增加协议版本，新版本添加对gzip的支持

broker/src/main/java/io/netty/handler/codec/mqtt/MqttCodecUtil.java

@@ -43,7 +43,7 @@ final class MqttCodecUtil {
             return clientId != null && clientId.length() >= MIN_CLIENT_ID_LENGTH &&
                 clientId.length() <= MAX_CLIENT_ID_LENGTH;
         }
-        if (mqttVersion == MqttVersion.MQTT_3_1_1) {
+        if (mqttVersion == MqttVersion.MQTT_3_1_1 || mqttVersion == MqttVersion.Wildfire_1) {
             // In 3.1.3.1 Client Identifier of MQTT 3.1.1 specification, The Server MAY allow ClientId’s
             // that contain more than 23 encoded bytes. And, The Server MAY allow zero-length ClientId.
             return clientId != null;

broker/src/main/java/io/netty/handler/codec/mqtt/MqttDecoder.java

@@ -223,7 +223,7 @@ 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 == MqttVersion.MQTT_3_1_1) {
+        if (mqttVersion == MqttVersion.MQTT_3_1_1 || mqttVersion == MqttVersion.Wildfire_1) {
             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

broker/src/main/java/io/netty/handler/codec/mqtt/MqttVersion.java

@@ -24,7 +24,8 @@ import io.netty.util.internal.ObjectUtil;
  */
 public enum MqttVersion {
     MQTT_3_1("MQIsdp", (byte) 3),
-    MQTT_3_1_1("MQTT", (byte) 4);
+    MQTT_3_1_1("MQTT", (byte) 4),
+    Wildfire_1("MQTT", (byte) 5);
 
     private final String name;
     private final byte level;
@@ -52,11 +53,19 @@ public enum MqttVersion {
                 if (mv.level == protocolLevel) {
                     return mv;
                 } else {
-                    throw new MqttUnacceptableProtocolVersionException(protocolName + " and " +
-                            protocolLevel + " are not match");
+                    continue;
                 }
             }
         }
         throw new MqttUnacceptableProtocolVersionException(protocolName + "is unknown protocol name");
     }
+
+    public static MqttVersion fromProtocolLevel(int protocolLevel) {
+        for (MqttVersion mv : values()) {
+            if (mv.level == (byte )protocolLevel) {
+                return mv;
+            }
+        }
+        throw new MqttUnacceptableProtocolVersionException(protocolLevel + "is unknown protocol level");
+    }
 }