlier versions
+            List<UserProperty> userProperties = this.userProperties;
+            if (userProperties == null) {
+                return null;
+            }
+            return UserProperties.fromUserPropertyCollection(userProperties);
+        }
+        if (propertyId == MqttPropertyType.SUBSCRIPTION_IDENTIFIER.value) {
+            List<IntegerProperty> subscriptionIds = this.subscriptionIds;
+            if (subscriptionIds == null || subscriptionIds.isEmpty()) {
+                return null;
+            }
+            return subscriptionIds.get(0);
+        }
+        IntObjectHashMap<MqttProperty> props = this.props;
+        return props == null ? null : props.get(propertyId);
+    }
+
+    /**
+     * Get properties by ID.
+     * Some properties (Subscription ID and User Properties) may occur multiple times,
+     * this method returns all their values in order.
+     *
+     * @param propertyId ID of the property
+     * @return all properties having specified ID
+     */
+    public List<? extends MqttProperty> getProperties(int propertyId) {
+        if (propertyId == MqttPropertyType.USER_PROPERTY.value) {
+            return userProperties == null ? Collections.<MqttProperty>emptyList() : userProperties;
+        }
+        if (propertyId == MqttPropertyType.SUBSCRIPTION_IDENTIFIER.value) {
+            return subscriptionIds == null ? Collections.<MqttProperty>emptyList() : subscriptionIds;
+        }
+        IntObjectHashMap<MqttProperty> props = this.props;
+        return (props == null || !props.containsKey(propertyId)) ?
+                Collections.<MqttProperty>emptyList() :
+                Collections.singletonList(props.get(propertyId));
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,7 +17,7 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#puback">MQTTV3.1/puback</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#puback">MQTTV3.1/puback</a>
 */
 public final class MqttPubAckMessage extends MqttMessage {

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.handler.codec.mqtt;
+
+import io.netty.util.internal.StringUtil;
+
+/**
+ * Variable Header containing Packet Id, reason code and Properties as in MQTT v5 spec.
+ */
+public final class MqttPubReplyMessageVariableHeader extends MqttMessageIdVariableHeader {
+
+    private final byte reasonCode;
+    private final MqttProperties properties;
+
+    public static final byte REASON_CODE_OK = 0;
+
+    public MqttPubReplyMessageVariableHeader(int messageId, byte reasonCode, MqttProperties properties) {
+        super(messageId);
+        if (messageId < 1 || messageId > 0xffff) {
+            throw new IllegalArgumentException("messageId: " + messageId + " (expected: 1 ~ 65535)");
+        }
+        this.reasonCode = reasonCode;
+        this.properties = MqttProperties.withEmptyDefaults(properties);
+    }
+
+    public byte reasonCode() {
+        return reasonCode;
+    }
+
+    public MqttProperties properties() {
+        return properties;
+    }
+
+    @Override
+    public String toString() {
+        return StringUtil.simpleClassName(this) + "[" +
+                "messageId=" + messageId() +
+                ", reasonCode=" + reasonCode +
+                ", properties=" + properties +
+                ']';
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -18,10 +18,10 @@ package io.netty.handler.codec.mqtt;

 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufHolder;
-import io.netty.util.IllegalReferenceCountException;
+import io.netty.buffer.ByteBufUtil;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#publish">MQTTV3.1/publish</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#publish">MQTTV3.1/publish</a>
 */
 public class MqttPublishMessage extends MqttMessage implements ByteBufHolder {

@@ -44,11 +44,7 @@ public class MqttPublishMessage extends MqttMessage implements ByteBufHolder {

    @Override
    public ByteBuf content() {
-        final ByteBuf data = (ByteBuf) super.payload();
-        if (data.refCnt() <= 0) {
-            throw new IllegalReferenceCountException(data.refCnt());
-        }
-        return data;
+        return ByteBufUtil.ensureAccessible((ByteBuf) super.payload());
    }

    @Override
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -24,11 +24,17 @@ import io.netty.util.internal.StringUtil;
 public final class MqttPublishVariableHeader {

    private final String topicName;
-    private final int packetId;
+    private int packetId;
+    private final MqttProperties properties;

    public MqttPublishVariableHeader(String topicName, int packetId) {
+        this(topicName, packetId, MqttProperties.NO_PROPERTIES);
+    }
+
+    public MqttPublishVariableHeader(String topicName, int packetId, MqttProperties properties) {
        this.topicName = topicName;
        this.packetId = packetId;
+        this.properties = MqttProperties.withEmptyDefaults(properties);
    }

    public String topicName() {
@@ -47,6 +53,14 @@ public final class MqttPublishVariableHeader {
        return packetId;
    }

+    public MqttProperties properties() {
+        return properties;
+    }
+
+    public void setPacketId(int packetId) {
+        this.packetId = packetId;
+    }
+
    @Override
    public String toString() {
        return new StringBuilder(StringUtil.simpleClassName(this))
@@ -5,7 +5,7 @@
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
- * http://www.apache.org/licenses/LICENSE-2.0
+ * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
@@ -32,11 +32,17 @@ public enum MqttQoS {
    }

    public static MqttQoS valueOf(int value) {
-        for (MqttQoS q: values()) {
-            if (q.value == value) {
-                return q;
-            }
+        switch (value) {
+        case 0:
+            return AT_MOST_ONCE;
+        case 1:
+            return AT_LEAST_ONCE;
+        case 2:
+            return EXACTLY_ONCE;
+        case 0x80:
+            return FAILURE;
+        default:
+            throw new IllegalArgumentException("invalid QoS: " + value);
        }
-        throw new IllegalArgumentException("invalid QoS: " + value);
    }
 }
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.handler.codec.mqtt;
+
+import io.netty.util.internal.StringUtil;
+
+/**
+ * Variable Header for AUTH and DISCONNECT messages represented by {@link MqttMessage}
+ */
+public final class MqttReasonCodeAndPropertiesVariableHeader {
+
+    private final byte reasonCode;
+    private final MqttProperties properties;
+
+    public static final byte REASON_CODE_OK = 0;
+
+    public MqttReasonCodeAndPropertiesVariableHeader(byte reasonCode,
+                                                     MqttProperties properties) {
+        this.reasonCode = reasonCode;
+        this.properties = MqttProperties.withEmptyDefaults(properties);
+    }
+
+    public byte reasonCode() {
+        return reasonCode;
+    }
+
+    public MqttProperties properties() {
+        return properties;
+    }
+
+    @Override
+    public String toString() {
+        return new StringBuilder(StringUtil.simpleClassName(this))
+            .append('[')
+            .append("reasonCode=").append(reasonCode)
+            .append(", properties=").append(properties)
+            .append(']')
+            .toString();
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,22 +17,33 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#suback">MQTTV3.1/suback</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#suback">MQTTV3.1/suback</a>
 */
 public final class MqttSubAckMessage extends MqttMessage {

    public MqttSubAckMessage(
            MqttFixedHeader mqttFixedHeader,
-            MqttMessageIdVariableHeader variableHeader,
+            MqttMessageIdAndPropertiesVariableHeader variableHeader,
            MqttSubAckPayload payload) {
        super(mqttFixedHeader, variableHeader, payload);
    }

+    public MqttSubAckMessage(
+            MqttFixedHeader mqttFixedHeader,
+            MqttMessageIdVariableHeader variableHeader,
+            MqttSubAckPayload payload) {
+        this(mqttFixedHeader, variableHeader.withDefaultEmptyProperties(), payload);
+    }
+
    @Override
    public MqttMessageIdVariableHeader variableHeader() {
        return (MqttMessageIdVariableHeader) super.variableHeader();
    }

+    public MqttMessageIdAndPropertiesVariableHeader idAndPropertiesVariableHeader() {
+        return (MqttMessageIdAndPropertiesVariableHeader) super.variableHeader();
+    }
+
    @Override
    public MqttSubAckPayload payload() {
        return (MqttSubAckPayload) super.payload();
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -16,6 +16,7 @@

 package io.netty.handler.codec.mqtt;

+import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.StringUtil;

 import java.util.ArrayList;
@@ -27,43 +28,51 @@ import java.util.List;
 */
 public class MqttSubAckPayload {

-    private final List<Integer> grantedQoSLevels;
+    private final List<Integer> reasonCodes;

-    public MqttSubAckPayload(int... grantedQoSLevels) {
-        if (grantedQoSLevels == null) {
-            throw new NullPointerException("grantedQoSLevels");
-        }
+    public MqttSubAckPayload(int... reasonCodes) {
+        ObjectUtil.checkNotNull(reasonCodes, "reasonCodes");

-        List<Integer> list = new ArrayList<Integer>(grantedQoSLevels.length);
-        for (int v: grantedQoSLevels) {
+        List<Integer> list = new ArrayList<Integer>(reasonCodes.length);
+        for (int v: reasonCodes) {
            list.add(v);
        }
-        this.grantedQoSLevels = Collections.unmodifiableList(list);
+        this.reasonCodes = Collections.unmodifiableList(list);
    }

-    public MqttSubAckPayload(Iterable<Integer> grantedQoSLevels) {
-        if (grantedQoSLevels == null) {
-            throw new NullPointerException("grantedQoSLevels");
-        }
+    public MqttSubAckPayload(Iterable<Integer> reasonCodes) {
+        ObjectUtil.checkNotNull(reasonCodes, "reasonCodes");
        List<Integer> list = new ArrayList<Integer>();
-        for (Integer v: grantedQoSLevels) {
+        for (Integer v: reasonCodes) {
            if (v == null) {
                break;
            }
            list.add(v);
        }
-        this.grantedQoSLevels = Collections.unmodifiableList(list);
+        this.reasonCodes = Collections.unmodifiableList(list);
    }

    public List<Integer> grantedQoSLevels() {
-        return grantedQoSLevels;
+        List<Integer> qosLevels = new ArrayList<Integer>(reasonCodes.size());
+        for (int code: reasonCodes) {
+            if (code > MqttQoS.EXACTLY_ONCE.value()) {
+                qosLevels.add(MqttQoS.FAILURE.value());
+            } else {
+                qosLevels.add(code);
+            }
+        }
+        return qosLevels;
+    }
+
+    public List<Integer> reasonCodes() {
+        return reasonCodes;
    }

    @Override
    public String toString() {
        return new StringBuilder(StringUtil.simpleClassName(this))
            .append('[')
-            .append("grantedQoSLevels=").append(grantedQoSLevels)
+            .append("reasonCodes=").append(reasonCodes)
            .append(']')
            .toString();
    }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,23 +17,34 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#subscribe">
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#subscribe">
 *     MQTTV3.1/subscribe</a>
 */
 public final class MqttSubscribeMessage extends MqttMessage {

    public MqttSubscribeMessage(
            MqttFixedHeader mqttFixedHeader,
-            MqttMessageIdVariableHeader variableHeader,
+            MqttMessageIdAndPropertiesVariableHeader variableHeader,
            MqttSubscribePayload payload) {
        super(mqttFixedHeader, variableHeader, payload);
    }

+    public MqttSubscribeMessage(
+            MqttFixedHeader mqttFixedHeader,
+            MqttMessageIdVariableHeader variableHeader,
+            MqttSubscribePayload payload) {
+        this(mqttFixedHeader, variableHeader.withDefaultEmptyProperties(), payload);
+    }
+
    @Override
    public MqttMessageIdVariableHeader variableHeader() {
        return (MqttMessageIdVariableHeader) super.variableHeader();
    }

+    public MqttMessageIdAndPropertiesVariableHeader idAndPropertiesVariableHeader() {
+        return (MqttMessageIdAndPropertiesVariableHeader) super.variableHeader();
+    }
+
    @Override
    public MqttSubscribePayload payload() {
        return (MqttSubscribePayload) super.payload();
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -39,11 +39,12 @@ public final class MqttSubscribePayload {
    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder(StringUtil.simpleClassName(this)).append('[');
-        for (int i = 0; i < topicSubscriptions.size() - 1; i++) {
+        for (int i = 0; i < topicSubscriptions.size(); i++) {
            builder.append(topicSubscriptions.get(i)).append(", ");
        }
-        builder.append(topicSubscriptions.get(topicSubscriptions.size() - 1));
-        builder.append(']');
-        return builder.toString();
+        if (!topicSubscriptions.isEmpty()) {
+            builder.setLength(builder.length() - 2);
+        }
+        return builder.append(']').toString();
    }
 }
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.mqtt;
+
+/**
+ * Model the SubscriptionOption used in Subscribe MQTT v5 packet
+ */
+public final class MqttSubscriptionOption {
+
+    public enum RetainedHandlingPolicy {
+        SEND_AT_SUBSCRIBE(0),
+        SEND_AT_SUBSCRIBE_IF_NOT_YET_EXISTS(1),
+        DONT_SEND_AT_SUBSCRIBE(2);
+
+        private final int value;
+
+        RetainedHandlingPolicy(int value) {
+            this.value = value;
+        }
+
+        public int value() {
+            return value;
+        }
+
+        public static RetainedHandlingPolicy valueOf(int value) {
+            switch (value) {
+            case 0:
+                return SEND_AT_SUBSCRIBE;
+            case 1:
+                return SEND_AT_SUBSCRIBE_IF_NOT_YET_EXISTS;
+            case 2:
+                return DONT_SEND_AT_SUBSCRIBE;
+            default:
+                throw new IllegalArgumentException("invalid RetainedHandlingPolicy: " + value);
+            }
+        }
+    }
+
+    private final MqttQoS qos;
+    private final boolean noLocal;
+    private final boolean retainAsPublished;
+    private final RetainedHandlingPolicy retainHandling;
+
+    public static MqttSubscriptionOption onlyFromQos(MqttQoS qos) {
+        return new MqttSubscriptionOption(qos, false, false, RetainedHandlingPolicy.SEND_AT_SUBSCRIBE);
+    }
+
+    public MqttSubscriptionOption(MqttQoS qos,
+                                  boolean noLocal,
+                                  boolean retainAsPublished,
+                                  RetainedHandlingPolicy retainHandling) {
+        this.qos = qos;
+        this.noLocal = noLocal;
+        this.retainAsPublished = retainAsPublished;
+        this.retainHandling = retainHandling;
+    }
+
+    public MqttQoS qos() {
+        return qos;
+    }
+
+    public boolean isNoLocal() {
+        return noLocal;
+    }
+
+    public boolean isRetainAsPublished() {
+        return retainAsPublished;
+    }
+
+    public RetainedHandlingPolicy retainHandling() {
+        return retainHandling;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        MqttSubscriptionOption that = (MqttSubscriptionOption) o;
+
+        if (noLocal != that.noLocal) {
+            return false;
+        }
+        if (retainAsPublished != that.retainAsPublished) {
+            return false;
+        }
+        if (qos != that.qos) {
+            return false;
+        }
+        return retainHandling == that.retainHandling;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = qos.hashCode();
+        result = 31 * result + (noLocal ? 1 : 0);
+        result = 31 * result + (retainAsPublished ? 1 : 0);
+        result = 31 * result + retainHandling.hashCode();
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "SubscriptionOption[" +
+                "qos=" + qos +
+                ", noLocal=" + noLocal +
+                ", retainAsPublished=" + retainAsPublished +
+                ", retainHandling=" + retainHandling +
+                ']';
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -25,11 +25,16 @@ import io.netty.util.internal.StringUtil;
 public final class MqttTopicSubscription {

    private final String topicFilter;
-    private final MqttQoS qualityOfService;
+    private final MqttSubscriptionOption option;

    public MqttTopicSubscription(String topicFilter, MqttQoS qualityOfService) {
        this.topicFilter = topicFilter;
-        this.qualityOfService = qualityOfService;
+        this.option = MqttSubscriptionOption.onlyFromQos(qualityOfService);
+    }
+
+    public MqttTopicSubscription(String topicFilter, MqttSubscriptionOption option) {
+        this.topicFilter = topicFilter;
+        this.option = option;
    }

    public String topicName() {
@@ -37,7 +42,11 @@ public final class MqttTopicSubscription {
    }

    public MqttQoS qualityOfService() {
-        return qualityOfService;
+        return option.qos();
+    }
+
+    public MqttSubscriptionOption option() {
+        return option;
    }

    @Override
@@ -45,7 +54,7 @@ public final class MqttTopicSubscription {
        return new StringBuilder(StringUtil.simpleClassName(this))
            .append('[')
            .append("topicFilter=").append(topicFilter)
-            .append(", qualityOfService=").append(qualityOfService)
+            .append(", option=").append(this.option)
            .append(']')
            .toString();
    }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,16 +17,46 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#unsuback">MQTTV3.1/unsuback</a>
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#unsuback">
+ *     MQTTV3.1/unsuback</a>
 */
 public final class MqttUnsubAckMessage extends MqttMessage {

-    public MqttUnsubAckMessage(MqttFixedHeader mqttFixedHeader, MqttMessageIdVariableHeader variableHeader) {
-        super(mqttFixedHeader, variableHeader, null);
+    public MqttUnsubAckMessage(MqttFixedHeader mqttFixedHeader,
+                               MqttMessageIdAndPropertiesVariableHeader variableHeader,
+                               MqttUnsubAckPayload payload) {
+        super(mqttFixedHeader, variableHeader, MqttUnsubAckPayload.withEmptyDefaults(payload));
+    }
+
+    public MqttUnsubAckMessage(MqttFixedHeader mqttFixedHeader,
+                               MqttMessageIdVariableHeader variableHeader,
+                               MqttUnsubAckPayload payload) {
+        this(mqttFixedHeader, fallbackVariableHeader(variableHeader), payload);
+    }
+    public MqttUnsubAckMessage(MqttFixedHeader mqttFixedHeader,
+                               MqttMessageIdVariableHeader variableHeader) {
+        this(mqttFixedHeader, variableHeader, null);
+    }
+
+    private static MqttMessageIdAndPropertiesVariableHeader fallbackVariableHeader(
+            MqttMessageIdVariableHeader variableHeader) {
+        if (variableHeader instanceof MqttMessageIdAndPropertiesVariableHeader) {
+            return (MqttMessageIdAndPropertiesVariableHeader) variableHeader;
+        }
+        return new MqttMessageIdAndPropertiesVariableHeader(variableHeader.messageId(), MqttProperties.NO_PROPERTIES);
    }

    @Override
    public MqttMessageIdVariableHeader variableHeader() {
        return (MqttMessageIdVariableHeader) super.variableHeader();
    }
+
+    public MqttMessageIdAndPropertiesVariableHeader idAndPropertiesVariableHeader() {
+        return (MqttMessageIdAndPropertiesVariableHeader) super.variableHeader();
+    }
+
+    @Override
+    public MqttUnsubAckPayload payload() {
+        return (MqttUnsubAckPayload) super.payload();
+    }
 }
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.mqtt;
+
+import io.netty.util.internal.ObjectUtil;
+import io.netty.util.internal.StringUtil;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Payload for MQTT unsuback message as in V5.
+ */
+public final class MqttUnsubAckPayload {
+
+    private final List<Short> unsubscribeReasonCodes;
+
+    private static final MqttUnsubAckPayload EMPTY = new MqttUnsubAckPayload();
+
+    public static MqttUnsubAckPayload withEmptyDefaults(MqttUnsubAckPayload payload) {
+        if (payload == null) {
+            return EMPTY;
+        } else {
+            return payload;
+        }
+    }
+
+    public MqttUnsubAckPayload(short... unsubscribeReasonCodes) {
+        ObjectUtil.checkNotNull(unsubscribeReasonCodes, "unsubscribeReasonCodes");
+
+        List<Short> list = new ArrayList<Short>(unsubscribeReasonCodes.length);
+        for (Short v: unsubscribeReasonCodes) {
+            list.add(v);
+        }
+        this.unsubscribeReasonCodes = Collections.unmodifiableList(list);
+    }
+
+    public MqttUnsubAckPayload(Iterable<Short> unsubscribeReasonCodes) {
+        ObjectUtil.checkNotNull(unsubscribeReasonCodes, "unsubscribeReasonCodes");
+
+        List<Short> list = new ArrayList<Short>();
+        for (Short v: unsubscribeReasonCodes) {
+            ObjectUtil.checkNotNull(v, "unsubscribeReasonCode");
+            list.add(v);
+        }
+        this.unsubscribeReasonCodes = Collections.unmodifiableList(list);
+    }
+
+    public List<Short> unsubscribeReasonCodes() {
+        return unsubscribeReasonCodes;
+    }
+
+    @Override
+    public String toString() {
+        return new StringBuilder(StringUtil.simpleClassName(this))
+                .append('[')
+                .append("unsubscribeReasonCodes=").append(unsubscribeReasonCodes)
+                .append(']')
+                .toString();
+    }
+}
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -17,23 +17,34 @@
 package io.netty.handler.codec.mqtt;

 /**
- * See <a href="http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#unsubscribe">
+ * See <a href="https://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html#unsubscribe">
 *     MQTTV3.1/unsubscribe</a>
 */
 public final class MqttUnsubscribeMessage extends MqttMessage {

    public MqttUnsubscribeMessage(
            MqttFixedHeader mqttFixedHeader,
-            MqttMessageIdVariableHeader variableHeader,
+            MqttMessageIdAndPropertiesVariableHeader variableHeader,
            MqttUnsubscribePayload payload) {
        super(mqttFixedHeader, variableHeader, payload);
    }

+    public MqttUnsubscribeMessage(
+            MqttFixedHeader mqttFixedHeader,
+            MqttMessageIdVariableHeader variableHeader,
+            MqttUnsubscribePayload payload) {
+        this(mqttFixedHeader, variableHeader.withDefaultEmptyProperties(), payload);
+    }
+
    @Override
    public MqttMessageIdVariableHeader variableHeader() {
        return (MqttMessageIdVariableHeader) super.variableHeader();
    }

+    public MqttMessageIdAndPropertiesVariableHeader idAndPropertiesVariableHeader() {
+        return (MqttMessageIdAndPropertiesVariableHeader) super.variableHeader();
+    }
+
    @Override
    public MqttUnsubscribePayload payload() {
        return (MqttUnsubscribePayload) super.payload();
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -39,11 +39,12 @@ public final class MqttUnsubscribePayload {
    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder(StringUtil.simpleClassName(this)).append('[');
-        for (int i = 0; i < topics.size() - 1; i++) {
+        for (int i = 0; i < topics.size(); i++) {
            builder.append("topicName = ").append(topics.get(i)).append(", ");
        }
-        builder.append("topicName = ").append(topics.get(topics.size() - 1))
-               .append(']');
-        return builder.toString();
+        if (!topics.isEmpty()) {
+            builder.setLength(builder.length() - 2);
+        }
+        return builder.append("]").toString();
    }
 }
@@ -5,7 +5,7 @@
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
@@ -25,7 +25,7 @@ import io.netty.util.internal.ObjectUtil;
 public enum MqttVersion {
    MQTT_3_1("MQIsdp", (byte) 3),
    MQTT_3_1_1("MQTT", (byte) 4),
-    Wildfire_1("MQTT", (byte) 5),
+    MQTT_5("MQTT", (byte) 5),
    Wildfire_2("MQTT", (byte) 6),
    Wildfire_Future("MQTT", (byte) 7);

@@ -50,21 +50,31 @@ public enum MqttVersion {
    }

    public static MqttVersion fromProtocolNameAndLevel(String protocolName, byte protocolLevel) {
-        for (MqttVersion mv : values()) {
-            if (mv.name.equals(protocolName)) {
-                if (mv.level == protocolLevel) {
-                    return mv;
-                } else {
-                    continue;
-                }
-            }
+        MqttVersion mv = null;
+        switch (protocolLevel) {
+        case 3:
+            mv = MQTT_3_1;
+            break;
+        case 4:
+            mv = MQTT_3_1_1;
+            break;
+        case 5:
+            mv = MQTT_5;
+            break;
+        case 6:
+            mv = Wildfire_2;
+            break;
+        case 7:
+            mv = Wildfire_Future;
+            break;
+        default:
+            mv = Wildfire_Future;
+            break;
        }
-        if(protocolLevel > Wildfire_Future.level) {
-            return Wildfire_Future;
-        }
-        throw new MqttUnacceptableProtocolVersionException(protocolName + "is unknown protocol name");
-    }

+        return mv;
+    }
+    
    public static MqttVersion fromProtocolLevel(int protocolLevel) {
        for (MqttVersion mv : values()) {
            if (mv.level == (byte )protocolLevel) {
@@ -5,7 +5,7 @@
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
- * http://www.apache.org/licenses/LICENSE-2.0
+ * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
@@ -3,7 +3,7 @@
    <modelVersion>4.0.0</modelVersion>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <netty.version>4.1.12.Final</netty.version>
+        <netty.version>4.1.68.Final</netty.version>
        <source.version>1.8</source.version>
        <target.version>1.8</target.version>
    </properties>