Fix serialization issue of MQTTv5 PubRec packet.

Source/MQTTnet/Formatter/IMqttPacketWriter.cs

@@ -5,15 +5,25 @@
         int Length { get; }
 
         void WriteWithLengthPrefix(string value);
-        void Write(byte returnCode);
-        void WriteWithLengthPrefix(byte[] payload);
-        void Write(ushort keepAlivePeriod);
-        void Write(IMqttPacketWriter propertyWriter);
-        void WriteVariableLengthInteger(uint length);
-        void Write(byte[] payload, int v, int length);
-        void Reset(int v);
-        void Seek(int v);
+
+        void Write(byte value);
+
+        void WriteWithLengthPrefix(byte[] value);
+
+        void Write(ushort value);
+
+        void Write(IMqttPacketWriter value);
+
+        void WriteVariableLengthInteger(uint value);
+
+        void Write(byte[] value, int offset, int length);
+
+        void Reset(int length);
+
+        void Seek(int offset);
+
         void FreeBuffer();
+
         byte[] GetBuffer();
     }
 }

Source/MQTTnet/Formatter/V5/MqttV500PacketEncoder.cs

@@ -328,10 +328,7 @@ namespace MQTTnet.Formatter.V5
             {
                 ThrowReasonCodeNotSetException();
             }
-
-            packetWriter.Write(packet.PacketIdentifier.Value);
-            packetWriter.Write((byte)packet.ReasonCode.Value);
-
+           
             var propertiesWriter = new MqttV500PropertiesWriter();
             if (packet.Properties != null)
             {
@@ -339,6 +336,8 @@ namespace MQTTnet.Formatter.V5
                 propertiesWriter.WriteUserProperties(packet.Properties.UserProperties);
             }
 
+            packetWriter.Write(packet.PacketIdentifier.Value);
+
             if (packetWriter.Length > 0 || packet.ReasonCode.Value != MqttPubRecReasonCode.Success)
             {
                 packetWriter.Write((byte)packet.ReasonCode.Value);