Add serializer adapter.

Source/MQTTnet.AspnetCore/Client/MqttClientConnectionContextFactory.cs

@@ -14,15 +14,13 @@ namespace MQTTnet.AspNetCore.Client
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            var serializer = new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion };
-
             switch (options.ChannelOptions)
             {
                 case MqttClientTcpOptions tcpOptions:
                     {
                         var endpoint = new DnsEndPoint(tcpOptions.Server, tcpOptions.GetPort());
                         var tcpConnection = new TcpConnection(endpoint);
-                        return new MqttConnectionContext(serializer, tcpConnection);
+                        return new MqttConnectionContext(new MqttPacketSerializerAdapter(options.ProtocolVersion), tcpConnection);
                     }
                 default:
                     {

Source/MQTTnet.AspnetCore/MqttConnectionContext.cs

@@ -12,17 +12,15 @@ namespace MQTTnet.AspNetCore
 {
     public class MqttConnectionContext : IMqttChannelAdapter
     {
-        public MqttConnectionContext(
-            IMqttPacketSerializer packetSerializer,
-            ConnectionContext connection)
+        public MqttConnectionContext(MqttPacketSerializerAdapter packetSerializerAdapter, ConnectionContext connection)
         {
-            PacketSerializer = packetSerializer;
-            Connection = connection;
+            PacketSerializerAdapter = packetSerializerAdapter ?? throw new ArgumentNullException(nameof(packetSerializerAdapter));
+            Connection = connection ?? throw new ArgumentNullException(nameof(connection));
         }
 
         public string Endpoint => Connection.ConnectionId;
         public ConnectionContext Connection { get; }
-        public IMqttPacketSerializer PacketSerializer { get; }
+        public MqttPacketSerializerAdapter PacketSerializerAdapter { get; }
         public event EventHandler ReadingPacketStarted;
         public event EventHandler ReadingPacketCompleted;
 
@@ -71,7 +69,7 @@ namespace MQTTnet.AspNetCore
                     {
                         if (!buffer.IsEmpty)
                         {
-                            if (PacketSerializer.TryDeserialize(buffer, out var packet, out consumed, out observed))
+                            if (PacketSerializerAdapter.Serializer.TryDeserialize(buffer, out var packet, out consumed, out observed))
                             {
                                 return packet;
                             }
@@ -106,7 +104,7 @@ namespace MQTTnet.AspNetCore
 
         public Task SendPacketAsync(MqttBasePacket packet, CancellationToken cancellationToken)
         {
-            var buffer = PacketSerializer.Serialize(packet);
+            var buffer = PacketSerializerAdapter.Serialize(packet);
             return Connection.Transport.Output.WriteAsync(buffer.AsMemory(), cancellationToken).AsTask();
         }
 

Source/MQTTnet.AspnetCore/MqttConnectionHandler.cs

@@ -9,7 +9,7 @@ using System.Threading.Tasks;
 namespace MQTTnet.AspNetCore
 {
     public class MqttConnectionHandler : ConnectionHandler, IMqttServerAdapter
-    {        
+    {
         public event EventHandler<MqttServerAdapterClientAcceptedEventArgs> ClientAccepted;
 
         public override async Task OnConnectedAsync(ConnectionContext connection)
@@ -21,9 +21,7 @@ namespace MQTTnet.AspNetCore
                 transferFormatFeature.ActiveFormat = TransferFormat.Binary;
             }
 
-
-            var serializer = new MqttPacketSerializer();
-            using (var adapter = new MqttConnectionContext(serializer, connection))
+            using (var adapter = new MqttConnectionContext(new MqttPacketSerializerAdapter(), connection))
             {
                 var args = new MqttServerAdapterClientAcceptedEventArgs(adapter);
                 ClientAccepted?.Invoke(this, args);
@@ -41,7 +39,7 @@ namespace MQTTnet.AspNetCore
         {
             return Task.CompletedTask;
         }
-        
+
         public void Dispose()
         {
         }

Source/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -27,7 +27,7 @@ namespace MQTTnet.AspNetCore
         {
             if (webSocket == null) throw new ArgumentNullException(nameof(webSocket));
 
-            var clientAdapter = new MqttChannelAdapter(new MqttWebSocketChannel(webSocket, endpoint), new MqttPacketSerializer(), new MqttNetLogger().CreateChildLogger(nameof(MqttWebSocketServerAdapter)));
+            var clientAdapter = new MqttChannelAdapter(new MqttWebSocketChannel(webSocket, endpoint), new MqttPacketSerializerAdapter(), new MqttNetLogger().CreateChildLogger(nameof(MqttWebSocketServerAdapter)));
 
             var eventArgs = new MqttServerAdapterClientAcceptedEventArgs(clientAdapter);
             ClientAccepted?.Invoke(this, eventArgs);
@@ -37,7 +37,7 @@ namespace MQTTnet.AspNetCore
                 await eventArgs.SessionTask.ConfigureAwait(false);
             }
         }
-        
+
         public void Dispose()
         {
             StopAsync().GetAwaiter().GetResult();

Source/MQTTnet/Adapter/IMqttChannelAdapter.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Adapter
     {
         string Endpoint { get; }
 
-        IMqttPacketSerializer PacketSerializer { get; }
+        MqttPacketSerializerAdapter PacketSerializerAdapter { get; }
 
         event EventHandler ReadingPacketStarted;
 

Source/MQTTnet/Adapter/MqttChannelAdapter.cs

@@ -22,26 +22,25 @@ namespace MQTTnet.Adapter
 
         private readonly IMqttNetChildLogger _logger;
         private readonly IMqttChannel _channel;
-
+        
         private readonly byte[] _fixedHeaderBuffer = new byte[2];
-
         private readonly byte[] _singleByteBuffer = new byte[1];
 
         private bool _isDisposed;
 
-        public MqttChannelAdapter(IMqttChannel channel, IMqttPacketSerializer serializer, IMqttNetChildLogger logger)
+        public MqttChannelAdapter(IMqttChannel channel, MqttPacketSerializerAdapter packetSerializerAdapter, IMqttNetChildLogger logger)
         {
             if (logger == null) throw new ArgumentNullException(nameof(logger));
 
             _channel = channel ?? throw new ArgumentNullException(nameof(channel));
-            PacketSerializer = serializer ?? throw new ArgumentNullException(nameof(serializer));
-
+            PacketSerializerAdapter = packetSerializerAdapter ?? throw new ArgumentNullException(nameof(packetSerializerAdapter));
+            
             _logger = logger.CreateChildLogger(nameof(MqttChannelAdapter));
         }
 
         public string Endpoint => _channel.Endpoint;
 
-        public IMqttPacketSerializer PacketSerializer { get; }
+        public MqttPacketSerializerAdapter PacketSerializerAdapter { get; }
 
         public event EventHandler ReadingPacketStarted;
         public event EventHandler ReadingPacketCompleted;
@@ -91,15 +90,15 @@ namespace MQTTnet.Adapter
                 WrapException(exception);
             }
         }
-
+        
         public async Task SendPacketAsync(MqttBasePacket packet, CancellationToken cancellationToken)
         {
             await _writerSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
             try
             {
-                var packetData = PacketSerializer.Serialize(packet);
+                var packetData = PacketSerializerAdapter.Serialize(packet);
                 await _channel.WriteAsync(packetData.Array, packetData.Offset, packetData.Count, cancellationToken).ConfigureAwait(false);
-                PacketSerializer.FreeBuffer();
+                PacketSerializerAdapter.FreeBuffer();
 
                 _logger.Verbose("TX >>> {0}", packet);
             }
@@ -140,7 +139,12 @@ namespace MQTTnet.Adapter
                     return null;
                 }
 
-                var packet = PacketSerializer.Deserialize(receivedMqttPacket);
+                if (!PacketSerializerAdapter.ProtocolVersion.HasValue)
+                {
+                    PacketSerializerAdapter.DetectProtocolVersion(receivedMqttPacket);
+                }
+
+                var packet = PacketSerializerAdapter.Deserialize(receivedMqttPacket);
                 if (packet == null)
                 {
                     throw new MqttProtocolViolationException("Received malformed packet.");

Source/MQTTnet/Client/MqttClient.cs

@@ -9,6 +9,7 @@ using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
 using MQTTnet.Internal;
 using MQTTnet.Packets;
+using MQTTnet.Packets.V3;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Client
@@ -61,7 +62,7 @@ namespace MQTTnet.Client
                 _packetDispatcher.Reset();
 
                 _adapter = _adapterFactory.CreateClientAdapter(options, _logger);
-
+                
                 _logger.Verbose($"Trying to connect with server ({_options.ChannelOptions}).");
                 await _adapter.ConnectAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token).ConfigureAwait(false);
                 _logger.Verbose("Connection with server established.");
@@ -189,9 +190,9 @@ namespace MQTTnet.Client
             _adapter?.Dispose();
         }
 
-        private async Task<MqttConnAckPacket> AuthenticateAsync(MqttApplicationMessage willApplicationMessage, CancellationToken cancellationToken)
+        private async Task<MqttV3ConnAckPacket> AuthenticateAsync(MqttApplicationMessage willApplicationMessage, CancellationToken cancellationToken)
         {
-            var connectPacket = new MqttConnectPacket
+            var connectPacket = new MqttV3ConnectPacket
             {
                 ClientId = _options.ClientId,
                 Username = _options.Credentials?.Username,
@@ -201,7 +202,7 @@ namespace MQTTnet.Client
                 WillMessage = willApplicationMessage
             };
 
-            var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket, cancellationToken).ConfigureAwait(false);
+            var response = await SendAndReceiveAsync<MqttV3ConnAckPacket>(connectPacket, cancellationToken).ConfigureAwait(false);
             if (response.ConnectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
             {
                 throw new MqttConnectingFailedException(response.ConnectReturnCode);

Source/MQTTnet/Implementations/MqttClientAdapterFactory.cs

@@ -11,19 +11,17 @@ namespace MQTTnet.Implementations
         public IMqttChannelAdapter CreateClientAdapter(IMqttClientOptions options, IMqttNetChildLogger logger)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
-
-            var serializer = new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion };
-
+            
             switch (options.ChannelOptions)
             {
                 case MqttClientTcpOptions _:
                     {
-                        return new MqttChannelAdapter(new MqttTcpChannel(options), serializer, logger);
+                        return new MqttChannelAdapter(new MqttTcpChannel(options), new MqttPacketSerializerAdapter(options.ProtocolVersion), logger);
                     }
 
                 case MqttClientWebSocketOptions webSocketOptions:
                     {
-                        return new MqttChannelAdapter(new MqttWebSocketChannel(webSocketOptions), serializer, logger);
+                        return new MqttChannelAdapter(new MqttWebSocketChannel(webSocketOptions), new MqttPacketSerializerAdapter(options.ProtocolVersion), logger);
                     }
 
                 default:

Source/MQTTnet/Implementations/MqttTcpServerAdapter.Uwp.cs

@@ -72,7 +72,7 @@ namespace MQTTnet.Implementations
         {
             try
             {
-                var clientAdapter = new MqttChannelAdapter(new MqttTcpChannel(args.Socket, _options), new MqttPacketSerializer(), _logger);
+                var clientAdapter = new MqttChannelAdapter(new MqttTcpChannel(args.Socket, _options), new MqttPacketSerializerAdapter(), _logger);
                 ClientAccepted?.Invoke(this, new MqttServerAdapterClientAcceptedEventArgs(clientAdapter));
             }
             catch (Exception exception)

Source/MQTTnet/Implementations/MqttTcpServerListener.cs

@@ -83,7 +83,7 @@ namespace MQTTnet.Implementations
                         _socket.LocalEndPoint,
                         _addressFamily == AddressFamily.InterNetwork ? "ipv4" : "ipv6");
 
-                    var clientAdapter = new MqttChannelAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttPacketSerializer(), _logger);
+                    var clientAdapter = new MqttChannelAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttPacketSerializerAdapter(), _logger);
                     ClientAccepted?.Invoke(this, new MqttServerAdapterClientAcceptedEventArgs(clientAdapter));
                 }
                 catch (ObjectDisposedException)

Source/MQTTnet/MQTTnet.csproj

@@ -63,4 +63,8 @@
   <ItemGroup Condition="'$(TargetFramework)'=='net461'">
   </ItemGroup>
 
+  <ItemGroup>
+    <Folder Include="Packets\V5\" />
+  </ItemGroup>
+
 </Project>

Source/MQTTnet/Packets/MqttConnAckPacket.cs

@@ -1,16 +1,6 @@
-using MQTTnet.Protocol;
-
-namespace MQTTnet.Packets
+namespace MQTTnet.Packets
 {
-    public class MqttConnAckPacket : MqttBasePacket
+    public abstract class MqttConnAckPacket : MqttBasePacket
     {
-        public bool IsSessionPresent { get; set; }
-
-        public MqttConnectReturnCode ConnectReturnCode { get; set; }
-
-        public override string ToString()
-        {
-            return "ConnAck: [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
-        }
     }
 }

Source/MQTTnet/Packets/MqttConnectPacket.cs

@@ -1,26 +1,6 @@
-using MQTTnet.Serializer;
-
-namespace MQTTnet.Packets
+namespace MQTTnet.Packets
 {
-    public class MqttConnectPacket : MqttBasePacket
+    public abstract class MqttConnectPacket : MqttBasePacket
     {
-        public MqttProtocolVersion ProtocolVersion { get; set; }
-
-        public string ClientId { get; set; }
-
-        public string Username { get; set; }
-
-        public string Password { get; set; }
-
-        public ushort KeepAlivePeriod { get; set; }
-
-        public bool CleanSession { get; set; }
-
-        public MqttApplicationMessage WillMessage { get; set; }
-
-        public override string ToString()
-        {
-            return "Connect: [ClientId=" + ClientId + "] [Username=" + Username + "] [Password=" + Password + "] [KeepAlivePeriod=" + KeepAlivePeriod + "] [CleanSession=" + CleanSession + "]";
-        }
     }
 }

Source/MQTTnet/Packets/V3/MqttV3ConnAckPacket.cs

@@ -0,0 +1,16 @@
+using MQTTnet.Protocol;
+
+namespace MQTTnet.Packets.V3
+{
+    public class MqttV3ConnAckPacket : MqttBasePacket
+    {
+        public bool IsSessionPresent { get; set; }
+
+        public MqttConnectReturnCode ConnectReturnCode { get; set; }
+
+        public override string ToString()
+        {
+            return "ConnAck: [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
+        }
+    }
+}

Source/MQTTnet/Packets/V3/MqttV3ConnectPacket.cs

@@ -0,0 +1,26 @@
+namespace MQTTnet.Packets.V3
+{
+    public class MqttV3ConnectPacket : MqttConnectPacket
+    {
+        public string ProtocolName { get; set; }
+
+        public byte ProtocolLevel { get; set; }
+
+        public string ClientId { get; set; }
+
+        public string Username { get; set; }
+
+        public string Password { get; set; }
+
+        public ushort KeepAlivePeriod { get; set; }
+
+        public bool CleanSession { get; set; }
+
+        public MqttApplicationMessage WillMessage { get; set; }
+
+        public override string ToString()
+        {
+            return "Connect: [ProtocolLevel=" + ProtocolLevel + "] [ClientId=" + ClientId + "] [Username=" + Username + "] [Password=" + Password + "] [KeepAlivePeriod=" + KeepAlivePeriod + "] [CleanSession=" + CleanSession + "]";
+        }
+    }
+}

Source/MQTTnet/Serializer/IMqttPacketSerializer.cs

@@ -6,8 +6,6 @@ namespace MQTTnet.Serializer
 {
     public interface IMqttPacketSerializer
     {
-        MqttProtocolVersion ProtocolVersion { get; set; }
-
         ArraySegment<byte> Serialize(MqttBasePacket mqttPacket);
 
         MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket);

Source/MQTTnet/Serializer/MqttPacketBodyReader.cs

@@ -6,6 +6,7 @@ namespace MQTTnet.Serializer
     public class MqttPacketBodyReader
     {
         private readonly byte[] _buffer;
+        private readonly int _initialOffset;
         private readonly int _length;
 
         private int _offset;
@@ -13,6 +14,7 @@ namespace MQTTnet.Serializer
         public MqttPacketBodyReader(byte[] buffer, int offset, int length)
         {
             _buffer = buffer;
+            _initialOffset = offset;
             _offset = offset;
             _length = length;
         }
@@ -21,6 +23,11 @@ namespace MQTTnet.Serializer
 
         public bool EndOfStream => _offset == _length;
 
+        public void Seek(int position)
+        {
+            _offset = _initialOffset + position;
+        }
+
         public byte ReadByte()
         {
             ValidateReceiveBuffer(1);

Source/MQTTnet/Serializer/MqttPacketSerializerAdapter.cs

@@ -0,0 +1,123 @@
+using System;
+using MQTTnet.Adapter;
+using MQTTnet.Exceptions;
+using MQTTnet.Packets;
+
+namespace MQTTnet.Serializer
+{
+    public class MqttPacketSerializerAdapter
+    {
+        public MqttPacketSerializerAdapter()
+        {
+        }
+
+        public MqttPacketSerializerAdapter(MqttProtocolVersion protocolVersion)
+        {
+            UseProtocolVersion(protocolVersion);
+        }
+
+        public MqttProtocolVersion? ProtocolVersion { get; private set; }
+
+        public IMqttPacketSerializer Serializer { get; private set; }
+
+        public ArraySegment<byte> Serialize(MqttBasePacket packet)
+        {
+            if (Serializer == null)
+            {
+                throw new InvalidOperationException("Protocol version not set or detected.");
+            }
+
+            return Serializer.Serialize(packet);
+        }
+
+        public MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket)
+        {
+            if (Serializer == null)
+            {
+                throw new InvalidOperationException("Protocol version nor set or detected.");
+            }
+
+            return Serializer.Deserialize(receivedMqttPacket);
+        }
+
+        public void FreeBuffer()
+        {
+            Serializer?.FreeBuffer();
+        }
+
+        public void DetectProtocolVersion(ReceivedMqttPacket receivedMqttPacket)
+        {
+            var protocolVersion = ParseProtocolVersion(receivedMqttPacket);
+            receivedMqttPacket.Body.Seek(0);
+
+            UseProtocolVersion(protocolVersion);
+        }
+
+        private void UseProtocolVersion(MqttProtocolVersion protocolVersion)
+        {
+            ProtocolVersion = protocolVersion;
+
+            switch (protocolVersion)
+            {
+                case MqttProtocolVersion.V500:
+                    {
+                        Serializer = new MqttV500PacketSerializer();
+                        break;
+                    }
+
+                case MqttProtocolVersion.V311:
+                    {
+                        Serializer = new MqttV311PacketSerializer();
+                        break;
+                    }
+
+                case MqttProtocolVersion.V310:
+                    {
+
+                        Serializer = new MqttV310PacketSerializer();
+                        break;
+                    }
+                    
+                default:
+                    {
+                        throw new NotSupportedException();
+                    }
+            }
+        }
+
+        private MqttProtocolVersion ParseProtocolVersion(ReceivedMqttPacket receivedMqttPacket)
+        {
+            if (receivedMqttPacket == null) throw new ArgumentNullException(nameof(receivedMqttPacket));
+
+            var protocolName = receivedMqttPacket.Body.ReadStringWithLengthPrefix();
+            var protocolLevel = receivedMqttPacket.Body.ReadByte();
+
+            if (protocolName == "MQTT")
+            {
+                if (protocolLevel == 5)
+                {
+                    return MqttProtocolVersion.V500;
+                }
+
+                if (protocolLevel == 4)
+                {
+                    return MqttProtocolVersion.V311;
+                }
+
+                throw new MqttProtocolViolationException($"Protocol level '{protocolLevel}' not supported.");
+            }
+
+            if (protocolName == "MQIsdp")
+            {
+                if (protocolLevel == 3)
+                {
+                    return MqttProtocolVersion.V310;
+                }
+
+                throw new MqttProtocolViolationException($"Protocol level '{protocolLevel}' not supported.");
+            }
+
+            throw new MqttProtocolViolationException($"Protocol '{protocolName}' not supported.");
+        }
+    }
+}

Source/MQTTnet/Serializer/MqttPacketWriter.cs

@@ -100,10 +100,10 @@ namespace MQTTnet.Serializer
             Length = 5;
         }
 
-        public void Seek(int offset)
+        public void Seek(int position)
         {
-            EnsureCapacity(offset);
-            _position = offset;
+            EnsureCapacity(position);
+            _position = position;
         }
 
         public byte[] GetBuffer()

Source/MQTTnet/Serializer/MqttProtocolVersion.cs

@@ -2,7 +2,8 @@
 {
     public enum MqttProtocolVersion
     {
-        V311,
-        V310
+        V310 = 3,
+        V311 = 4,
+        V500 = 5
     }
 }

Source/MQTTnet/Serializer/MqttV310PacketSerializer.cs

@@ -4,17 +4,16 @@ using MQTTnet.Protocol;
 using System;
 using System.Linq;
 using MQTTnet.Adapter;
+using MQTTnet.Packets.V3;
 
 namespace MQTTnet.Serializer
 {
-    public class MqttPacketSerializer : IMqttPacketSerializer
+    public class MqttV310PacketSerializer : IMqttPacketSerializer
     {
         private const int FixedHeaderSize = 1;
 
         private readonly MqttPacketWriter _packetWriter = new MqttPacketWriter();
 
-        public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
-
         public ArraySegment<byte> Serialize(MqttBasePacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
@@ -52,8 +51,8 @@ namespace MQTTnet.Serializer
 
             switch ((MqttControlPacketType)controlPacketType)
             {
-                case MqttControlPacketType.Connect: return DeserializeConnect(receivedMqttPacket.Body);
-                case MqttControlPacketType.ConnAck: return DeserializeConnAck(receivedMqttPacket.Body);
+                case MqttControlPacketType.Connect: return DeserializeConnectPacket(receivedMqttPacket.Body);
+                case MqttControlPacketType.ConnAck: return DeserializeConnAckPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.Disconnect: return new MqttDisconnectPacket();
                 case MqttControlPacketType.Publish: return DeserializePublish(receivedMqttPacket);
                 case MqttControlPacketType.PubAck: return DeserializePubAck(receivedMqttPacket.Body);
@@ -63,7 +62,7 @@ namespace MQTTnet.Serializer
                 case MqttControlPacketType.PingReq: return new MqttPingReqPacket();
                 case MqttControlPacketType.PingResp: return new MqttPingRespPacket();
                 case MqttControlPacketType.Subscribe: return DeserializeSubscribe(receivedMqttPacket.Body);
-                case MqttControlPacketType.SubAck: return DeserializeSubAck(receivedMqttPacket.Body);
+                case MqttControlPacketType.SubAck: return DeserializeSubAckPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.Unsubscibe: return DeserializeUnsubscribe(receivedMqttPacket.Body);
                 case MqttControlPacketType.UnsubAck: return DeserializeUnsubAck(receivedMqttPacket.Body);
 
@@ -80,20 +79,20 @@ namespace MQTTnet.Serializer
         {
             switch (packet)
             {
-                case MqttConnectPacket connectPacket: return Serialize(connectPacket, packetWriter);
-                case MqttConnAckPacket connAckPacket: return Serialize(connAckPacket, packetWriter);
+                case MqttV3ConnectPacket connectPacket: return SerializeConnectPacket(connectPacket, packetWriter);
+                case MqttV3ConnAckPacket connAckPacket: return SerializeConnAckPacket(connAckPacket, packetWriter);
                 case MqttDisconnectPacket _: return SerializeEmptyPacket(MqttControlPacketType.Disconnect);
                 case MqttPingReqPacket _: return SerializeEmptyPacket(MqttControlPacketType.PingReq);
                 case MqttPingRespPacket _: return SerializeEmptyPacket(MqttControlPacketType.PingResp);
-                case MqttPublishPacket publishPacket: return Serialize(publishPacket, packetWriter);
-                case MqttPubAckPacket pubAckPacket: return Serialize(pubAckPacket, packetWriter);
-                case MqttPubRecPacket pubRecPacket: return Serialize(pubRecPacket, packetWriter);
-                case MqttPubRelPacket pubRelPacket: return Serialize(pubRelPacket, packetWriter);
-                case MqttPubCompPacket pubCompPacket: return Serialize(pubCompPacket, packetWriter);
-                case MqttSubscribePacket subscribePacket: return Serialize(subscribePacket, packetWriter);
-                case MqttSubAckPacket subAckPacket: return Serialize(subAckPacket, packetWriter);
-                case MqttUnsubscribePacket unsubscribePacket: return Serialize(unsubscribePacket, packetWriter);
-                case MqttUnsubAckPacket unsubAckPacket: return Serialize(unsubAckPacket, packetWriter);
+                case MqttPublishPacket publishPacket: return SerializePublishPacket(publishPacket, packetWriter);
+                case MqttPubAckPacket pubAckPacket: return SerializePubAckPacket(pubAckPacket, packetWriter);
+                case MqttPubRecPacket pubRecPacket: return SerializePubRecPacket(pubRecPacket, packetWriter);
+                case MqttPubRelPacket pubRelPacket: return SerializePubRelPacket(pubRelPacket, packetWriter);
+                case MqttPubCompPacket pubCompPacket: return SerializePubCompPacket(pubCompPacket, packetWriter);
+                case MqttSubscribePacket subscribePacket: return SerializeSubscribePacket(subscribePacket, packetWriter);
+                case MqttSubAckPacket subAckPacket: return SerializeSubAckPacket(subAckPacket, packetWriter);
+                case MqttUnsubscribePacket unsubscribePacket: return SerializeUnsubscribePacket(unsubscribePacket, packetWriter);
+                case MqttUnsubAckPacket unsubAckPacket: return SerializeUnsubAckPacket(unsubAckPacket, packetWriter);
                 default: throw new MqttProtocolViolationException("Packet type invalid.");
             }
         }
@@ -213,49 +212,23 @@ namespace MQTTnet.Serializer
             return packet;
         }
 
-        private static MqttBasePacket DeserializeConnect(MqttPacketBodyReader body)
+        private MqttBasePacket DeserializeConnectPacket(MqttPacketBodyReader body)
         {
             ThrowIfBodyIsEmpty(body);
 
-            var protocolName = body.ReadStringWithLengthPrefix();
-
-            MqttProtocolVersion protocolVersion;
-            if (protocolName == "MQTT")
+            var packet = new MqttV3ConnectPacket
             {
-                var protocolLevel = body.ReadByte();
-                if (protocolLevel != 4)
-                {
-                    throw new MqttProtocolViolationException($"Protocol level ({protocolLevel}) not supported for MQTT 3.1.1.");
-                }
-
-                protocolVersion = MqttProtocolVersion.V311;
-            }
-            else if (protocolName == "MQIsdp")
-            {
-                var protocolLevel = body.ReadByte();
-                if (protocolLevel != 3)
-                {
-                    throw new MqttProtocolViolationException($"Protocol level ({protocolLevel}) not supported for MQTT 3.1.");
-                }
-
-                protocolVersion = MqttProtocolVersion.V310;
-            }
-            else
-            {
-                throw new MqttProtocolViolationException($"Protocol name ({protocolName}) is not supported.");
-            }
-
+                ProtocolName = body.ReadStringWithLengthPrefix(),
+                ProtocolLevel = body.ReadByte()
+            };
+            
             var connectFlags = body.ReadByte();
             if ((connectFlags & 0x1) > 0)
             {
                 throw new MqttProtocolViolationException("The first bit of the Connect Flags must be set to 0.");
             }
 
-            var packet = new MqttConnectPacket
-            {
-                ProtocolVersion = protocolVersion,
-                CleanSession = (connectFlags & 0x2) > 0
-            };
+            packet.CleanSession = (connectFlags & 0x2) > 0;
 
             var willFlag = (connectFlags & 0x4) > 0;
             var willQoS = (connectFlags & 0x18) >> 3;
@@ -291,7 +264,7 @@ namespace MQTTnet.Serializer
             return packet;
         }
 
-        private static MqttBasePacket DeserializeSubAck(MqttPacketBodyReader body)
+        private static MqttBasePacket DeserializeSubAckPacket(MqttPacketBodyReader body)
         {
             ThrowIfBodyIsEmpty(body);
 
@@ -308,25 +281,19 @@ namespace MQTTnet.Serializer
             return packet;
         }
 
-        private MqttBasePacket DeserializeConnAck(MqttPacketBodyReader body)
+        protected virtual MqttBasePacket DeserializeConnAckPacket(MqttPacketBodyReader body)
         {
             ThrowIfBodyIsEmpty(body);
 
-            var packet = new MqttConnAckPacket();
-
-            var acknowledgeFlags = body.ReadByte();
-
-            if (ProtocolVersion == MqttProtocolVersion.V311)
-            {
-                packet.IsSessionPresent = (acknowledgeFlags & 0x1) > 0;
-            }
+            var packet = new MqttV3ConnAckPacket();
 
+            body.ReadByte(); // Reserved.
             packet.ConnectReturnCode = (MqttConnectReturnCode)body.ReadByte();
 
             return packet;
         }
 
-        private static void ValidateConnectPacket(MqttConnectPacket packet)
+        protected void ValidateConnectPacket(MqttV3ConnectPacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
 
@@ -345,21 +312,12 @@ namespace MQTTnet.Serializer
             }
         }
 
-        private byte Serialize(MqttConnectPacket packet, MqttPacketWriter packetWriter)
+        protected virtual byte SerializeConnectPacket(MqttV3ConnectPacket packet, MqttPacketWriter packetWriter)
         {
             ValidateConnectPacket(packet);
 
-            // Write variable header
-            if (ProtocolVersion == MqttProtocolVersion.V311)
-            {
-                packetWriter.WriteWithLengthPrefix("MQTT");
-                packetWriter.Write(4); // 3.1.2.2 Protocol Level 4
-            }
-            else
-            {
-                packetWriter.WriteWithLengthPrefix("MQIsdp");
-                packetWriter.Write(3); // Protocol Level 3
-            }
+            packetWriter.WriteWithLengthPrefix("MQIsdp");
+            packetWriter.Write(3); // Protocol Level 3
 
             byte connectFlags = 0x0;
             if (packet.CleanSession)
@@ -416,33 +374,15 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Connect);
         }
 
-        private byte Serialize(MqttConnAckPacket packet, MqttPacketWriter packetWriter)
+        protected virtual byte SerializeConnAckPacket(MqttV3ConnAckPacket packet, MqttPacketWriter packetWriter)
         {
-            if (ProtocolVersion == MqttProtocolVersion.V310)
-            {
-                packetWriter.Write(0);
-            }
-            else if (ProtocolVersion == MqttProtocolVersion.V311)
-            {
-                byte connectAcknowledgeFlags = 0x0;
-                if (packet.IsSessionPresent)
-                {
-                    connectAcknowledgeFlags |= 0x1;
-                }
-
-                packetWriter.Write(connectAcknowledgeFlags);
-            }
-            else
-            {
-                throw new MqttProtocolViolationException("Protocol version not supported.");
-            }
-
+            packetWriter.Write(0); // Reserved.
             packetWriter.Write((byte)packet.ConnectReturnCode);
 
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.ConnAck);
         }
 
-        private static byte Serialize(MqttPubRelPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializePubRelPacket(MqttPubRelPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -454,7 +394,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRel, 0x02);
         }
 
-        private static byte Serialize(MqttPublishPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializePublishPacket(MqttPublishPacket packet, MqttPacketWriter packetWriter)
         {
             ValidatePublishPacket(packet);
 
@@ -499,7 +439,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Publish, fixedHeader);
         }
 
-        private static byte Serialize(MqttPubAckPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializePubAckPacket(MqttPubAckPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -511,7 +451,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubAck);
         }
 
-        private static byte Serialize(MqttPubRecPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializePubRecPacket(MqttPubRecPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -523,7 +463,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRec);
         }
 
-        private static byte Serialize(MqttPubCompPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializePubCompPacket(MqttPubCompPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -535,7 +475,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubComp);
         }
 
-        private static byte Serialize(MqttSubscribePacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializeSubscribePacket(MqttSubscribePacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.TopicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.8.3-3].");
 
@@ -558,7 +498,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Subscribe, 0x02);
         }
 
-        private static byte Serialize(MqttSubAckPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializeSubAckPacket(MqttSubAckPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -578,7 +518,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.SubAck);
         }
 
-        private static byte Serialize(MqttUnsubscribePacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializeUnsubscribePacket(MqttUnsubscribePacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.TopicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.10.3-2].");
 
@@ -600,7 +540,7 @@ namespace MQTTnet.Serializer
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
         }
 
-        private static byte Serialize(MqttUnsubAckPacket packet, MqttPacketWriter packetWriter)
+        private static byte SerializeUnsubAckPacket(MqttUnsubAckPacket packet, MqttPacketWriter packetWriter)
         {
             if (!packet.PacketIdentifier.HasValue)
             {
@@ -617,7 +557,7 @@ namespace MQTTnet.Serializer
         }
 
         // ReSharper disable once ParameterOnlyUsedForPreconditionCheck.Local
-        private static void ThrowIfBodyIsEmpty(MqttPacketBodyReader body)
+        protected static void ThrowIfBodyIsEmpty(MqttPacketBodyReader body)
         {
             if (body == null || body.Length == 0)
             {

Source/MQTTnet/Serializer/MqttV311PacketSerializer.cs

@@ -0,0 +1,100 @@
+using MQTTnet.Exceptions;
+using MQTTnet.Packets;
+using MQTTnet.Packets.V3;
+using MQTTnet.Protocol;
+
+namespace MQTTnet.Serializer
+{
+    public class MqttV311PacketSerializer : MqttV310PacketSerializer
+    {
+        protected override byte SerializeConnectPacket(MqttV3ConnectPacket packet, MqttPacketWriter packetWriter)
+        {
+            ValidateConnectPacket(packet);
+
+            packetWriter.WriteWithLengthPrefix("MQTT");
+            packetWriter.Write(4); // 3.1.2.2 Protocol Level 4
+
+            byte connectFlags = 0x0;
+            if (packet.CleanSession)
+            {
+                connectFlags |= 0x2;
+            }
+
+            if (packet.WillMessage != null)
+            {
+                connectFlags |= 0x4;
+                connectFlags |= (byte)((byte)packet.WillMessage.QualityOfServiceLevel << 3);
+
+                if (packet.WillMessage.Retain)
+                {
+                    connectFlags |= 0x20;
+                }
+            }
+
+            if (packet.Password != null && packet.Username == null)
+            {
+                throw new MqttProtocolViolationException("If the User Name Flag is set to 0, the Password Flag MUST be set to 0 [MQTT-3.1.2-22].");
+            }
+
+            if (packet.Password != null)
+            {
+                connectFlags |= 0x40;
+            }
+
+            if (packet.Username != null)
+            {
+                connectFlags |= 0x80;
+            }
+
+            packetWriter.Write(connectFlags);
+            packetWriter.Write(packet.KeepAlivePeriod);
+            packetWriter.WriteWithLengthPrefix(packet.ClientId);
+
+            if (packet.WillMessage != null)
+            {
+                packetWriter.WriteWithLengthPrefix(packet.WillMessage.Topic);
+                packetWriter.WriteWithLengthPrefix(packet.WillMessage.Payload);
+            }
+
+            if (packet.Username != null)
+            {
+                packetWriter.WriteWithLengthPrefix(packet.Username);
+            }
+
+            if (packet.Password != null)
+            {
+                packetWriter.WriteWithLengthPrefix(packet.Password);
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Connect);
+        }
+
+        protected override byte SerializeConnAckPacket(MqttV3ConnAckPacket packet, MqttPacketWriter packetWriter)
+        {
+            byte connectAcknowledgeFlags = 0x0;
+            if (packet.IsSessionPresent)
+            {
+                connectAcknowledgeFlags |= 0x1;
+            }
+
+            packetWriter.Write(connectAcknowledgeFlags);
+            packetWriter.Write((byte)packet.ConnectReturnCode);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.ConnAck);
+        }
+
+        protected override MqttBasePacket DeserializeConnAckPacket(MqttPacketBodyReader body)
+        {
+            ThrowIfBodyIsEmpty(body);
+
+            var packet = new MqttV3ConnAckPacket();
+
+            var acknowledgeFlags = body.ReadByte();
+
+            packet.IsSessionPresent = (acknowledgeFlags & 0x1) > 0;
+            packet.ConnectReturnCode = (MqttConnectReturnCode)body.ReadByte();
+
+            return packet;
+        }
+    }
+}

Source/MQTTnet/Serializer/MqttV500PacketSerializer.cs

@@ -0,0 +1,24 @@
+using System;
+using MQTTnet.Adapter;
+using MQTTnet.Packets;
+
+namespace MQTTnet.Serializer
+{
+    public class MqttV500PacketSerializer : IMqttPacketSerializer
+    {
+        public ArraySegment<byte> Serialize(MqttBasePacket mqttPacket)
+        {
+            throw new NotImplementedException();
+        }
+
+        public MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void FreeBuffer()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

Source/MQTTnet/Server/IMqttClientSession.cs

@@ -14,7 +14,7 @@ namespace MQTTnet.Server
         void EnqueueApplicationMessage(MqttClientSession senderClientSession, MqttPublishPacket publishPacket);
         void ClearPendingApplicationMessages();
         
-        Task RunAsync(MqttConnectPacket connectPacket, IMqttChannelAdapter adapter);
+        Task RunAsync(MqttApplicationMessage willMessage, int keepAliveInterval, IMqttChannelAdapter adapter);
         void Stop(MqttClientDisconnectType disconnectType);
 
         Task SubscribeAsync(IList<TopicFilter> topicFilters);

Source/MQTTnet/Server/MqttClientSession.cs

@@ -61,21 +61,20 @@ namespace MQTTnet.Server
             status.ClientId = ClientId;
             status.IsConnected = _adapter != null;
             status.Endpoint = _adapter?.Endpoint;
-            status.ProtocolVersion = _adapter?.PacketSerializer?.ProtocolVersion;
+            status.ProtocolVersion = _adapter?.PacketSerializerAdapter?.ProtocolVersion;
             status.PendingApplicationMessagesCount = _pendingPacketsQueue.Count;
             status.LastPacketReceived = _keepAliveMonitor.LastPacketReceived;
             status.LastNonKeepAlivePacketReceived = _keepAliveMonitor.LastNonKeepAlivePacketReceived;
         }
 
-        public Task RunAsync(MqttConnectPacket connectPacket, IMqttChannelAdapter adapter)
+        public Task RunAsync(MqttApplicationMessage willMessage, int keepAlivePeriod, IMqttChannelAdapter adapter)
         {
-            _workerTask = RunInternalAsync(connectPacket, adapter);
+            _workerTask = RunInternalAsync(willMessage, keepAlivePeriod, adapter);
             return _workerTask;
         }
 
-        private async Task RunInternalAsync(MqttConnectPacket connectPacket, IMqttChannelAdapter adapter)
+        private async Task RunInternalAsync(MqttApplicationMessage willMessage, int keepAlivePeriod, IMqttChannelAdapter adapter)
         {
-            if (connectPacket == null) throw new ArgumentNullException(nameof(connectPacket));
             if (adapter == null) throw new ArgumentNullException(nameof(adapter));
 
             try
@@ -94,10 +93,10 @@ namespace MQTTnet.Server
                 //endworkaround
 
                 _wasCleanDisconnect = false;
-                _willMessage = connectPacket.WillMessage;
+                _willMessage = willMessage;
 
                 _pendingPacketsQueue.Start(adapter, _cancellationTokenSource.Token);
-                _keepAliveMonitor.Start(connectPacket.KeepAlivePeriod, _cancellationTokenSource.Token);
+                _keepAliveMonitor.Start(keepAlivePeriod, _cancellationTokenSource.Token);
 
                 while (!_cancellationTokenSource.IsCancellationRequested)
                 {

Source/MQTTnet/Server/MqttClientSessionsManager.cs

@@ -9,6 +9,7 @@ using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
 using MQTTnet.Internal;
 using MQTTnet.Packets;
+using MQTTnet.Packets.V3;
 using MQTTnet.Protocol;
 
 namespace MQTTnet.Server
@@ -217,21 +218,18 @@ namespace MQTTnet.Server
                     return;
                 }
 
-                if (!(firstPacket is MqttConnectPacket connectPacket))
+                if (!(firstPacket is MqttV3ConnectPacket connectPacket))
                 {
                     throw new MqttProtocolViolationException("The first packet from a client must be a 'CONNECT' packet [MQTT-3.1.0-1].");
                 }
 
                 clientId = connectPacket.ClientId;
 
-                // Switch to the required protocol version before sending any response.
-                clientAdapter.PacketSerializer.ProtocolVersion = connectPacket.ProtocolVersion;
-
                 var connectReturnCode = ValidateConnection(connectPacket, clientAdapter);
                 if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
                 {
                     await clientAdapter.SendPacketAsync(
-                        new MqttConnAckPacket
+                        new MqttV3ConnAckPacket
                         {
                             ConnectReturnCode = connectReturnCode
                         },
@@ -244,7 +242,7 @@ namespace MQTTnet.Server
                 var clientSession = result.Session;
 
                 await clientAdapter.SendPacketAsync(
-                    new MqttConnAckPacket
+                    new MqttV3ConnAckPacket
                     {
                         ConnectReturnCode = connectReturnCode,
                         IsSessionPresent = result.IsExistingSession
@@ -253,7 +251,7 @@ namespace MQTTnet.Server
 
                 Server.OnClientConnected(clientId);
 
-                await clientSession.RunAsync(connectPacket, clientAdapter).ConfigureAwait(false);
+                await clientSession.RunAsync(connectPacket.WillMessage, connectPacket.KeepAlivePeriod, clientAdapter).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
             {
@@ -271,7 +269,7 @@ namespace MQTTnet.Server
             }
         }
 
-        private MqttConnectReturnCode ValidateConnection(MqttConnectPacket connectPacket, IMqttChannelAdapter clientAdapter)
+        private MqttConnectReturnCode ValidateConnection(MqttV3ConnectPacket connectPacket, IMqttChannelAdapter clientAdapter)
         {
             if (_options.ConnectionValidator == null)
             {
@@ -289,7 +287,7 @@ namespace MQTTnet.Server
             return context.ReturnCode;
         }
 
-        private PrepareClientSessionResult PrepareClientSession(MqttConnectPacket connectPacket)
+        private PrepareClientSessionResult PrepareClientSession(MqttV3ConnectPacket connectPacket)
         {
             lock (_sessions)
             {

Tests/MQTTnet.AspNetCore.Tests/ReaderExtensionsTest.cs

@@ -1,3 +1,4 @@
+#if NETCOREAPP
 using System.Buffers;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.AspNetCore;
@@ -12,7 +13,7 @@ namespace MQTTnet.AspNetCore.Tests
         [TestMethod]
         public void TestTryDeserialize()
         {
-            var serializer = new MqttPacketSerializer();
+            var serializer = new MqttV311PacketSerializer();
 
             var buffer = serializer.Serialize(new MqttPublishPacket() {Topic = "a", Payload = new byte[5]});
 
@@ -43,3 +44,4 @@ namespace MQTTnet.AspNetCore.Tests
         }
     }
 }
+#endif

Tests/MQTTnet.Benchmarks/ChannelAdapterBenchmark.cs

@@ -26,7 +26,8 @@ namespace MQTTnet.Benchmarks
                 .Build();
 
             _packet = message.ToPublishPacket();
-            var serializer = new MqttPacketSerializer();
+            var serializer = new MqttPacketSerializerAdapter(MqttProtocolVersion.V311);
+            
             var serializedPacket = Join(serializer.Serialize(_packet));
 
             _iterations = 10000;

Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -19,7 +19,7 @@ namespace MQTTnet.Benchmarks
     {
         private MqttBasePacket _packet;
         private ArraySegment<byte> _serializedPacket;
-        private MqttPacketSerializer _serializer;
+        private IMqttPacketSerializer _serializer;
 
         [GlobalSetup]
         public void Setup()
@@ -29,7 +29,7 @@ namespace MQTTnet.Benchmarks
                 .Build();
 
             _packet = message.ToPublishPacket();
-            _serializer = new MqttPacketSerializer();
+            _serializer = new MqttV311PacketSerializer();
             _serializedPacket = _serializer.Serialize(_packet);
         }
 

Tests/MQTTnet.Core.Tests/MqttClientTests.cs

@@ -8,6 +8,7 @@ using MQTTnet.Client;
 using MQTTnet.Diagnostics;
 using MQTTnet.Exceptions;
 using MQTTnet.Packets;
+using MQTTnet.Packets.V3;
 
 namespace MQTTnet.Core.Tests
 {
@@ -50,7 +51,7 @@ namespace MQTTnet.Core.Tests
 
             Task.Run(async () => {
                 var connect = await channel2.ReceivePacketAsync(TimeSpan.Zero, CancellationToken.None);
-                await channel2.SendPacketAsync(new MqttConnAckPacket() { ConnectReturnCode = Protocol.MqttConnectReturnCode.ConnectionRefusedNotAuthorized }, CancellationToken.None);
+                await channel2.SendPacketAsync(new MqttV3ConnAckPacket() { ConnectReturnCode = Protocol.MqttConnectReturnCode.ConnectionRefusedNotAuthorized }, CancellationToken.None);
             });
 
 

Tests/MQTTnet.Core.Tests/MqttKeepAliveMonitorTests.cs

@@ -77,7 +77,7 @@ namespace MQTTnet.Core.Tests
                 throw new NotSupportedException();
             }
 
-            public Task RunAsync(MqttConnectPacket connectPacket, IMqttChannelAdapter adapter)
+            public Task RunAsync(MqttApplicationMessage willMessage, int keepAlivePeriod, IMqttChannelAdapter adapter)
             {
                 throw new NotSupportedException();
             }

Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs

@@ -7,6 +7,7 @@ using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Adapter;
 using MQTTnet.Internal;
 using MQTTnet.Packets;
+using MQTTnet.Packets.V3;
 using MQTTnet.Protocol;
 using MQTTnet.Serializer;
 
@@ -18,7 +19,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void SerializeV310_MqttConnectPacket()
         {
-            var p = new MqttConnectPacket
+            var p = new MqttV3ConnectPacket
             {
                 ClientId = "XYZ",
                 Password = "PASS",
@@ -33,7 +34,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void SerializeV311_MqttConnectPacket()
         {
-            var p = new MqttConnectPacket
+            var p = new MqttV3ConnectPacket
             {
                 ClientId = "XYZ",
                 Password = "PASS",
@@ -48,7 +49,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void SerializeV311_MqttConnectPacketWithWillMessage()
         {
-            var p = new MqttConnectPacket
+            var p = new MqttV3ConnectPacket
             {
                 ClientId = "XYZ",
                 Password = "PASS",
@@ -70,7 +71,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void DeserializeV311_MqttConnectPacket()
         {
-            var p = new MqttConnectPacket
+            var p = new MqttV3ConnectPacket
             {
                 ClientId = "XYZ",
                 Password = "PASS",
@@ -85,7 +86,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void DeserializeV311_MqttConnectPacketWithWillMessage()
         {
-            var p = new MqttConnectPacket
+            var p = new MqttV3ConnectPacket
             {
                 ClientId = "XYZ",
                 Password = "PASS",
@@ -107,7 +108,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void SerializeV311_MqttConnAckPacket()
         {
-            var p = new MqttConnAckPacket
+            var p = new MqttV3ConnAckPacket
             {
                 IsSessionPresent = true,
                 ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
@@ -119,7 +120,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void SerializeV310_MqttConnAckPacket()
         {
-            var p = new MqttConnAckPacket
+            var p = new MqttV3ConnAckPacket
             {
                 ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
             };
@@ -130,7 +131,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void DeserializeV311_MqttConnAckPacket()
         {
-            var p = new MqttConnAckPacket
+            var p = new MqttV3ConnAckPacket
             {
                 IsSessionPresent = true,
                 ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
@@ -142,7 +143,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void DeserializeV310_MqttConnAckPacket()
         {
-            var p = new MqttConnAckPacket
+            var p = new MqttV3ConnAckPacket
             {
                 ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
             };
@@ -153,7 +154,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void Serialize_LargePacket()
         {
-            var serializer = new MqttPacketSerializer { ProtocolVersion = MqttProtocolVersion.V311 };
+            var serializer = new MqttV311PacketSerializer();
 
             const int payloadLength = 80000;
 
@@ -509,7 +510,20 @@ namespace MQTTnet.Core.Tests
 
         private static void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
-            var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
+            IMqttPacketSerializer serializer;
+            if (protocolVersion == MqttProtocolVersion.V311)
+            {
+                serializer = new MqttV311PacketSerializer();
+            }
+            else if (protocolVersion == MqttProtocolVersion.V310)
+            {
+                serializer = new MqttV310PacketSerializer();
+            }
+            else
+            {
+                throw new NotSupportedException();
+            }
+
             var data = serializer.Serialize(packet);
 
             Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(Join(data)));
@@ -517,7 +531,19 @@ namespace MQTTnet.Core.Tests
 
         private static void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
-            var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
+            IMqttPacketSerializer serializer;
+            if (protocolVersion == MqttProtocolVersion.V311)
+            {
+                serializer = new MqttV311PacketSerializer();
+            }
+            else if (protocolVersion == MqttProtocolVersion.V310)
+            {
+                serializer = new MqttV310PacketSerializer();
+            }
+            else
+            {
+                throw new NotSupportedException();
+            }
 
             var buffer1 = serializer.Serialize(packet);
 
@@ -541,7 +567,19 @@ namespace MQTTnet.Core.Tests
         private static T Roundtrip<T>(T packet, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
             where T : MqttBasePacket
         {
-            var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
+            IMqttPacketSerializer serializer;
+            if (protocolVersion == MqttProtocolVersion.V311)
+            {
+                serializer = new MqttV311PacketSerializer();
+            }
+            else if (protocolVersion == MqttProtocolVersion.V310)
+            {
+                serializer = new MqttV310PacketSerializer();
+            }
+            else
+            {
+                throw new NotSupportedException();
+            }
 
             var buffer1 = serializer.Serialize(packet);
 

Tests/MQTTnet.Core.Tests/MqttServerTests.cs

@@ -171,14 +171,14 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public async Task MqttServer_Publish_MultipleClients()
         {
-            var serverAdapter = new MqttTcpServerAdapter(new MqttNetLogger().CreateChildLogger());
-            var s = new MqttFactory().CreateMqttServer(new[] { serverAdapter }, new MqttNetLogger());
+            var s = new MqttFactory().CreateMqttServer();
             var receivedMessagesCount = 0;
             var locked = new object();
 
             var clientOptions = new MqttClientOptionsBuilder()
                 .WithTcpServer("localhost")
                 .Build();
+
             var clientOptions2 = new MqttClientOptionsBuilder()
                 .WithTcpServer("localhost")
                 .Build();

Tests/MQTTnet.Core.Tests/TestMqttCommunicationAdapter.cs

@@ -16,7 +16,7 @@ namespace MQTTnet.Core.Tests
 
         public string Endpoint { get; }
 
-        public IMqttPacketSerializer PacketSerializer { get; } = new MqttPacketSerializer();
+        public MqttPacketSerializerAdapter PacketSerializerAdapter { get; } = new MqttPacketSerializerAdapter(MqttProtocolVersion.V311);
 
         public event EventHandler ReadingPacketStarted;
         public event EventHandler ReadingPacketCompleted;

Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml.cs

@@ -14,6 +14,7 @@ using MQTTnet.Extensions.ManagedClient;
 using MQTTnet.Extensions.Rpc;
 using MQTTnet.Implementations;
 using MQTTnet.Protocol;
+using MQTTnet.Serializer;
 using MQTTnet.Server;
 using MqttClientConnectedEventArgs = MQTTnet.Client.MqttClientConnectedEventArgs;
 using MqttClientDisconnectedEventArgs = MQTTnet.Client.MqttClientDisconnectedEventArgs;
@@ -87,7 +88,8 @@ namespace MQTTnet.TestApp.UniversalWindows
 
             var options = new MqttClientOptions
             {
-                ClientId = ClientId.Text
+                ClientId = ClientId.Text,
+                ProtocolVersion = MqttProtocolVersion.V500
             };
 
             if (UseTcp.IsChecked == true)