Update documents

Bug fixes v3

.bettercodehub.yml

@@ -0,0 +1,8 @@
+exclude:
+- /Frameworks/.*
+- /MQTTnet.TestApp.NetCore/Program.cs
+- /Tests/MQTTnet.TestApp.NetFramework/.*
+- /Tests/MQTTnet.TestApp.UniversalWindows/.*
+component_depth: 1
+languages:
+- csharp

.gitignore

@@ -286,4 +286,6 @@ __pycache__/
 *.btm.cs
 *.odx.cs
 *.xsd.cs
+
+
 Build/nuget.exe

.travis.yml

@@ -0,0 +1,10 @@
+language: csharp
+solution: MQTTnet.sln
+
+matrix:
+  include:
+    - dotnet: 2.0.0
+      mono: none
+      dist: trusty
+      env: DOTNETCORE=1  # optional, can be used to take different code paths in your script
+    - mono: latest

Build/MQTTnet.nuspec

@@ -2,7 +2,7 @@
 <package >
   <metadata>
     <id>MQTTnet</id>
-    <version>2.1.5.1</version>
+    <version>2.3.1</version>
     <authors>Christian Kratky</authors>
     <owners>Christian Kratky</owners>
     <licenseUrl>https://github.com/chkr1011/MQTTnet/blob/master/LICENSE</licenseUrl>
@@ -10,19 +10,22 @@
     <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker).</description>
-    <releaseNotes>* [Server] Fixed wrong handling of QoS levels
+    <releaseNotes>* [Server] Fixed an issue when accepting a new connection (UWP only) (Thanks to haeberle)
+[Core] Fixed a dead lock while sending messages (Thanks to 1liveowl, JanEggers)
+[Client] The client is no longer sending packets before receiving has started
+[Core] Minor changes and improvements
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2017</copyright>
-    <tags>MQTT MQTTClient MQTTServer MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Queue Hardware</tags> 
+    <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M</tags> 
     <dependencies>
 
       <group targetFramework="netstandard1.3">
         <dependency id="NETStandard.Library" version="1.6.1" />
-        <dependency id="System.Net.Security" version="4.3.1" />
+        <dependency id="System.Net.Security" version="4.3.2" />
       </group>
       
       <group targetFramework="uap10.0">
-        <dependency id="Microsoft.NETCore.UniversalWindowsPlatform" version="5.3.3" />
+        <dependency id="Microsoft.NETCore.UniversalWindowsPlatform" version="5.4.0" />
       </group>
 
     </dependencies>

Frameworks/MQTTnet.NetFramework/Implementations/MqttServerAdapter.cs

@@ -85,13 +85,18 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null);
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new MqttV311PacketSerializer());
+                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null).ConfigureAwait(false);
+
+                    var tcpChannel = new MqttTcpChannel(clientSocket, null);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(tcpChannel, new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception) when (!(exception is ObjectDisposedException))
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
+
+                    //excessive CPU consumed if in endless loop of socket errors
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }
@@ -102,17 +107,21 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null);
+                    var clientSocket = await Task.Factory.FromAsync(_tlsEndpointSocket.BeginAccept, _tlsEndpointSocket.EndAccept, null).ConfigureAwait(false);
 
                     var sslStream = new SslStream(new NetworkStream(clientSocket));
-                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false);
-                    
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttV311PacketSerializer());
+                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false).ConfigureAwait(false);
+
+                    var tcpChannel = new MqttTcpChannel(clientSocket, sslStream);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(tcpChannel, new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at TLS endpoint.");
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
+
+                    //excessive CPU consumed if in endless loop of socket errors
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }

Frameworks/MQTTnet.NetFramework/Implementations/MqttTcpChannel.cs

@@ -6,108 +6,95 @@ using System.Security.Cryptography.X509Certificates;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
+using System.IO;
 
 namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
-        private readonly Socket _socket;
+        // ReSharper disable once MemberCanBePrivate.Global
+        // ReSharper disable once AutoPropertyCanBeMadeGetOnly.Global
+        public static int BufferSize { get; set; } = 4096 * 20; // Can be changed for fine tuning by library user.
+
+        private Socket _socket;
         private SslStream _sslStream;
 
+        /// <summary>
+        /// called on client sockets are created in connect
+        /// </summary>
         public MqttTcpChannel()
         {
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+
         }
 
+        /// <summary>
+        /// called on server, sockets are passed in
+        /// connect will not be called
+        /// </summary>
         public MqttTcpChannel(Socket socket, SslStream sslStream)
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
             _sslStream = sslStream;
+            CreateStreams(socket, sslStream);
         }
 
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream { get; private set; }
+
         public async Task ConnectAsync(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
-            try
-            {
-                await Task.Factory.FromAsync(_socket.BeginConnect, _socket.EndConnect, options.Server, options.GetPort(), null);
 
-                if (options.TlsOptions.UseTls)
-                {
-                    _sslStream = new SslStream(new NetworkStream(_socket, true));
-                    await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation);
-                }
-            }
-            catch (SocketException exception)
+            if (_socket == null)
             {
-                throw new MqttCommunicationException(exception);
+                _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
             }
+
+            await Task.Factory.FromAsync(_socket.BeginConnect, _socket.EndConnect, options.Server, options.GetPort(), null).ConfigureAwait(false);
+
+            if (options.TlsOptions.UseTls)
+            {
+                _sslStream = new SslStream(new NetworkStream(_socket, true));
+
+                await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation).ConfigureAwait(false);
+            }
+
+            CreateStreams(_socket, _sslStream);
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                _sslStream.Dispose();
-                _socket.Dispose();
-                return Task.FromResult(0);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                if (_sslStream != null)
-                {
-                    return _sslStream.WriteAsync(buffer, 0, buffer.Length);
-                }
-
-                return Task.Factory.FromAsync(
-                    // ReSharper disable once AssignNullToNotNullAttribute
-                    _socket.BeginSend(buffer, 0, buffer.Length, SocketFlags.None, null, null),
-                    _socket.EndSend);
-
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public Task ReadAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                if (_sslStream != null)
-                {
-                    return _sslStream.ReadAsync(buffer, 0, buffer.Length);
-                }
-
-                return Task.Factory.FromAsync(
-                    // ReSharper disable once AssignNullToNotNullAttribute
-                    _socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, null, null),
-                    _socket.EndReceive);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
+            Dispose();
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
+            RawReceiveStream?.Dispose();
+            RawReceiveStream = null;
+
+            ReceiveStream?.Dispose();
+            ReceiveStream = null;
+
+            SendStream?.Dispose();
+            SendStream = null;
+
             _socket?.Dispose();
+            _socket = null;
+
             _sslStream?.Dispose();
+            _sslStream = null;
+        }
+
+        private void CreateStreams(Socket socket, Stream sslStream)
+        {
+            RawReceiveStream = sslStream ?? new NetworkStream(socket);
+
+            //cannot use this as default buffering prevents from receiving the first connect message
+            //need two streams otherwise read and write have to be synchronized
+            SendStream = new BufferedStream(RawReceiveStream, BufferSize);
+            ReceiveStream = new BufferedStream(RawReceiveStream, BufferSize);
         }
 
         private static X509CertificateCollection LoadCertificates(MqttClientOptions options)

Frameworks/MQTTnet.NetFramework/Implementations/MqttWebSocketChannel.cs

@@ -0,0 +1,55 @@
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private ClientWebSocket _webSocket;
+
+        public Stream RawReceiveStream { get; private set; }
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            var uri = options.Server;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+
+            if (options.Port.HasValue)
+            {
+                uri += ":" + options.Port;
+            }
+            
+            _webSocket = new ClientWebSocket();
+            _webSocket.Options.KeepAliveInterval = options.KeepAlivePeriod;
+            await _webSocket.ConnectAsync(new Uri(uri), CancellationToken.None).ConfigureAwait(false);
+            RawReceiveStream = new WebSocketStream(_webSocket);
+        }
+
+        public async Task DisconnectAsync()
+        {
+            RawReceiveStream = null;
+
+            if (_webSocket == null)
+            {
+                return;
+            }
+
+            await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
+        }
+
+        public void Dispose()
+        {
+            _webSocket?.Dispose();
+        }
+    }
+}

Frameworks/MQTTnet.NetFramework/Implementations/WebSocketStream.cs

@@ -0,0 +1,77 @@
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public class WebSocketStream : Stream
+    {
+        private readonly ClientWebSocket _webSocket;
+
+        public WebSocketStream(ClientWebSocket webSocket)
+        {
+            _webSocket = webSocket;
+        }
+
+        public override void Flush()
+        {
+        }
+
+        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            var currentOffset = offset;
+            var targetOffset = offset + count;
+            while (_webSocket.State == WebSocketState.Open && currentOffset < targetOffset)
+            {
+                var response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, currentOffset, count), cancellationToken).ConfigureAwait(false);
+                currentOffset += response.Count;
+
+                if (response.MessageType == WebSocketMessageType.Close)
+                {
+                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            return currentOffset - offset;
+        }
+
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            return _webSocket.SendAsync(new ArraySegment<byte>(buffer, offset, count), WebSocketMessageType.Binary, true, cancellationToken);
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return ReadAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            WriteAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override bool CanRead => true;
+        public override bool CanSeek => false;
+        public override bool CanWrite => true;
+
+        public override long Length => throw new NotSupportedException();
+
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.NetFramework/MQTTnet.NetFramework.csproj

@@ -100,6 +100,8 @@
     <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Implementations\MqttWebSocketChannel.cs" />
+    <Compile Include="Implementations\WebSocketStream.cs" />
     <Compile Include="MqttClientFactory.cs" />
     <Compile Include="MqttServerFactory.cs" />
     <Compile Include="Implementations\MqttServerAdapter.cs" />

Frameworks/MQTTnet.NetFramework/MqttClientFactory.cs

@@ -1,18 +1,33 @@
 using System;
 using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
         public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttV311PacketSerializer()));
+            return new MqttClient(options, new MqttChannelCommunicationAdapter(GetMqttCommunicationChannel(options), new MqttPacketSerializer()));
+        }
+
+        private static IMqttCommunicationChannel GetMqttCommunicationChannel(MqttClientOptions options)
+        {
+            switch (options.ConnectionType)
+            {
+                case MqttConnectionType.Tcp:
+                    return new MqttTcpChannel();
+                case MqttConnectionType.Ws:
+                    return new MqttWebSocketChannel();
+
+                default:
+                    throw new NotSupportedException();
+            }
         }
     }
 }

Frameworks/MQTTnet.NetFramework/MqttServerFactory.cs

@@ -6,7 +6,7 @@ using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttServerFactory
+    public class MqttServerFactory : IMqttServerFactory
     {
         public IMqttServer CreateMqttServer(MqttServerOptions options)
         {

Frameworks/MQTTnet.NetFramework/Properties/AssemblyInfo.cs

@@ -11,5 +11,5 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyCulture("")]
 [assembly: ComVisible(false)]
 [assembly: Guid("a480ef90-0eaa-4d9a-b271-47a9c47f6f7d")]
-[assembly: AssemblyVersion("2.1.5.1")]
-[assembly: AssemblyFileVersion("2.1.5.1")]
+[assembly: AssemblyVersion("2.3.1.0")]
+[assembly: AssemblyFileVersion("2.3.1.0")]

Frameworks/MQTTnet.NetStandard/Implementations/MqttServerAdapter.cs

@@ -27,6 +27,7 @@ namespace MQTTnet.Implementations
         public void Start(MqttServerOptions options)
         {
             if (_isRunning) throw new InvalidOperationException("Server is already started.");
+
             _isRunning = true;
 
             _cancellationTokenSource = new CancellationTokenSource();
@@ -83,13 +84,16 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await _defaultEndpointSocket.AcceptAsync();
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new MqttV311PacketSerializer());
+                    var clientSocket = await _defaultEndpointSocket.AcceptAsync().ConfigureAwait(false);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
+
+                    //excessive CPU consumed if in endless loop of socket errors
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }
@@ -100,17 +104,20 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await _defaultEndpointSocket.AcceptAsync();
+                    var clientSocket = await _tlsEndpointSocket.AcceptAsync().ConfigureAwait(false);
 
                     var sslStream = new SslStream(new NetworkStream(clientSocket));
-                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false);
-                    
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttV311PacketSerializer());
+                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false).ConfigureAwait(false);
+
+                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at TLS endpoint.");
+                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
+
+                    //excessive CPU consumed if in endless loop of socket errors
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs

@@ -6,101 +6,73 @@ using System.Security.Cryptography.X509Certificates;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
+using System.IO;
 
 namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
-        private readonly Socket _socket;
+        private Socket _socket;
         private SslStream _sslStream;
-
+        
+        /// <summary>
+        /// called on client sockets are created in connect
+        /// </summary>
         public MqttTcpChannel()
         {
-            _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
         }
 
+        /// <summary>
+        /// called on server, sockets are passed in
+        /// connect will not be called
+        /// </summary>
         public MqttTcpChannel(Socket socket, SslStream sslStream)
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
             _sslStream = sslStream;
+            ReceiveStream = (Stream)sslStream ?? new NetworkStream(socket);
         }
 
+        public Stream SendStream => ReceiveStream;
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream => ReceiveStream;
+        
         public async Task ConnectAsync(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
-            try
+
+            if (_socket == null)
             {
-                await _socket.ConnectAsync(options.Server, options.GetPort());
-                
-                if (options.TlsOptions.UseTls)
-                {
-                    _sslStream = new SslStream(new NetworkStream(_socket, true));
-                    await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation);
-                }
+                _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
             }
-            catch (SocketException exception)
+
+            await _socket.ConnectAsync(options.Server, options.GetPort()).ConfigureAwait(false);
+
+            if (options.TlsOptions.UseTls)
             {
-                throw new MqttCommunicationException(exception);
+                _sslStream = new SslStream(new NetworkStream(_socket, true));
+                ReceiveStream = _sslStream;
+                await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation).ConfigureAwait(false);
+            }
+            else
+            {
+                ReceiveStream = new NetworkStream(_socket);
             }
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                _sslStream.Dispose();
-                _socket.Dispose();
-                return Task.FromResult(0);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                if (_sslStream != null)
-                {
-                    return _sslStream.WriteAsync(buffer, 0, buffer.Length);
-                }
-
-                return _socket.SendAsync(new ArraySegment<byte>(buffer), SocketFlags.None);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public Task ReadAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                if (_sslStream != null)
-                {
-                    return _sslStream.ReadAsync(buffer, 0, buffer.Length);
-                }
-
-                return _socket.ReceiveAsync(new ArraySegment<byte>(buffer), SocketFlags.None);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
+            Dispose();
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
             _socket?.Dispose();
+            _socket = null;
+
             _sslStream?.Dispose();
+            _sslStream = null;
         }
 
         private static X509CertificateCollection LoadCertificates(MqttClientOptions options)

Frameworks/MQTTnet.NetStandard/Implementations/MqttWebSocketChannel.cs

@@ -0,0 +1,55 @@
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private ClientWebSocket _webSocket;
+
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+        public Stream RawReceiveStream { get; private set; }
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            var uri = options.Server;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+
+            if (options.Port.HasValue)
+            {
+                uri += ":" + options.Port;
+            }
+            
+            _webSocket = new ClientWebSocket();
+            _webSocket.Options.KeepAliveInterval = options.KeepAlivePeriod;
+            await _webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
+            RawReceiveStream = new WebSocketStream(_webSocket);
+        }
+
+        public async Task DisconnectAsync()
+        {
+            RawReceiveStream = null;
+
+            if (_webSocket == null)
+            {
+                return;
+            }
+
+            await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
+        }
+
+        public void Dispose()
+        {
+            _webSocket?.Dispose();
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/Implementations/WebSocketStream.cs

@@ -0,0 +1,79 @@
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public class WebSocketStream : Stream
+    {
+        private readonly ClientWebSocket _webSocket;
+        
+        public WebSocketStream(ClientWebSocket webSocket)
+        {
+            _webSocket = webSocket;
+        }
+
+        public override bool CanRead => true;
+
+        public override bool CanSeek => false;
+
+        public override bool CanWrite => true;
+
+        public override long Length => throw new NotSupportedException();
+
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        public override void Flush()
+        {
+        }
+
+        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            var currentOffset = offset;
+            var targetOffset = offset + count;
+            while (_webSocket.State == WebSocketState.Open && currentOffset < targetOffset)
+            {
+                var response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, currentOffset, count), cancellationToken).ConfigureAwait(false);
+                currentOffset += response.Count;
+
+                if (response.MessageType == WebSocketMessageType.Close)
+                {
+                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            return currentOffset - offset;
+        }
+
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            return _webSocket.SendAsync(new ArraySegment<byte>(buffer, offset, count), WebSocketMessageType.Binary, true, cancellationToken);
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return ReadAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            WriteAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/MQTTnet.Netstandard.csproj

@@ -4,8 +4,8 @@
     <TargetFramework>netstandard1.3</TargetFramework>
     <AssemblyName>MQTTnet</AssemblyName>
     <RootNamespace>MQTTnet</RootNamespace>
-    <AssemblyVersion>2.1.5.1</AssemblyVersion>
-    <FileVersion>2.1.5.1</FileVersion>
+    <AssemblyVersion>2.3.1.0</AssemblyVersion>
+    <FileVersion>2.3.1.0</FileVersion>
     <Version>0.0.0.0</Version>
     <Company />
     <Product />
@@ -23,7 +23,10 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="System.Net.Security" Version="4.3.1" />
+    <PackageReference Include="System.Net.Security" Version="4.3.2" />
+    <PackageReference Include="System.Net.WebSockets" Version="4.3.0" />
+    <PackageReference Include="System.Net.WebSockets.Client" Version="4.3.1" />
+    <PackageReference Include="System.Threading.Thread" Version="4.3.0" />
   </ItemGroup>
 
 </Project>

Frameworks/MQTTnet.NetStandard/MqttClientFactory.cs

@@ -1,18 +1,33 @@
 using System;
 using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
         public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttV311PacketSerializer()));
+            return new MqttClient(options, new MqttChannelCommunicationAdapter(GetMqttCommunicationChannel(options), new MqttPacketSerializer()));
+        }
+
+        private static IMqttCommunicationChannel GetMqttCommunicationChannel(MqttClientOptions options)
+        {
+            switch (options.ConnectionType)
+            {
+                case MqttConnectionType.Tcp:
+                    return new MqttTcpChannel();
+                case MqttConnectionType.Ws:
+                    return new MqttWebSocketChannel();
+
+                default:
+                    throw new NotSupportedException();
+            }
         }
     }
-}
+}

Frameworks/MQTTnet.NetStandard/MqttServerFactory.cs

@@ -6,7 +6,7 @@ using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttServerFactory
+    public class MqttServerFactory : IMqttServerFactory
     {
         public IMqttServer CreateMqttServer(MqttServerOptions options)
         {

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttServerAdapter.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Implementations
     public class MqttServerAdapter : IMqttServerAdapter, IDisposable
     {
         private StreamSocketListener _defaultEndpointSocket;
-        
+
         private bool _isRunning;
 
         public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
@@ -20,13 +20,14 @@ namespace MQTTnet.Implementations
             if (options == null) throw new ArgumentNullException(nameof(options));
 
             if (_isRunning) throw new InvalidOperationException("Server is already started.");
+
             _isRunning = true;
 
             if (options.DefaultEndpointOptions.IsEnabled)
             {
                 _defaultEndpointSocket = new StreamSocketListener();
                 _defaultEndpointSocket.BindServiceNameAsync(options.GetDefaultEndpointPort().ToString(), SocketProtectionLevel.PlainSocket).GetAwaiter().GetResult();
-                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;                
+                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;
             }
 
             if (options.TlsEndpointOptions.IsEnabled)
@@ -52,12 +53,12 @@ namespace MQTTnet.Implementations
         {
             try
             {
-                var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(args.Socket), new MqttV311PacketSerializer());
+                var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(args.Socket), new MqttPacketSerializer());
                 ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(args.Socket.Information.RemoteAddress.ToString(), clientAdapter));
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while acceping connection at default endpoint.");
+                MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
             }
         }
     }

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs

@@ -1,105 +1,89 @@
 using System;
+using System.IO;
 using System.Linq;
-using System.Net.Sockets;
 using System.Runtime.InteropServices.WindowsRuntime;
 using System.Threading.Tasks;
 using Windows.Networking;
 using Windows.Networking.Sockets;
 using Windows.Security.Cryptography.Certificates;
-using Windows.Storage.Streams;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
 
 namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
-        private readonly StreamSocket _socket;
+        private StreamSocket _socket;
 
         public MqttTcpChannel()
         {
-            _socket = new StreamSocket();
         }
 
         public MqttTcpChannel(StreamSocket socket)
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
+            CreateStreams();
         }
 
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream { get; private set; }
+
         public async Task ConnectAsync(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
-            try
-            {
-                if (!options.TlsOptions.UseTls)
-                {
-                    await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString());
-                }
-                else
-                {
-                    _socket.Control.ClientCertificate = LoadCertificate(options);
 
-                    if (!options.TlsOptions.CheckCertificateRevocation)
-                    {
-                        _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.IncompleteChain);
-                        _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.RevocationInformationMissing);
-                    }
-
-                    await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString(), SocketProtectionLevel.Tls12);
-                }
-            }
-            catch (SocketException exception)
+            if (_socket == null)
             {
-                throw new MqttCommunicationException(exception);
+                _socket = new StreamSocket();
             }
+
+            if (!options.TlsOptions.UseTls)
+            {
+                await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString());
+            }
+            else
+            {
+                _socket.Control.ClientCertificate = LoadCertificate(options);
+
+                if (!options.TlsOptions.CheckCertificateRevocation)
+                {
+                    _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.IncompleteChain);
+                    _socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.RevocationInformationMissing);
+                }
+
+                await _socket.ConnectAsync(new HostName(options.Server), options.GetPort().ToString(), SocketProtectionLevel.Tls12);
+            }
+
+            CreateStreams();
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                _socket.Dispose();
-                return Task.FromResult(0);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await _socket.OutputStream.WriteAsync(buffer.AsBuffer());
-                await _socket.OutputStream.FlushAsync();
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task ReadAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await _socket.InputStream.ReadAsync(buffer.AsBuffer(), (uint)buffer.Length, InputStreamOptions.None);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
+            Dispose();
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
+            RawReceiveStream?.Dispose();
+            RawReceiveStream = null;
+
+            SendStream?.Dispose();
+            SendStream = null;
+
+            ReceiveStream?.Dispose();
+            ReceiveStream = null;
+
             _socket?.Dispose();
+            _socket = null;
+        }
+
+        private void CreateStreams()
+        {
+            SendStream = _socket.OutputStream.AsStreamForWrite();
+            ReceiveStream = _socket.InputStream.AsStreamForRead();
+            RawReceiveStream = ReceiveStream;
         }
 
         private static Certificate LoadCertificate(MqttClientOptions options)

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttWebSocketChannel.cs

@@ -0,0 +1,56 @@
+using MQTTnet.Core.Channel;
+using MQTTnet.Core.Client;
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private ClientWebSocket _webSocket = new ClientWebSocket();
+
+        public Stream RawReceiveStream { get; private set; }
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+
+        public async Task ConnectAsync(MqttClientOptions options)
+        {
+            var uri = options.Server;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+
+            if (options.Port.HasValue)
+            {
+                uri += ":" + options.Port;
+            }
+            
+            _webSocket = new ClientWebSocket();
+            _webSocket.Options.KeepAliveInterval = options.KeepAlivePeriod;
+            await _webSocket.ConnectAsync(new Uri(uri), CancellationToken.None).ConfigureAwait(false);
+
+            RawReceiveStream = new WebSocketStream(_webSocket);
+        }
+
+        public async Task DisconnectAsync()
+        {
+            RawReceiveStream = null;
+
+            if (_webSocket == null)
+            {
+                return;
+            }
+
+            await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
+        }
+
+        public void Dispose()
+        {
+            _webSocket?.Dispose();
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/Implementations/WebSocketStream.cs

@@ -0,0 +1,77 @@
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Implementations
+{
+    public class WebSocketStream : Stream
+    {
+        private readonly ClientWebSocket _webSocket;
+
+        public WebSocketStream(ClientWebSocket webSocket)
+        {
+            _webSocket = webSocket;
+        }
+
+        public override void Flush()
+        {
+        }
+
+        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            var currentOffset = offset;
+            var targetOffset = offset + count;
+            while (_webSocket.State == WebSocketState.Open && currentOffset < targetOffset)
+            {
+                var response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, currentOffset, count), cancellationToken).ConfigureAwait(false);
+                currentOffset += response.Count;
+                
+                if (response.MessageType == WebSocketMessageType.Close)
+                {
+                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            return currentOffset - offset;
+        }
+
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            return _webSocket.SendAsync(new ArraySegment<byte>(buffer, offset, count), WebSocketMessageType.Binary, true, cancellationToken);
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return ReadAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            WriteAsync(buffer, offset, count).GetAwaiter().GetResult();
+        }
+
+        public override bool CanRead => true;
+        public override bool CanSeek => false;
+        public override bool CanWrite => true;
+
+        public override long Length => throw new NotSupportedException();
+
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/MQTTnet.UniversalWindows.csproj

@@ -110,11 +110,13 @@
     <DocumentationFile>bin\x64\Release\MQTTnet.XML</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="Implementations\MqttWebSocketChannel.cs" />
     <Compile Include="MqttClientFactory.cs" />
     <Compile Include="Implementations\MqttServerAdapter.cs" />
-    <Compile Include="MqttServerFactory.cs" />
     <Compile Include="Implementations\MqttTcpChannel.cs" />
+    <Compile Include="MqttServerFactory.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Implementations\WebSocketStream.cs" />
     <EmbeddedResource Include="Properties\MQTTnet.Universal.rd.xml" />
   </ItemGroup>
   <ItemGroup>
@@ -125,7 +127,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
-      <Version>5.3.3</Version>
+      <Version>5.4.0</Version>
     </PackageReference>
   </ItemGroup>
   <PropertyGroup Condition=" '$(VisualStudioVersion)' == '' or '$(VisualStudioVersion)' &lt; '14.0' ">

Frameworks/MQTTnet.UniversalWindows/MqttClientFactory.cs

@@ -1,18 +1,33 @@
 using System;
 using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Serializer;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
         public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttV311PacketSerializer()));
+            return new MqttClient(options, new MqttChannelCommunicationAdapter(GetMqttCommunicationChannel(options), new MqttPacketSerializer()));
+        }
+
+        private static IMqttCommunicationChannel GetMqttCommunicationChannel(MqttClientOptions options)
+        {
+            switch (options.ConnectionType)
+            {
+                case MqttConnectionType.Tcp:
+                    return new MqttTcpChannel();
+                case MqttConnectionType.Ws:
+                    return new MqttWebSocketChannel();
+
+                default:
+                    throw new NotSupportedException();
+            }
         }
     }
 }

Frameworks/MQTTnet.UniversalWindows/MqttServerFactory.cs

@@ -6,7 +6,7 @@ using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttServerFactory
+    public class MqttServerFactory : IMqttServerFactory
     {
         public IMqttServer CreateMqttServer(MqttServerOptions options)
         {

Frameworks/MQTTnet.UniversalWindows/Properties/AssemblyInfo.cs

@@ -10,5 +10,5 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 [assembly: ComVisible(false)]
-[assembly: AssemblyVersion("2.1.5.1")]
-[assembly: AssemblyFileVersion("2.1.5.1")]
+[assembly: AssemblyVersion("2.3.1.0")]
+[assembly: AssemblyFileVersion("2.3.1.0")]

MQTTnet.Core/Adapter/IMqttCommunicationAdapter.cs

@@ -1,18 +1,23 @@
 using System;
+using System.Collections.Generic;
+using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Packets;
+using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Adapter
 {
     public interface IMqttCommunicationAdapter
     {
-        Task ConnectAsync(MqttClientOptions options, TimeSpan timeout);
+        IMqttPacketSerializer PacketSerializer { get; }
 
-        Task DisconnectAsync();
+        Task ConnectAsync(TimeSpan timeout, MqttClientOptions options);
 
-        Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout);
+        Task DisconnectAsync(TimeSpan timeout);
 
-        Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout);
+        Task SendPacketsAsync(TimeSpan timeout, CancellationToken cancellationToken, IEnumerable<MqttBasePacket> packets);
+
+        Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout, CancellationToken cancellationToken);
     }
 }

MQTTnet.Core/Adapter/MqttChannelCommunicationAdapter.cs

@@ -1,9 +1,13 @@
 using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Exceptions;
+using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Serializer;
 
@@ -11,78 +15,180 @@ namespace MQTTnet.Core.Adapter
 {
     public class MqttChannelCommunicationAdapter : IMqttCommunicationAdapter
     {
-        private readonly IMqttPacketSerializer _serializer;
         private readonly IMqttCommunicationChannel _channel;
+        private readonly SemaphoreSlim _semaphore = new SemaphoreSlim(1, 1);
 
         public MqttChannelCommunicationAdapter(IMqttCommunicationChannel channel, IMqttPacketSerializer serializer)
         {
             _channel = channel ?? throw new ArgumentNullException(nameof(channel));
-            _serializer = serializer ?? throw new ArgumentNullException(nameof(serializer));
+            PacketSerializer = serializer ?? throw new ArgumentNullException(nameof(serializer));
         }
 
-        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
-        {
-            var task = _channel.ConnectAsync(options);
-            if (await Task.WhenAny(Task.Delay(timeout), task) != task)
-            {
-                throw new MqttCommunicationTimedOutException();
-            }
-        }
+        public IMqttPacketSerializer PacketSerializer { get; }
 
-        public async Task DisconnectAsync()
+        public async Task ConnectAsync(TimeSpan timeout, MqttClientOptions options)
         {
-            await _channel.DisconnectAsync();
-        }
-
-        public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
-        {
-            MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), $"TX >>> {packet} [Timeout={timeout}]");
-
-            bool hasTimeout;
             try
             {
-                var task = _serializer.SerializeAsync(packet, _channel);
-                hasTimeout = await Task.WhenAny(Task.Delay(timeout), task) != task;
+                await _channel.ConnectAsync(options).TimeoutAfter(timeout).ConfigureAwait(false);
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
             }
             catch (Exception exception)
             {
                 throw new MqttCommunicationException(exception);
             }
+        }
 
-            if (hasTimeout)
+        public async Task DisconnectAsync(TimeSpan timeout)
+        {
+            try
             {
-                throw new MqttCommunicationTimedOutException();
+                await _channel.DisconnectAsync().TimeoutAfter(timeout).ConfigureAwait(false);
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
             }
         }
 
-        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
+        public async Task SendPacketsAsync(TimeSpan timeout, CancellationToken cancellationToken, IEnumerable<MqttBasePacket> packets)
         {
-            MqttBasePacket packet;
-            if (timeout > TimeSpan.Zero)
-            {
-                var workerTask = _serializer.DeserializeAsync(_channel);
-                var timeoutTask = Task.Delay(timeout);
-                var hasTimeout = Task.WhenAny(timeoutTask, workerTask) == timeoutTask;
+            await _semaphore.WaitAsync(cancellationToken);
 
-                if (hasTimeout)
+            try
+            {
+                foreach (var packet in packets)
                 {
-                    throw new MqttCommunicationTimedOutException();
+                    if (packet == null)
+                    {
+                        continue;
+                    }
+
+                    MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), $"TX >>> {0} [Timeout={1}]", packet, timeout);
+
+                    var writeBuffer = PacketSerializer.Serialize(packet);
+                    await _channel.SendStream.WriteAsync(writeBuffer, 0, writeBuffer.Length, cancellationToken).ConfigureAwait(false);
                 }
 
-                packet = workerTask.Result;
+                if (timeout > TimeSpan.Zero)
+                {
+                    await _channel.SendStream.FlushAsync(cancellationToken).TimeoutAfter(timeout).ConfigureAwait(false);
+                }
+                else
+                {
+                    await _channel.SendStream.FlushAsync(cancellationToken).ConfigureAwait(false);
+                }
             }
-            else
+            catch (TaskCanceledException)
             {
-                packet = await _serializer.DeserializeAsync(_channel);
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+            finally
+            {
+                _semaphore.Release();
+            }
+        }
+
+        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout, CancellationToken cancellationToken)
+        {
+            try
+            {
+                ReceivedMqttPacket receivedMqttPacket;
+                if (timeout > TimeSpan.Zero)
+                {
+                    receivedMqttPacket = await ReceiveAsync(_channel.RawReceiveStream, cancellationToken).TimeoutAfter(timeout).ConfigureAwait(false);
+                }
+                else
+                {
+                    receivedMqttPacket = await ReceiveAsync(_channel.ReceiveStream, cancellationToken).ConfigureAwait(false);
+                }
+
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    throw new TaskCanceledException();
+                }
+
+                var packet = PacketSerializer.Deserialize(receivedMqttPacket);
+                if (packet == null)
+                {
+                    throw new MqttProtocolViolationException("Received malformed packet.");
+                }
+
+                MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), "RX <<< {0}", packet);
+                return packet;
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+        }
+
+        private static async Task<ReceivedMqttPacket> ReceiveAsync(Stream stream, CancellationToken cancellationToken)
+        {
+            var header = MqttPacketReader.ReadHeaderFromSource(stream, cancellationToken);
+
+            if (header.BodyLength == 0)
+            {
+                return new ReceivedMqttPacket(header, new MemoryStream(0));
             }
 
-            if (packet == null)
-            {
-                throw new MqttProtocolViolationException("Received malformed packet.");
-            }
+            var body = new byte[header.BodyLength];
 
-            MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), $"RX <<< {packet}");
-            return packet;
+            var offset = 0;
+            do
+            {
+                var readBytesCount = await stream.ReadAsync(body, offset, body.Length - offset, cancellationToken).ConfigureAwait(false);
+                offset += readBytesCount;
+            } while (offset < header.BodyLength);
+
+            return new ReceivedMqttPacket(header, new MemoryStream(body, 0, body.Length));
         }
     }
-}
+}

MQTTnet.Core/Adapter/MqttCommunicationAdapterExtensions.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Adapter
+{
+    public static class MqttCommunicationAdapterExtensions
+    {
+        public static Task SendPacketsAsync(this IMqttCommunicationAdapter adapter, TimeSpan timeout, CancellationToken cancellationToken, params MqttBasePacket[] packets)
+        {
+            return adapter.SendPacketsAsync(timeout, cancellationToken, packets);
+        }
+    }
+}

MQTTnet.Core/Adapter/MqttConnectingFailedException.cs

@@ -5,7 +5,7 @@ namespace MQTTnet.Core.Adapter
 {
     public class MqttConnectingFailedException : MqttCommunicationException
     {
-        public MqttConnectingFailedException(MqttConnectReturnCode returnCode) 
+        public MqttConnectingFailedException(MqttConnectReturnCode returnCode)
             : base($"Connecting with MQTT server failed ({returnCode}).")
         {
             ReturnCode = returnCode;

MQTTnet.Core/Adapter/ReceivedMqttPacket.cs

@@ -0,0 +1,19 @@
+using System;
+using System.IO;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Adapter
+{
+    public class ReceivedMqttPacket
+    {
+        public ReceivedMqttPacket(MqttPacketHeader header, MemoryStream body)
+        {
+            Header = header ?? throw new ArgumentNullException(nameof(header));
+            Body = body ?? throw new ArgumentNullException(nameof(body));
+        }
+
+        public MqttPacketHeader Header { get; }
+
+        public MemoryStream Body { get; }
+    }
+}

MQTTnet.Core/Channel/IMqttCommunicationChannel.cs

@@ -1,16 +1,16 @@
 using System.Threading.Tasks;
 using MQTTnet.Core.Client;
+using System.IO;
 
 namespace MQTTnet.Core.Channel
 {
     public interface IMqttCommunicationChannel
     {
+        Stream SendStream { get; }
+        Stream ReceiveStream { get; }
+        Stream RawReceiveStream { get; }
+
         Task ConnectAsync(MqttClientOptions options);
-
         Task DisconnectAsync();
-
-        Task WriteAsync(byte[] buffer);
-
-        Task ReadAsync(byte[] buffer);
     }
 }

MQTTnet.Core/Client/IMqttClient.cs

@@ -15,10 +15,10 @@ namespace MQTTnet.Core.Client
 
         Task ConnectAsync(MqttApplicationMessage willApplicationMessage = null);
         Task DisconnectAsync();
-        Task PublishAsync(MqttApplicationMessage applicationMessage);
-        Task<IList<MqttSubscribeResult>> SubscribeAsync(IList<TopicFilter> topicFilters);
-        Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters);
-        Task Unsubscribe(IList<string> topicFilters);
-        Task Unsubscribe(params string[] topicFilters);
+
+        Task<IList<MqttSubscribeResult>> SubscribeAsync(IEnumerable<TopicFilter> topicFilters);
+        Task UnsubscribeAsync(IEnumerable<string> topicFilters);
+
+        Task PublishAsync(IEnumerable<MqttApplicationMessage> applicationMessages);
     }
 }

MQTTnet.Core/Client/IMqttClientFactory.cs

@@ -0,0 +1,7 @@
+namespace MQTTnet.Core.Client
+{
+    public interface IMqttClientFactory
+    {
+        IMqttClient CreateMqttClient(MqttClientOptions options);
+    }
+}

MQTTnet.Core/Client/MqttClient.cs

@@ -15,11 +15,11 @@ namespace MQTTnet.Core.Client
     public class MqttClient : IMqttClient
     {
         private readonly HashSet<ushort> _unacknowledgedPublishPackets = new HashSet<ushort>();
-
         private readonly MqttPacketDispatcher _packetDispatcher = new MqttPacketDispatcher();
         private readonly MqttClientOptions _options;
         private readonly IMqttCommunicationAdapter _adapter;
 
+        private bool _isReceivingPackets;
         private int _latestPacketIdentifier;
         private CancellationTokenSource _cancellationTokenSource;
 
@@ -27,25 +27,151 @@ namespace MQTTnet.Core.Client
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
             _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
+
+            _adapter.PacketSerializer.ProtocolVersion = options.ProtocolVersion;
         }
 
         public event EventHandler Connected;
-
         public event EventHandler Disconnected;
-
         public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
 
-        public bool IsConnected { get; private set; }
+        public bool IsConnected => _cancellationTokenSource != null && !_cancellationTokenSource.IsCancellationRequested;
 
         public async Task ConnectAsync(MqttApplicationMessage willApplicationMessage = null)
         {
-            MqttTrace.Verbose(nameof(MqttClient), "Trying to connect.");
+            ThrowIfConnected("It is not allowed to connect with a server after the connection is established.");
 
-            if (IsConnected)
+            try
             {
-                throw new MqttProtocolViolationException("It is not allowed to connect with a server after the connection is established.");
+                _cancellationTokenSource = new CancellationTokenSource();
+                _latestPacketIdentifier = 0;
+                _packetDispatcher.Reset();
+
+                MqttTrace.Verbose(nameof(MqttClient), "Trying to connect with server.");
+                await _adapter.ConnectAsync(_options.DefaultCommunicationTimeout, _options).ConfigureAwait(false);
+                MqttTrace.Verbose(nameof(MqttClient), "Connection with server established.");
+
+                await SetupIncomingPacketProcessingAsync();
+                await AuthenticateAsync(willApplicationMessage);
+
+                MqttTrace.Verbose(nameof(MqttClient), "MQTT connection with server established.");
+
+                if (_options.KeepAlivePeriod != TimeSpan.Zero)
+                {
+                    StartSendKeepAliveMessages(_cancellationTokenSource.Token);
+                }
+
+                Connected?.Invoke(this, EventArgs.Empty);
+            }
+            catch (Exception)
+            {
+                await DisconnectInternalAsync().ConfigureAwait(false);
+                throw;
+            }
+        }
+
+        public async Task DisconnectAsync()
+        {
+            if (!IsConnected)
+            {
+                return;
             }
 
+            try
+            {
+                await SendAsync(new MqttDisconnectPacket()).ConfigureAwait(false);
+            }
+            finally
+            {
+                await DisconnectInternalAsync().ConfigureAwait(false);
+            }
+        }
+
+        public async Task<IList<MqttSubscribeResult>> SubscribeAsync(IEnumerable<TopicFilter> topicFilters)
+        {
+            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
+
+            ThrowIfNotConnected();
+
+            var subscribePacket = new MqttSubscribePacket
+            {
+                PacketIdentifier = GetNewPacketIdentifier(),
+                TopicFilters = topicFilters.ToList()
+            };
+
+            var response = await SendAndReceiveAsync<MqttSubAckPacket>(subscribePacket).ConfigureAwait(false);
+
+            if (response.SubscribeReturnCodes.Count != subscribePacket.TopicFilters.Count)
+            {
+                throw new MqttProtocolViolationException("The return codes are not matching the topic filters [MQTT-3.9.3-1].");
+            }
+
+            return subscribePacket.TopicFilters.Select((t, i) => new MqttSubscribeResult(t, response.SubscribeReturnCodes[i])).ToList();
+        }
+
+        public async Task UnsubscribeAsync(IEnumerable<string> topicFilters)
+        {
+            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
+
+            ThrowIfNotConnected();
+
+            var unsubscribePacket = new MqttUnsubscribePacket
+            {
+                PacketIdentifier = GetNewPacketIdentifier(),
+                TopicFilters = topicFilters.ToList()
+            };
+
+            await SendAndReceiveAsync<MqttUnsubAckPacket>(unsubscribePacket);
+        }
+
+        public async Task PublishAsync(IEnumerable<MqttApplicationMessage> applicationMessages)
+        {
+            ThrowIfNotConnected();
+
+            var publishPackets = applicationMessages.Select(m => m.ToPublishPacket());
+
+            foreach (var qosGroup in publishPackets.GroupBy(p => p.QualityOfServiceLevel))
+            {
+                var qosPackets = qosGroup.ToArray();
+                switch (qosGroup.Key)
+                {
+                    case MqttQualityOfServiceLevel.AtMostOnce:
+                        {
+                            // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
+                            await _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, qosPackets);
+                            break;
+                        }
+                    case MqttQualityOfServiceLevel.AtLeastOnce:
+                        {
+                            foreach (var publishPacket in qosPackets)
+                            {
+                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                                await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
+                            }
+
+                            break;
+                        }
+                    case MqttQualityOfServiceLevel.ExactlyOnce:
+                        {
+                            foreach (var publishPacket in qosPackets)
+                            {
+                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket).ConfigureAwait(false);
+                                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>()).ConfigureAwait(false);
+                            }
+
+                            break;
+                        }
+                    default:
+                        {
+                            throw new InvalidOperationException();
+                        }
+                }
+            }
+        }
+
+        private async Task AuthenticateAsync(MqttApplicationMessage willApplicationMessage)
+        {
             var connectPacket = new MqttConnectPacket
             {
                 ClientId = _options.ClientId,
@@ -56,115 +182,28 @@ namespace MQTTnet.Core.Client
                 WillMessage = willApplicationMessage
             };
 
-            await _adapter.ConnectAsync(_options, _options.DefaultCommunicationTimeout);
-            MqttTrace.Verbose(nameof(MqttClient), "Connection with server established.");
-
-            _cancellationTokenSource = new CancellationTokenSource();
-            _latestPacketIdentifier = 0;
-            _packetDispatcher.Reset();
-            IsConnected = true;
-
-#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            Task.Run(() => ReceivePackets(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
-#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-
-            var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket);
+            var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket).ConfigureAwait(false);
             if (response.ConnectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
             {
-                await DisconnectAsync();
                 throw new MqttConnectingFailedException(response.ConnectReturnCode);
             }
+        }
+
+        private async Task SetupIncomingPacketProcessingAsync()
+        {
+            _isReceivingPackets = false;
 
-            if (_options.KeepAlivePeriod != TimeSpan.Zero)
-            {
 #pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-                Task.Run(() => SendKeepAliveMessagesAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            Task.Factory.StartNew(
+                () => ReceivePackets(_cancellationTokenSource.Token),
+                _cancellationTokenSource.Token,
+                TaskCreationOptions.LongRunning,
+                TaskScheduler.Default).ConfigureAwait(false);
 #pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            }
 
-            Connected?.Invoke(this, EventArgs.Empty);
-        }
-
-        public async Task DisconnectAsync()
-        {
-            await SendAsync(new MqttDisconnectPacket());
-            await DisconnectInternalAsync();
-        }
-
-        public Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters)
-        {
-            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
-
-            return SubscribeAsync(topicFilters.ToList());
-        }
-
-        public async Task<IList<MqttSubscribeResult>> SubscribeAsync(IList<TopicFilter> topicFilters)
-        {
-            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
-            if (!topicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.8.3-3].");
-
-            ThrowIfNotConnected();
-
-            var subscribePacket = new MqttSubscribePacket
+            while (!_isReceivingPackets && _cancellationTokenSource != null && !_cancellationTokenSource.IsCancellationRequested)
             {
-                PacketIdentifier = GetNewPacketIdentifier(),
-                TopicFilters = topicFilters
-            };
-
-            var response = await SendAndReceiveAsync<MqttSubAckPacket>(subscribePacket);
-
-            if (response.SubscribeReturnCodes.Count != topicFilters.Count)
-            {
-                throw new MqttProtocolViolationException("The return codes are not matching the topic filters [MQTT-3.9.3-1].");
-            }
-
-            return topicFilters.Select((t, i) => new MqttSubscribeResult(t, response.SubscribeReturnCodes[i])).ToList();
-        }
-
-        public Task Unsubscribe(params string[] topicFilters)
-        {
-            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
-
-            return Unsubscribe(topicFilters.ToList());
-        }
-
-        public async Task Unsubscribe(IList<string> topicFilters)
-        {
-            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
-            if (!topicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.10.3-2].");
-            ThrowIfNotConnected();
-
-            var unsubscribePacket = new MqttUnsubscribePacket
-            {
-                PacketIdentifier = GetNewPacketIdentifier(),
-                TopicFilters = topicFilters
-            };
-
-            await SendAndReceiveAsync<MqttUnsubAckPacket>(unsubscribePacket);
-        }
-
-        public async Task PublishAsync(MqttApplicationMessage applicationMessage)
-        {
-            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
-            ThrowIfNotConnected();
-
-            var publishPacket = applicationMessage.ToPublishPacket();
-
-            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
-            {
-                // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
-                await SendAsync(publishPacket);
-            }
-            else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
-            {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
-            }
-            else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
-            {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket);
-                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>());
+                await Task.Delay(TimeSpan.FromMilliseconds(100));
             }
         }
 
@@ -173,86 +212,102 @@ namespace MQTTnet.Core.Client
             if (!IsConnected) throw new MqttCommunicationException("The client is not connected.");
         }
 
+        private void ThrowIfConnected(string message)
+        {
+            if (IsConnected) throw new MqttProtocolViolationException(message);
+        }
+
         private async Task DisconnectInternalAsync()
         {
+            var cts = _cancellationTokenSource;
+            if (cts == null || cts.IsCancellationRequested)
+            {
+                return;
+            }
+
+            cts.Cancel(false);
+            cts.Dispose();
+            _cancellationTokenSource = null;
+
             try
             {
-                await _adapter.DisconnectAsync();
+                await _adapter.DisconnectAsync(_options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                MqttTrace.Information(nameof(MqttClient), "Disconnected from adapter.");
             }
-            catch
+            catch (Exception exception)
             {
+                MqttTrace.Warning(nameof(MqttClient), exception, "Error while disconnecting from adapter.");
             }
             finally
             {
-                _cancellationTokenSource?.Cancel(false);
-                _cancellationTokenSource?.Dispose();
-                _cancellationTokenSource = null;
-
-                IsConnected = false;
                 Disconnected?.Invoke(this, EventArgs.Empty);
             }
         }
 
-        private Task ProcessReceivedPacketAsync(MqttBasePacket mqttPacket)
+        private async Task ProcessReceivedPacketAsync(MqttBasePacket packet)
         {
             try
             {
-                if (mqttPacket is MqttPingReqPacket)
+                MqttTrace.Information(nameof(MqttClient), "Received <<< {0}", packet);
+
+                if (packet is MqttPingReqPacket)
                 {
-                    return SendAsync(new MqttPingRespPacket());
+                    await SendAsync(new MqttPingRespPacket());
+                    return;
                 }
 
-                if (mqttPacket is MqttDisconnectPacket)
+                if (packet is MqttDisconnectPacket)
                 {
-                    return DisconnectAsync();
+                    await DisconnectAsync();
+                    return;
                 }
 
-                if (mqttPacket is MqttPublishPacket publishPacket)
+                if (packet is MqttPublishPacket publishPacket)
                 {
-                    return ProcessReceivedPublishPacket(publishPacket);
+                    await ProcessReceivedPublishPacket(publishPacket);
+                    return;
                 }
 
-                if (mqttPacket is MqttPubRelPacket pubRelPacket)
+                if (packet is MqttPubRelPacket pubRelPacket)
                 {
-                    return ProcessReceivedPubRelPacket(pubRelPacket);
+                    await ProcessReceivedPubRelPacket(pubRelPacket);
+                    return;
                 }
 
-                _packetDispatcher.Dispatch(mqttPacket);
+                _packetDispatcher.Dispatch(packet);
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClient), exception, "Error while processing received packet.");
+                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while processing received packet.");
             }
-
-            return Task.FromResult(0);
         }
 
         private void FireApplicationMessageReceivedEvent(MqttPublishPacket publishPacket)
         {
-            var applicationMessage = publishPacket.ToApplicationMessage();
-
             try
             {
+                var applicationMessage = publishPacket.ToApplicationMessage();
                 ApplicationMessageReceived?.Invoke(this, new MqttApplicationMessageReceivedEventArgs(applicationMessage));
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while handling application message.");    
+                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while handling application message.");
             }
         }
 
-        private Task ProcessReceivedPublishPacket(MqttPublishPacket publishPacket)
+        private async Task ProcessReceivedPublishPacket(MqttPublishPacket publishPacket)
         {
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
-                return Task.FromResult(0);
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
-                return SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                await SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
@@ -264,53 +319,33 @@ namespace MQTTnet.Core.Client
                 }
 
                 FireApplicationMessageReceivedEvent(publishPacket);
-                return SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                await SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             throw new MqttCommunicationException("Received a not supported QoS level.");
         }
 
-        private async Task ProcessReceivedPubRelPacket(MqttPubRelPacket pubRelPacket)
+        private Task ProcessReceivedPubRelPacket(MqttPubRelPacket pubRelPacket)
         {
             lock (_unacknowledgedPublishPackets)
             {
                 _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
-            
-            await SendAsync(pubRelPacket.CreateResponse<MqttPubCompPacket>());
+
+            return SendAsync(pubRelPacket.CreateResponse<MqttPubCompPacket>());
         }
 
         private Task SendAsync(MqttBasePacket packet)
         {
-            return _adapter.SendPacketAsync(packet, _options.DefaultCommunicationTimeout);
+            return _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, packet);
         }
 
         private async Task<TResponsePacket> SendAndReceiveAsync<TResponsePacket>(MqttBasePacket requestPacket) where TResponsePacket : MqttBasePacket
         {
-            bool ResponsePacketSelector(MqttBasePacket p)
-            {
-                var p1 = p as TResponsePacket;
-                if (p1 == null)
-                {
-                    return false;
-                }
-
-                var pi1 = requestPacket as IMqttPacketWithIdentifier;
-                var pi2 = p as IMqttPacketWithIdentifier;
-
-                if (pi1 != null && pi2 != null)
-                {
-                    if (pi1.PacketIdentifier != pi2.PacketIdentifier)
-                    {
-                        return false;
-                    }
-                }
-
-                return true;
-            }
-
-            await _adapter.SendPacketAsync(requestPacket, _options.DefaultCommunicationTimeout);
-            return (TResponsePacket)await _packetDispatcher.WaitForPacketAsync(ResponsePacketSelector, _options.DefaultCommunicationTimeout);
+            var packetAwaiter = _packetDispatcher.WaitForPacketAsync(requestPacket, typeof(TResponsePacket), _options.DefaultCommunicationTimeout);
+            await _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, requestPacket).ConfigureAwait(false);
+            return (TResponsePacket)await packetAwaiter.ConfigureAwait(false);
         }
 
         private ushort GetNewPacketIdentifier()
@@ -326,53 +361,94 @@ namespace MQTTnet.Core.Client
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
-                    await Task.Delay(_options.KeepAlivePeriod, cancellationToken);
-                    await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket());
+                    await Task.Delay(_options.KeepAlivePeriod, cancellationToken).ConfigureAwait(false);
+                    if (cancellationToken.IsCancellationRequested)
+                    {
+                        return;
+                    }
+
+                    await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket()).ConfigureAwait(false);
                 }
             }
+            catch (TaskCanceledException)
+            {
+            }
             catch (MqttCommunicationException exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication error while receiving packets.");
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication exception while sending/receiving keep alive packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             catch (Exception exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "Error while sending/receiving keep alive packets.");
+                MqttTrace.Warning(nameof(MqttClient), exception, "Unhandled exception while sending/receiving keep alive packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             finally
             {
                 MqttTrace.Information(nameof(MqttClient), "Stopped sending keep alive packets.");
-                await DisconnectInternalAsync();
             }
         }
 
         private async Task ReceivePackets(CancellationToken cancellationToken)
         {
             MqttTrace.Information(nameof(MqttClient), "Start receiving packets.");
+
             try
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
-                    var mqttPacket = await _adapter.ReceivePacketAsync(TimeSpan.Zero);
-                    MqttTrace.Information(nameof(MqttClient), $"Received <<< {mqttPacket}");
+                    _isReceivingPackets = true;
 
-#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-                    Task.Run(() => ProcessReceivedPacketAsync(mqttPacket), cancellationToken);
-#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+                    var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
+                    if (cancellationToken.IsCancellationRequested)
+                    {
+                        return;
+                    }
+
+                    StartProcessReceivedPacket(packet, cancellationToken);
                 }
             }
+            catch (TaskCanceledException)
+            {
+            }
             catch (MqttCommunicationException exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication error while receiving packets.");
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication exception while receiving packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClient), exception, "Error while receiving packets.");
+                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while receiving packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             finally
             {
                 MqttTrace.Information(nameof(MqttClient), "Stopped receiving packets.");
-                await DisconnectInternalAsync();
             }
         }
+
+        private void StartProcessReceivedPacket(MqttBasePacket packet, CancellationToken cancellationToken)
+        {
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Run(() => ProcessReceivedPacketAsync(packet), cancellationToken).ConfigureAwait(false);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+        }
+
+        private void StartSendKeepAliveMessages(CancellationToken cancellationToken)
+        {
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Factory.StartNew(() => SendKeepAliveMessagesAsync(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Default).ConfigureAwait(false);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+        }
     }
 }

MQTTnet.Core/Client/MqttClientExtensions.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Client
+{
+    public static class MqttClientExtensions
+    {
+        public static Task PublishAsync(this IMqttClient client, params MqttApplicationMessage[] applicationMessages)
+        {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+            if (applicationMessages == null) throw new ArgumentNullException(nameof(applicationMessages));
+
+            return client.PublishAsync(applicationMessages);
+        }
+
+        public static Task<IList<MqttSubscribeResult>> SubscribeAsync(this IMqttClient client, params TopicFilter[] topicFilters)
+        {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
+
+            return client.SubscribeAsync(topicFilters.ToList());
+        }
+
+        public static Task UnsubscribeAsync(this IMqttClient client, params string[] topicFilters)
+        {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+            if (topicFilters == null) throw new ArgumentNullException(nameof(topicFilters));
+
+            return client.UnsubscribeAsync(topicFilters.ToList());
+        }
+    }
+}

MQTTnet.Core/Client/MqttClientOptions.cs

@@ -1,4 +1,5 @@
 using System;
+using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Client
 {
@@ -7,8 +8,8 @@ namespace MQTTnet.Core.Client
         public string Server { get; set; }
 
         public int? Port { get; set; }
-        
-        public MqttClientTlsOptions TlsOptions { get; } = new MqttClientTlsOptions();
+
+        public MqttClientTlsOptions TlsOptions { get; set; } = new MqttClientTlsOptions();
 
         public string UserName { get; set; }
 
@@ -21,5 +22,9 @@ namespace MQTTnet.Core.Client
         public TimeSpan KeepAlivePeriod { get; set; } = TimeSpan.FromSeconds(5);
 
         public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(10);
+
+        public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
+
+        public MqttConnectionType ConnectionType { get; set; } = MqttConnectionType.Tcp;
     }
 }

MQTTnet.Core/Client/MqttConnectionType.cs

@@ -0,0 +1,8 @@
+namespace MQTTnet.Core.Client
+{
+    public enum MqttConnectionType
+    {
+        Tcp,
+        Ws
+    }
+}

MQTTnet.Core/Client/MqttPacketAwaiter.cs

@@ -1,16 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using MQTTnet.Core.Packets;
-
-namespace MQTTnet.Core.Client
-{
-    public class MqttPacketAwaiter : TaskCompletionSource<MqttBasePacket>
-    {
-        public MqttPacketAwaiter(Func<MqttBasePacket, bool> packetSelector)
-        {
-            PacketSelector = packetSelector ?? throw new ArgumentNullException(nameof(packetSelector));
-        }
-
-        public Func<MqttBasePacket, bool> PacketSelector { get; }
-    }
-}

MQTTnet.Core/Client/MqttPacketDispatcher.cs

@@ -1,111 +1,96 @@
 using System;
-using System.Collections.Generic;
 using System.Threading.Tasks;
 using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Exceptions;
+using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
+using System.Collections.Concurrent;
 
 namespace MQTTnet.Core.Client
 {
     public class MqttPacketDispatcher
     {
-        private readonly object _syncRoot = new object();
-        private readonly List<MqttBasePacket> _receivedPackets = new List<MqttBasePacket>();
-        private readonly List<MqttPacketAwaiter> _packetAwaiters = new List<MqttPacketAwaiter>();
+        private readonly ConcurrentDictionary<Type, TaskCompletionSource<MqttBasePacket>> _packetByResponseType = new ConcurrentDictionary<Type, TaskCompletionSource<MqttBasePacket>>();
+        private readonly ConcurrentDictionary<Type, ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>> _packetByResponseTypeAndIdentifier = new ConcurrentDictionary<Type, ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>>();
 
-        public async Task<MqttBasePacket> WaitForPacketAsync(Func<MqttBasePacket, bool> selector, TimeSpan timeout)
+        public async Task<MqttBasePacket> WaitForPacketAsync(MqttBasePacket request, Type responseType, TimeSpan timeout)
         {
-            if (selector == null) throw new ArgumentNullException(nameof(selector));
+            if (request == null) throw new ArgumentNullException(nameof(request));
 
-            var packetAwaiter = AddPacketAwaiter(selector);
-            DispatchPendingPackets();
-
-            var hasTimeout = await Task.WhenAny(Task.Delay(timeout), packetAwaiter.Task) != packetAwaiter.Task;
-            RemovePacketAwaiter(packetAwaiter);
-
-            if (hasTimeout)
+            var packetAwaiter = AddPacketAwaiter(request, responseType);
+            try
             {
-                MqttTrace.Warning(nameof(MqttPacketDispatcher), "Timeout while waiting for packet.");
-                throw new MqttCommunicationTimedOutException();
+                return await packetAwaiter.Task.TimeoutAfter(timeout).ConfigureAwait(false);
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                MqttTrace.Warning(nameof(MqttPacketDispatcher), "Timeout while waiting for packet of type '{0}'.", responseType.Name);
+                throw;
+            }
+            finally
+            {
+                RemovePacketAwaiter(request, responseType);
             }
-
-            return packetAwaiter.Task.Result;
         }
 
         public void Dispatch(MqttBasePacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
 
-            var packetDispatched = false;
-            foreach (var packetAwaiter in GetPacketAwaiters())
+            var type = packet.GetType();
+            if (packet is IMqttPacketWithIdentifier withIdentifier)
             {
-                if (packetAwaiter.PacketSelector(packet))
+                if (_packetByResponseTypeAndIdentifier.TryGetValue(type, out var byid))
                 {
-                    packetAwaiter.SetResult(packet);
-                    packetDispatched = true;
-                    break;
+                    if (byid.TryRemove(withIdentifier.PacketIdentifier, out var tcs))
+                    {
+                        tcs.TrySetResult(packet);
+                        return;
+                    }
                 }
             }
+            else if (_packetByResponseType.TryRemove(type, out var tcs))
+            {
+                tcs.TrySetResult(packet);
+                return;
+            }
 
-            lock (_syncRoot)
-            {
-                if (!packetDispatched)
-                {
-                    _receivedPackets.Add(packet);
-                }
-                else
-                {
-                    _receivedPackets.Remove(packet);
-                }
-            }
+            throw new InvalidOperationException($"Packet of type '{type.Name}' not handled or dispatched.");
         }
 
         public void Reset()
         {
-            lock (_syncRoot)
-            {
-                _packetAwaiters.Clear();
-                _receivedPackets.Clear();
-            }
+            _packetByResponseTypeAndIdentifier.Clear();
+            _packetByResponseType.Clear();
         }
 
-        private List<MqttPacketAwaiter> GetPacketAwaiters()
+        private TaskCompletionSource<MqttBasePacket> AddPacketAwaiter(MqttBasePacket request, Type responseType)
         {
-            lock (_packetAwaiters)
+            var tcs = new TaskCompletionSource<MqttBasePacket>();
+
+            if (request is IMqttPacketWithIdentifier requestWithIdentifier)
             {
-                return new List<MqttPacketAwaiter>(_packetAwaiters);
+                var byId = _packetByResponseTypeAndIdentifier.GetOrAdd(responseType, key => new ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>());
+                byId[requestWithIdentifier.PacketIdentifier] = tcs;
             }
+            else
+            {
+                _packetByResponseType[responseType] = tcs;
+            }
+
+            return tcs;
         }
 
-        private MqttPacketAwaiter AddPacketAwaiter(Func<MqttBasePacket, bool> selector)
+        private void RemovePacketAwaiter(MqttBasePacket request, Type responseType)
         {
-            lock (_syncRoot)
+            if (request is IMqttPacketWithIdentifier requestWithIdentifier)
             {
-                var packetAwaiter = new MqttPacketAwaiter(selector);
-                _packetAwaiters.Add(packetAwaiter);
-                return packetAwaiter;
+                var byId = _packetByResponseTypeAndIdentifier.GetOrAdd(responseType, key => new ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>());
+                byId.TryRemove(requestWithIdentifier.PacketIdentifier, out var _);
             }
-        }
-
-        private void RemovePacketAwaiter(MqttPacketAwaiter packetAwaiter)
-        {
-            lock (_syncRoot)
+            else
             {
-                _packetAwaiters.Remove(packetAwaiter);
-            }
-        }
-
-        private void DispatchPendingPackets()
-        {
-            List<MqttBasePacket> receivedPackets;
-            lock (_syncRoot)
-            {
-                receivedPackets = new List<MqttBasePacket>(_receivedPackets);
-            }
-
-            foreach (var pendingPacket in receivedPackets)
-            {
-                Dispatch(pendingPacket);
+                _packetByResponseType.TryRemove(responseType, out var _);
             }
         }
     }

MQTTnet.Core/Diagnostics/MqttTrace.cs

@@ -6,39 +6,58 @@ namespace MQTTnet.Core.Diagnostics
     {
         public static event EventHandler<MqttTraceMessagePublishedEventArgs> TraceMessagePublished;
 
-        public static void Verbose(string source, string message)
+        public static void Verbose(string source, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Verbose, null, message);
+            Publish(source, MqttTraceLevel.Verbose, null, message, parameters);
         }
 
-        public static void Information(string source, string message)
+        public static void Information(string source, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Information, null, message);
+            Publish(source, MqttTraceLevel.Information, null, message, parameters);
         }
 
-        public static void Warning(string source, string message)
+        public static void Warning(string source, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Warning, null, message);
+            Publish(source, MqttTraceLevel.Warning, null, message, parameters);
         }
 
-        public static void Warning(string source, Exception exception, string message)
+        public static void Warning(string source, Exception exception, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Warning, exception, message);
+            Publish(source, MqttTraceLevel.Warning, exception, message, parameters);
         }
 
-        public static void Error(string source, string message)
+        public static void Error(string source, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Error, null, message);
+            Publish(source, MqttTraceLevel.Error, null, message, parameters);
         }
 
-        public static void Error(string source, Exception exception, string message)
+        public static void Error(string source, Exception exception, string message, params object[] parameters)
         {
-            Publish(source, MqttTraceLevel.Error, exception, message);
+            Publish(source, MqttTraceLevel.Error, exception, message, parameters);
         }
 
-        private static void Publish(string source, MqttTraceLevel traceLevel, Exception exception, string message)
+        private static void Publish(string source, MqttTraceLevel traceLevel, Exception exception, string message, params object[] parameters)
         {
-            TraceMessagePublished?.Invoke(null, new MqttTraceMessagePublishedEventArgs(Environment.CurrentManagedThreadId, source, traceLevel, message, exception));
+            var handler = TraceMessagePublished;
+            if (handler == null)
+            {
+                return;
+            }
+
+            if (parameters?.Length > 0)
+            {
+                try
+                {
+                    message = string.Format(message, parameters);
+                }
+                catch (Exception formatException)
+                {
+                    Error(nameof(MqttTrace), formatException, "Error while tracing message: " + message);
+                    return;
+                }
+            }
+
+            handler.Invoke(null, new MqttTraceMessagePublishedEventArgs(Environment.CurrentManagedThreadId, source, traceLevel, message, exception));
         }
     }
 }

MQTTnet.Core/Diagnostics/MqttTraceLevel.cs

@@ -1,6 +1,6 @@
 namespace MQTTnet.Core.Diagnostics
 {
-    public enum  MqttTraceLevel
+    public enum MqttTraceLevel
     {
         Verbose,
         Information,

MQTTnet.Core/Exceptions/MqttCommunicationException.cs

@@ -4,7 +4,7 @@ namespace MQTTnet.Core.Exceptions
 {
     public class MqttCommunicationException : Exception
     {
-        public MqttCommunicationException()
+        protected MqttCommunicationException()
         {
         }
 
@@ -17,5 +17,10 @@ namespace MQTTnet.Core.Exceptions
             : base(message)
         {
         }
+
+        public MqttCommunicationException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
     }
 }

MQTTnet.Core/Exceptions/MqttProtocolViolationException.cs

@@ -4,7 +4,7 @@ namespace MQTTnet.Core.Exceptions
 {
     public sealed class MqttProtocolViolationException : Exception
     {
-        public MqttProtocolViolationException(string message) 
+        public MqttProtocolViolationException(string message)
             : base(message)
         {
         }

MQTTnet.Core/Internal/AsyncAutoResetEvent.cs

@@ -1,32 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-
-namespace MQTTnet.Core.Internal
-{
-    public sealed class AsyncGate
-    {
-        private readonly Queue<TaskCompletionSource<bool>> _waitingTasks = new Queue<TaskCompletionSource<bool>>();
-
-        public Task WaitOneAsync()
-        {
-            var tcs = new TaskCompletionSource<bool>();
-            lock (_waitingTasks)
-            {
-                _waitingTasks.Enqueue(tcs);
-            }
-
-            return tcs.Task;
-        }
-
-        public void Set()
-        {
-            lock (_waitingTasks)
-            {
-                if (_waitingTasks.Count > 0)
-                {
-                    _waitingTasks.Dequeue().SetResult(true);
-                }
-            }
-        }
-    }
-}

MQTTnet.Core/Internal/TaskExtensions.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Exceptions;
+
+namespace MQTTnet.Core.Internal
+{
+    public static class TaskExtensions
+    {
+        public static async Task TimeoutAfter(this Task task, TimeSpan timeout)
+        {
+            using (var cancellationTokenSource = new CancellationTokenSource())
+            {
+                try
+                {
+                    var timeoutTask = Task.Delay(timeout, cancellationTokenSource.Token);
+                    var finishedTask = await Task.WhenAny(timeoutTask, task).ConfigureAwait(false);
+
+                    if (finishedTask == timeoutTask)
+                    {
+                        throw new MqttCommunicationTimedOutException();
+                    }
+
+                    if (task.IsCanceled)
+                    {
+                        throw new TaskCanceledException();
+                    }
+
+                    if (task.IsFaulted)
+                    {
+                        throw new MqttCommunicationException(task.Exception.GetBaseException());
+                    }
+                }
+                finally
+                {
+                    cancellationTokenSource.Cancel();
+                }
+            }
+        }
+
+        public static async Task<TResult> TimeoutAfter<TResult>(this Task<TResult> task, TimeSpan timeout)
+        {
+            using (var cancellationTokenSource = new CancellationTokenSource())
+            {
+                try
+                {
+                    var timeoutTask = Task.Delay(timeout, cancellationTokenSource.Token);
+                    var finishedTask = await Task.WhenAny(timeoutTask, task).ConfigureAwait(false);
+
+                    if (finishedTask == timeoutTask)
+                    {
+                        throw new MqttCommunicationTimedOutException();
+                    }
+
+                    if (task.IsCanceled)
+                    {
+                        throw new TaskCanceledException();
+                    }
+
+                    if (task.IsFaulted)
+                    {
+                        throw new MqttCommunicationException(task.Exception.GetBaseException());
+                    }
+
+                    return task.Result;
+                }
+                finally
+                {
+                    cancellationTokenSource.Cancel();
+                }
+            }
+        }
+    }
+}

MQTTnet.Core/MQTTnet.Core.csproj

@@ -5,6 +5,7 @@
     <AssemblyName>MQTTnet.Core</AssemblyName>
     <RootNamespace>MQTTnet.Core</RootNamespace>
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
+    <DebugType>Full</DebugType>
     <Description></Description>
     <Product></Product>
     <Company></Company>
@@ -16,8 +17,8 @@
     <PackageIconUrl></PackageIconUrl>
     <RepositoryUrl></RepositoryUrl>
     <PackageTags></PackageTags>
-    <FileVersion>2.1.5.1</FileVersion>
-    <AssemblyVersion>2.1.5.1</AssemblyVersion>
+    <FileVersion>2.3.1.0</FileVersion>
+    <AssemblyVersion>2.3.1.0</AssemblyVersion>
     <PackageLicenseUrl></PackageLicenseUrl>
   </PropertyGroup>
 

MQTTnet.Core/MqttApplicationMessageFactory.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Globalization;
+using System.IO;
+using System.Text;
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core
+{
+    public class MqttApplicationMessageFactory
+    {
+        public MqttApplicationMessage CreateApplicationMessage(string topic, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
+        {
+            if (topic == null) throw new ArgumentNullException(nameof(topic));
+
+            return CreateApplicationMessage(topic, new byte[0], qualityOfServiceLevel, retain);
+        }
+
+        public MqttApplicationMessage CreateApplicationMessage(string topic, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
+        {
+            if (topic == null) throw new ArgumentNullException(nameof(topic));
+
+            if (payload == null)
+            {
+                payload = new byte[0];
+            }
+
+            return new MqttApplicationMessage(topic, payload, qualityOfServiceLevel, retain);
+        }
+
+        public MqttApplicationMessage CreateApplicationMessage<TPayload>(string topic, TPayload payload, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
+        {
+            if (topic == null) throw new ArgumentNullException(nameof(topic));
+
+            var payloadString = Convert.ToString(payload, CultureInfo.InvariantCulture);
+            var payloadBuffer = string.IsNullOrEmpty(payloadString) ? new byte[0] : Encoding.UTF8.GetBytes(payloadString);
+
+            return CreateApplicationMessage(topic, payloadBuffer, qualityOfServiceLevel, retain);
+        }
+
+        public MqttApplicationMessage CreateApplicationMessage(string topic, Stream payload, MqttQualityOfServiceLevel qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce, bool retain = false)
+        {
+            if (topic == null) throw new ArgumentNullException(nameof(topic));
+
+            byte[] payloadBuffer;
+            if (payload == null || payload.Length == 0)
+            {
+                payloadBuffer = new byte[0];
+            }
+            else
+            {
+                payloadBuffer = new byte[payload.Length - payload.Position];
+                payload.Read(payloadBuffer, 0, payloadBuffer.Length);
+            }
+
+            return CreateApplicationMessage(topic, payloadBuffer, qualityOfServiceLevel, retain);
+        }
+    }
+}

MQTTnet.Core/Packets/MqttConnAckPacket.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return $"{nameof(MqttConnAckPacket)}: [ConnectReturnCode={ConnectReturnCode}] [IsSessionPresent={IsSessionPresent}]";
+            return nameof(MqttConnAckPacket) + ": [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttConnectPacket.cs

@@ -1,7 +1,11 @@
-namespace MQTTnet.Core.Packets
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Core.Packets
 {
-    public sealed class MqttConnectPacket: MqttBasePacket
+    public sealed class MqttConnectPacket : MqttBasePacket
     {
+        public MqttProtocolVersion ProtocolVersion { get; set; }
+
         public string ClientId { get; set; }
 
         public string Username { get; set; }
@@ -16,7 +20,7 @@
 
         public override string ToString()
         {
-            return $"{nameof(MqttConnectPacket)} [ClientId={ClientId}] [Username={Username}] [Password={Password}] [KeepAlivePeriod={KeepAlivePeriod}] [CleanSession={CleanSession}]";
+            return nameof(MqttConnectPacket) + ": [ClientId=" + ClientId + "] [Username=" + Username + "] [Password=" + Password + "] [KeepAlivePeriod=" + KeepAlivePeriod + "] [CleanSession=" + CleanSession + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttPacketHeader.cs

@@ -0,0 +1,13 @@
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core.Packets
+{
+    public class MqttPacketHeader
+    {
+        public MqttControlPacketType ControlPacketType { get; set; }
+
+        public byte FixedHeader { get; set; }
+
+        public int BodyLength { get; set; }
+    }
+}

MQTTnet.Core/Packets/MqttPublishPacket.cs

@@ -1,4 +1,4 @@
-using System.Text;
+using System;
 using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Packets
@@ -17,8 +17,13 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return
-                $"{nameof(MqttPublishPacket)} [Topic={Topic}] [Payload={Encoding.UTF8.GetString(Payload, 0, Payload.Length)}] [QoSLevel={QualityOfServiceLevel}] [Dup={Dup}] [Retain={Retain}] [PacketIdentifier={PacketIdentifier}]";
+            return nameof(MqttPublishPacket) +
+                ": [Topic=" + Topic + "]" +
+                " [Payload=" + Convert.ToBase64String(Payload) + "]" +
+                " [QoSLevel=" + QualityOfServiceLevel + "]" +
+                " [Dup=" + Dup + "]" +
+                " [Retain=" + Retain + "]" +
+                " [PacketIdentifier=" + PacketIdentifier + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttSubAckPacket.cs

@@ -13,8 +13,7 @@ namespace MQTTnet.Core.Packets
         public override string ToString()
         {
             var subscribeReturnCodesText = string.Join(",", SubscribeReturnCodes.Select(f => f.ToString()));
-            return
-                $"{nameof(MqttSubAckPacket)} [PacketIdentifier={PacketIdentifier}] [SubscribeReturnCodes={subscribeReturnCodesText}]";
+            return nameof(MqttSubAckPacket) + ": [PacketIdentifier=" + PacketIdentifier + "] [SubscribeReturnCodes=" + subscribeReturnCodesText + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttSubscribePacket.cs

@@ -6,14 +6,13 @@ namespace MQTTnet.Core.Packets
     public sealed class MqttSubscribePacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
-        
+
         public IList<TopicFilter> TopicFilters { get; set; } = new List<TopicFilter>();
 
         public override string ToString()
         {
             var topicFiltersText = string.Join(",", TopicFilters.Select(f => $"{f.Topic}@{f.QualityOfServiceLevel}"));
-            return
-                $"{nameof(MqttSubscribePacket)} [PacketIdentifier={PacketIdentifier}] [TopicFilters={topicFiltersText}]";
+            return nameof(MqttSubscribePacket) + ": [PacketIdentifier=" + PacketIdentifier + "] [TopicFilters=" + topicFiltersText + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttUnsubscribe.cs

@@ -5,7 +5,7 @@ namespace MQTTnet.Core.Packets
     public sealed class MqttUnsubscribePacket : MqttBasePacket, IMqttPacketWithIdentifier
     {
         public ushort PacketIdentifier { get; set; }
-        
+
         public IList<string> TopicFilters { get; set; } = new List<string>();
     }
 }

MQTTnet.Core/Serializer/IMqttPacketSerializer.cs

@@ -1,13 +1,14 @@
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Serializer
 {
     public interface IMqttPacketSerializer
     {
-        Task SerializeAsync(MqttBasePacket mqttPacket, IMqttCommunicationChannel destination);
+        MqttProtocolVersion ProtocolVersion { get; set; }
 
-        Task<MqttBasePacket> DeserializeAsync(IMqttCommunicationChannel source);
+        byte[] Serialize(MqttBasePacket mqttPacket);
+
+        MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket);
     }
 }

MQTTnet.Core/Serializer/MqttPacketReader.cs

@@ -1,56 +1,44 @@
 using System;
 using System.IO;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Serializer
 {
-    public sealed class MqttPacketReader : IDisposable
+    public sealed class MqttPacketReader : BinaryReader
     {
-        private readonly MemoryStream _remainingData = new MemoryStream();
-        private readonly IMqttCommunicationChannel _source;
-
-        private int _remainingLength;
-
-        public MqttPacketReader(IMqttCommunicationChannel source)
+        private readonly ReceivedMqttPacket _receivedMqttPacket;
+        
+        public MqttPacketReader(ReceivedMqttPacket receivedMqttPacket)
+            : base(receivedMqttPacket.Body, Encoding.UTF8, true)
         {
-            _source = source ?? throw new ArgumentNullException(nameof(source));
+            _receivedMqttPacket = receivedMqttPacket;
         }
 
-        public MqttControlPacketType ControlPacketType { get; private set; }
+        public bool EndOfRemainingData => BaseStream.Position == _receivedMqttPacket.Header.BodyLength;
 
-        public byte FixedHeader { get; private set; }
-
-        public bool EndOfRemainingData => _remainingData.Position == _remainingData.Length;
-
-        public async Task ReadToEndAsync()
+        public static MqttPacketHeader ReadHeaderFromSource(Stream stream, CancellationToken cancellationToken)
         {
-            await ReadFixedHeaderAsync();
-            await ReadRemainingLengthAsync();
+            var fixedHeader = (byte)stream.ReadByte();
+            var controlPacketType = (MqttControlPacketType)(fixedHeader >> 4);
+            var bodyLength = ReadBodyLengthFromSource(stream, cancellationToken);
 
-            if (_remainingLength == 0)
+            return new MqttPacketHeader
             {
-                return;
-            }
-
-            var buffer = new byte[_remainingLength];
-            await ReadFromSourceAsync(buffer);
-            
-            _remainingData.Write(buffer, 0, buffer.Length);
-            _remainingData.Position = 0;
+                FixedHeader = fixedHeader,
+                ControlPacketType = controlPacketType,
+                BodyLength = bodyLength
+            };
         }
 
-        public async Task<byte> ReadRemainingDataByteAsync()
+        public override ushort ReadUInt16()
         {
-            return (await ReadRemainingDataAsync(1))[0];
-        }
-
-        public async Task<ushort> ReadRemainingDataUShortAsync()
-        {
-            var buffer = await ReadRemainingDataAsync(2);
+            var buffer = ReadBytes(2);
 
             var temp = buffer[0];
             buffer[0] = buffer[1];
@@ -59,32 +47,24 @@ namespace MQTTnet.Core.Serializer
             return BitConverter.ToUInt16(buffer, 0);
         }
 
-        public async Task<string> ReadRemainingDataStringWithLengthPrefixAsync()
+        public string ReadStringWithLengthPrefix()
         {
-            var buffer = await ReadRemainingDataWithLengthPrefixAsync();
+            var buffer = ReadWithLengthPrefix();
             return Encoding.UTF8.GetString(buffer, 0, buffer.Length);
         }
 
-        public async Task<byte[]> ReadRemainingDataWithLengthPrefixAsync()
+        public byte[] ReadWithLengthPrefix()
         {
-            var length = await ReadRemainingDataUShortAsync();
-            return await ReadRemainingDataAsync(length);
+            var length = ReadUInt16();
+            return ReadBytes(length);
         }
 
-        public Task<byte[]> ReadRemainingDataAsync()
+        public byte[] ReadRemainingData()
         {
-            return ReadRemainingDataAsync(_remainingLength - (int)_remainingData.Position);
+            return ReadBytes(_receivedMqttPacket.Header.BodyLength - (int)BaseStream.Position);
         }
 
-        public async Task<byte[]> ReadRemainingDataAsync(int length)
-        {
-            var buffer = new byte[length];
-            await _remainingData.ReadAsync(buffer, 0, buffer.Length);
-
-            return buffer;
-        }
-
-        private async Task ReadRemainingLengthAsync()
+        private static int ReadBodyLengthFromSource(Stream stream, CancellationToken cancellationToken)
         {
             // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
             var multiplier = 1;
@@ -92,49 +72,20 @@ namespace MQTTnet.Core.Serializer
             byte encodedByte;
             do
             {
-                encodedByte = await ReadStreamByteAsync();
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    throw new TaskCanceledException();
+                }
+
+                encodedByte = (byte)stream.ReadByte();
                 value += (encodedByte & 127) * multiplier;
                 multiplier *= 128;
                 if (multiplier > 128 * 128 * 128)
                 {
-                    throw new MqttProtocolViolationException("Remaining length is ivalid.");
+                    throw new MqttProtocolViolationException("Remaining length is invalid.");
                 }
             } while ((encodedByte & 128) != 0);
-
-            _remainingLength = value;
-        }
-
-        private Task ReadFromSourceAsync(byte[] buffer)
-        {
-            try
-            {
-                return _source.ReadAsync(buffer);
-            }
-            catch (Exception exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        private async Task<byte> ReadStreamByteAsync()
-        {
-            var buffer = new byte[1];
-            await ReadFromSourceAsync(buffer);
-            return buffer[0];
-        }
-
-        private async Task ReadFixedHeaderAsync()
-        {
-            FixedHeader = await ReadStreamByteAsync();
-
-            var byteReader = new ByteReader(FixedHeader);
-            byteReader.Read(4);
-            ControlPacketType = (MqttControlPacketType)byteReader.Read(4);
-        }
-
-        public void Dispose()
-        {
-            _remainingData?.Dispose();
+            return value;
         }
     }
 }

MQTTnet.Core/Serializer/MqttPacketSerializer.cs

@@ -0,0 +1,609 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Exceptions;
+using MQTTnet.Core.Packets;
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core.Serializer
+{
+    public sealed class MqttPacketSerializer : IMqttPacketSerializer
+    {
+        private static byte[] ProtocolVersionV311Name { get; } = Encoding.UTF8.GetBytes("MQTT");
+        private static byte[] ProtocolVersionV310Name { get; } = Encoding.UTF8.GetBytes("MQIs");
+
+        public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
+
+        public byte[] Serialize(MqttBasePacket packet)
+        {
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
+
+            using (var stream = new MemoryStream())
+            using (var writer = new MqttPacketWriter(stream))
+            {
+                var header = new List<byte> { SerializePacket(packet, writer) };
+                var body = stream.ToArray();
+                MqttPacketWriter.BuildLengthHeader(body.Length, header);
+                var headerArray = header.ToArray();
+                var writeBuffer = new byte[header.Count + body.Length];
+                Buffer.BlockCopy(headerArray, 0, writeBuffer, 0, headerArray.Length);
+                Buffer.BlockCopy(body, 0, writeBuffer, headerArray.Length, body.Length);
+
+                return writeBuffer;
+            }
+        }
+
+        private byte SerializePacket(MqttBasePacket packet, MqttPacketWriter writer)
+        {
+            if (packet is MqttConnectPacket connectPacket)
+            {
+                return Serialize(connectPacket, writer);
+            }
+
+            if (packet is MqttConnAckPacket connAckPacket)
+            {
+                return Serialize(connAckPacket, writer);
+            }
+
+            if (packet is MqttDisconnectPacket disconnectPacket)
+            {
+                return Serialize(disconnectPacket, writer);
+            }
+
+            if (packet is MqttPingReqPacket pingReqPacket)
+            {
+                return Serialize(pingReqPacket, writer);
+            }
+
+            if (packet is MqttPingRespPacket pingRespPacket)
+            {
+                return Serialize(pingRespPacket, writer);
+            }
+
+            if (packet is MqttPublishPacket publishPacket)
+            {
+                return Serialize(publishPacket, writer);
+            }
+
+            if (packet is MqttPubAckPacket pubAckPacket)
+            {
+                return Serialize(pubAckPacket, writer);
+            }
+
+            if (packet is MqttPubRecPacket pubRecPacket)
+            {
+                return Serialize(pubRecPacket, writer);
+            }
+
+            if (packet is MqttPubRelPacket pubRelPacket)
+            {
+                return Serialize(pubRelPacket, writer);
+            }
+
+            if (packet is MqttPubCompPacket pubCompPacket)
+            {
+                return Serialize(pubCompPacket, writer);
+            }
+
+            if (packet is MqttSubscribePacket subscribePacket)
+            {
+                return Serialize(subscribePacket, writer);
+            }
+
+            if (packet is MqttSubAckPacket subAckPacket)
+            {
+                return Serialize(subAckPacket, writer);
+            }
+
+            if (packet is MqttUnsubscribePacket unsubscribePacket)
+            {
+                return Serialize(unsubscribePacket, writer);
+            }
+
+            if (packet is MqttUnsubAckPacket unsubAckPacket)
+            {
+                return Serialize(unsubAckPacket, writer);
+            }
+
+            throw new MqttProtocolViolationException("Packet type invalid.");
+        }
+
+        public MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket)
+        {
+            if (receivedMqttPacket == null) throw new ArgumentNullException(nameof(receivedMqttPacket));
+
+            using (var reader = new MqttPacketReader(receivedMqttPacket))
+            {
+                return Deserialize(receivedMqttPacket.Header, reader);
+            }
+        }
+
+        private static MqttBasePacket Deserialize(MqttPacketHeader header, MqttPacketReader reader)
+        {
+            switch (header.ControlPacketType)
+            {
+                case MqttControlPacketType.Connect:
+                    {
+                        return DeserializeConnect(reader);
+                    }
+
+                case MqttControlPacketType.ConnAck:
+                    {
+                        return DeserializeConnAck(reader);
+                    }
+
+                case MqttControlPacketType.Disconnect:
+                    {
+                        return new MqttDisconnectPacket();
+                    }
+
+                case MqttControlPacketType.Publish:
+                    {
+                        return DeserializePublish(reader, header);
+                    }
+
+                case MqttControlPacketType.PubAck:
+                    {
+                        return new MqttPubAckPacket
+                        {
+                            PacketIdentifier = reader.ReadUInt16()
+                        };
+                    }
+
+                case MqttControlPacketType.PubRec:
+                    {
+                        return new MqttPubRecPacket
+                        {
+                            PacketIdentifier = reader.ReadUInt16()
+                        };
+                    }
+
+                case MqttControlPacketType.PubRel:
+                    {
+                        return new MqttPubRelPacket
+                        {
+                            PacketIdentifier = reader.ReadUInt16()
+                        };
+                    }
+
+                case MqttControlPacketType.PubComp:
+                    {
+                        return new MqttPubCompPacket
+                        {
+                            PacketIdentifier = reader.ReadUInt16()
+                        };
+                    }
+
+                case MqttControlPacketType.PingReq:
+                    {
+                        return new MqttPingReqPacket();
+                    }
+
+                case MqttControlPacketType.PingResp:
+                    {
+                        return new MqttPingRespPacket();
+                    }
+
+                case MqttControlPacketType.Subscribe:
+                    {
+                        return DeserializeSubscribe(reader);
+                    }
+
+                case MqttControlPacketType.SubAck:
+                    {
+                        return DeserializeSubAck(reader);
+                    }
+
+                case MqttControlPacketType.Unsubscibe:
+                    {
+                        return DeserializeUnsubscribe(reader);
+                    }
+
+                case MqttControlPacketType.UnsubAck:
+                    {
+                        return new MqttUnsubAckPacket
+                        {
+                            PacketIdentifier = reader.ReadUInt16()
+                        };
+                    }
+
+                default:
+                    {
+                        throw new MqttProtocolViolationException(
+                            $"Packet type ({(int)header.ControlPacketType}) not supported.");
+                    }
+            }
+        }
+
+        private static MqttBasePacket DeserializeUnsubscribe(MqttPacketReader reader)
+        {
+            var packet = new MqttUnsubscribePacket
+            {
+                PacketIdentifier = reader.ReadUInt16(),
+            };
+
+            while (!reader.EndOfRemainingData)
+            {
+                packet.TopicFilters.Add(reader.ReadStringWithLengthPrefix());
+            }
+
+            return packet;
+        }
+
+        private static MqttBasePacket DeserializeSubscribe(MqttPacketReader reader)
+        {
+            var packet = new MqttSubscribePacket
+            {
+                PacketIdentifier = reader.ReadUInt16()
+            };
+
+            while (!reader.EndOfRemainingData)
+            {
+                packet.TopicFilters.Add(new TopicFilter(
+                    reader.ReadStringWithLengthPrefix(),
+                    (MqttQualityOfServiceLevel)reader.ReadByte()));
+            }
+
+            return packet;
+        }
+
+        private static MqttBasePacket DeserializePublish(MqttPacketReader reader, MqttPacketHeader mqttPacketHeader)
+        {
+            var fixedHeader = new ByteReader(mqttPacketHeader.FixedHeader);
+            var retain = fixedHeader.Read();
+            var qualityOfServiceLevel = (MqttQualityOfServiceLevel)fixedHeader.Read(2);
+            var dup = fixedHeader.Read();
+
+            var topic = reader.ReadStringWithLengthPrefix();
+
+            ushort packetIdentifier = 0;
+            if (qualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+            {
+                packetIdentifier = reader.ReadUInt16();
+            }
+
+            var packet = new MqttPublishPacket
+            {
+                Retain = retain,
+                QualityOfServiceLevel = qualityOfServiceLevel,
+                Dup = dup,
+                Topic = topic,
+                Payload = reader.ReadRemainingData(),
+                PacketIdentifier = packetIdentifier
+            };
+
+            return packet;
+        }
+
+        private static MqttBasePacket DeserializeConnect(MqttPacketReader reader)
+        {
+            reader.ReadBytes(2); // Skip 2 bytes
+
+            MqttProtocolVersion protocolVersion;
+            var protocolName = reader.ReadBytes(4);
+            if (protocolName.SequenceEqual(ProtocolVersionV310Name))
+            {
+                reader.ReadBytes(2);
+                protocolVersion = MqttProtocolVersion.V310;
+            }
+            else if (protocolName.SequenceEqual(ProtocolVersionV311Name))
+            {
+                protocolVersion = MqttProtocolVersion.V311;
+            }
+            else
+            {
+                throw new MqttProtocolViolationException("Protocol name is not supported.");
+            }
+
+            var protocolLevel = reader.ReadByte();
+            var connectFlags = reader.ReadByte();
+
+            var connectFlagsReader = new ByteReader(connectFlags);
+            connectFlagsReader.Read(); // Reserved.
+
+            var packet = new MqttConnectPacket
+            {
+                ProtocolVersion = protocolVersion,
+                CleanSession = connectFlagsReader.Read()
+            };
+
+            var willFlag = connectFlagsReader.Read();
+            var willQoS = connectFlagsReader.Read(2);
+            var willRetain = connectFlagsReader.Read();
+            var passwordFlag = connectFlagsReader.Read();
+            var usernameFlag = connectFlagsReader.Read();
+
+            packet.KeepAlivePeriod = reader.ReadUInt16();
+            packet.ClientId = reader.ReadStringWithLengthPrefix();
+
+            if (willFlag)
+            {
+                packet.WillMessage = new MqttApplicationMessage(
+                    reader.ReadStringWithLengthPrefix(),
+                    reader.ReadWithLengthPrefix(),
+                    (MqttQualityOfServiceLevel)willQoS,
+                    willRetain);
+            }
+
+            if (usernameFlag)
+            {
+                packet.Username = reader.ReadStringWithLengthPrefix();
+            }
+
+            if (passwordFlag)
+            {
+                packet.Password = reader.ReadStringWithLengthPrefix();
+            }
+
+            ValidateConnectPacket(packet);
+            return packet;
+        }
+
+        private static MqttBasePacket DeserializeSubAck(MqttPacketReader reader)
+        {
+            var packet = new MqttSubAckPacket
+            {
+                PacketIdentifier = reader.ReadUInt16()
+            };
+
+            while (!reader.EndOfRemainingData)
+            {
+                packet.SubscribeReturnCodes.Add((MqttSubscribeReturnCode)reader.ReadByte());
+            }
+
+            return packet;
+        }
+
+        private static MqttBasePacket DeserializeConnAck(MqttPacketReader reader)
+        {
+            var variableHeader1 = reader.ReadByte();
+            var variableHeader2 = reader.ReadByte();
+
+            var packet = new MqttConnAckPacket
+            {
+                IsSessionPresent = new ByteReader(variableHeader1).Read(),
+                ConnectReturnCode = (MqttConnectReturnCode)variableHeader2
+            };
+
+            return packet;
+        }
+
+        private static void ValidateConnectPacket(MqttConnectPacket packet)
+        {
+            if (string.IsNullOrEmpty(packet.ClientId) && !packet.CleanSession)
+            {
+                throw new MqttProtocolViolationException("CleanSession must be set if ClientId is empty [MQTT-3.1.3-7].");
+            }
+        }
+
+        private static void ValidatePublishPacket(MqttPublishPacket packet)
+        {
+            if (packet.QualityOfServiceLevel == 0 && packet.Dup)
+            {
+                throw new MqttProtocolViolationException("Dup flag must be false for QoS 0 packets [MQTT-3.3.1-2].");
+            }
+        }
+
+        private byte Serialize(MqttConnectPacket packet, MqttPacketWriter writer)
+        {
+            ValidateConnectPacket(packet);
+
+            // Write variable header
+            writer.Write(0x00, 0x04); // 3.1.2.1 Protocol Name
+            if (ProtocolVersion == MqttProtocolVersion.V311)
+            {
+                writer.Write(ProtocolVersionV311Name);
+                writer.Write(0x04); // 3.1.2.2 Protocol Level (4)
+            }
+            else
+            {
+                writer.Write(ProtocolVersionV310Name);
+                writer.Write(0x64, 0x70, 0x03); // Protocol Level (0x03)
+            }
+
+            var connectFlags = new ByteWriter(); // 3.1.2.3 Connect Flags
+            connectFlags.Write(false); // Reserved
+            connectFlags.Write(packet.CleanSession);
+            connectFlags.Write(packet.WillMessage != null);
+
+            if (packet.WillMessage != null)
+            {
+                connectFlags.Write((int)packet.WillMessage.QualityOfServiceLevel, 2);
+                connectFlags.Write(packet.WillMessage.Retain);
+            }
+            else
+            {
+                connectFlags.Write(0, 2);
+                connectFlags.Write(false);
+            }
+
+            connectFlags.Write(packet.Password != null);
+            connectFlags.Write(packet.Username != null);
+
+            writer.Write(connectFlags);
+            writer.Write(packet.KeepAlivePeriod);
+            writer.WriteWithLengthPrefix(packet.ClientId);
+
+            if (packet.WillMessage != null)
+            {
+                writer.WriteWithLengthPrefix(packet.WillMessage.Topic);
+                writer.WriteWithLengthPrefix(packet.WillMessage.Payload);
+            }
+
+            if (packet.Username != null)
+            {
+                writer.WriteWithLengthPrefix(packet.Username);
+            }
+
+            if (packet.Password != null)
+            {
+                writer.WriteWithLengthPrefix(packet.Password);
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Connect);
+        }
+
+        private byte Serialize(MqttConnAckPacket packet, MqttPacketWriter writer)
+        {
+            var connectAcknowledgeFlags = new ByteWriter();
+
+            if (ProtocolVersion == MqttProtocolVersion.V311)
+            {
+                connectAcknowledgeFlags.Write(packet.IsSessionPresent);
+            }
+
+            writer.Write(connectAcknowledgeFlags);
+            writer.Write((byte)packet.ConnectReturnCode);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.ConnAck);
+        }
+
+        private static byte Serialize(MqttPubRelPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRel, 0x02);
+        }
+
+        private static byte Serialize(MqttDisconnectPacket packet, MqttPacketWriter writer)
+        {
+            return SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, writer);
+        }
+
+        private static byte Serialize(MqttPingReqPacket packet, MqttPacketWriter writer)
+        {
+            return SerializeEmptyPacketAsync(MqttControlPacketType.PingReq, writer);
+        }
+
+        private static byte Serialize(MqttPingRespPacket packet, MqttPacketWriter writer)
+        {
+            return SerializeEmptyPacketAsync(MqttControlPacketType.PingResp, writer);
+        }
+
+        private static byte Serialize(MqttPublishPacket packet, MqttPacketWriter writer)
+        {
+            ValidatePublishPacket(packet);
+
+            writer.WriteWithLengthPrefix(packet.Topic);
+
+            if (packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+            {
+                writer.Write(packet.PacketIdentifier);
+            }
+            else
+            {
+                if (packet.PacketIdentifier > 0)
+                {
+                    throw new MqttProtocolViolationException("Packet identifier must be empty if QoS == 0 [MQTT-2.3.1-5].");
+                }
+            }
+
+            if (packet.Payload?.Length > 0)
+            {
+                writer.Write(packet.Payload);
+            }
+
+            byte fixedHeader = 0;
+
+            if (packet.Retain)
+            {
+                fixedHeader |= 0x01;
+            }
+
+            fixedHeader |= (byte)((byte)packet.QualityOfServiceLevel << 1);
+
+            if (packet.Dup)
+            {
+                fixedHeader |= 0x08;
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Publish, fixedHeader);
+        }
+
+        private static byte Serialize(MqttPubAckPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubAck);
+        }
+
+        private static byte Serialize(MqttPubRecPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRec);
+        }
+
+        private static byte Serialize(MqttPubCompPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubComp);
+        }
+
+        private static byte Serialize(MqttSubscribePacket packet, MqttPacketWriter writer)
+        {
+            if (!packet.TopicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.8.3-3].");
+
+            writer.Write(packet.PacketIdentifier);
+
+            if (packet.TopicFilters?.Count > 0)
+            {
+                foreach (var topicFilter in packet.TopicFilters)
+                {
+                    writer.WriteWithLengthPrefix(topicFilter.Topic);
+                    writer.Write((byte)topicFilter.QualityOfServiceLevel);
+                }
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Subscribe, 0x02);
+        }
+
+        private static byte Serialize(MqttSubAckPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            if (packet.SubscribeReturnCodes?.Any() == true)
+            {
+                foreach (var packetSubscribeReturnCode in packet.SubscribeReturnCodes)
+                {
+                    writer.Write((byte)packetSubscribeReturnCode);
+                }
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.SubAck);
+        }
+
+        private static byte Serialize(MqttUnsubscribePacket packet, MqttPacketWriter writer)
+        {
+            if (!packet.TopicFilters.Any()) throw new MqttProtocolViolationException("At least one topic filter must be set [MQTT-3.10.3-2].");
+
+            writer.Write(packet.PacketIdentifier);
+
+            if (packet.TopicFilters?.Any() == true)
+            {
+                foreach (var topicFilter in packet.TopicFilters)
+                {
+                    writer.WriteWithLengthPrefix(topicFilter);
+                }
+            }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
+        }
+
+        private static byte Serialize(MqttUnsubAckPacket packet, MqttPacketWriter writer)
+        {
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.UnsubAck);
+        }
+
+        private static byte SerializeEmptyPacketAsync(MqttControlPacketType type, MqttPacketWriter writer)
+        {
+            return MqttPacketWriter.BuildFixedHeader(type);
+        }
+    }
+}

MQTTnet.Core/Serializer/MqttPacketWriter.cs

@@ -1,47 +1,46 @@
 using System;
 using System.IO;
 using System.Text;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
 using MQTTnet.Core.Protocol;
+using System.Collections.Generic;
 
 namespace MQTTnet.Core.Serializer
 {
-    public sealed class MqttPacketWriter : IDisposable
+    public sealed class MqttPacketWriter : BinaryWriter
     {
-        private readonly MemoryStream _buffer = new MemoryStream(512);
-
-        public void InjectFixedHeader(MqttControlPacketType packetType, byte flags = 0)
+        public MqttPacketWriter(Stream stream)
+            : base(stream)
         {
-            var fixedHeader = (byte)((byte)packetType << 4);
+        }
+
+        public static byte BuildFixedHeader(MqttControlPacketType packetType, byte flags = 0)
+        {
+            var fixedHeader = (int)packetType << 4;
             fixedHeader |= flags;
-            InjectFixedHeader(fixedHeader);
+            return (byte)fixedHeader;
         }
 
-        public void Write(byte value)
-        {
-            _buffer.WriteByte(value);
-        }
-
-        public void Write(ushort value)
+        public override void Write(ushort value)
         {
             var buffer = BitConverter.GetBytes(value);
-            _buffer.WriteByte(buffer[1]);
-            _buffer.WriteByte(buffer[0]);
+            Write(buffer[1], buffer[0]);
+        }
+
+        public new void Write(params byte[] values)
+        {
+            base.Write(values);
+        }
+
+        public new void Write(byte value)
+        {
+            base.Write(value);
         }
 
         public void Write(ByteWriter value)
         {
             if (value == null) throw new ArgumentNullException(nameof(value));
 
-            _buffer.WriteByte(value.Value);
-        }
-
-        public void Write(params byte[] value)
-        {
-            if (value == null) throw new ArgumentNullException(nameof(value));
-
-            _buffer.Write(value, 0, value.Length);
+            Write(value.Value);
         }
 
         public void WriteWithLengthPrefix(string value)
@@ -57,36 +56,16 @@ namespace MQTTnet.Core.Serializer
             Write(value);
         }
 
-        public Task WriteToAsync(IMqttCommunicationChannel destination)
+        public static void BuildLengthHeader(int length, List<byte> header)
         {
-            if (destination == null) throw new ArgumentNullException(nameof(destination));
-
-            return destination.WriteAsync(_buffer.ToArray());
-        }
-
-        public void Dispose()
-        {
-            _buffer?.Dispose();
-        }
-
-        private void InjectFixedHeader(byte fixedHeader)
-        {
-            if (_buffer.Length == 0)
+            if (length == 0)
             {
-                Write(fixedHeader);
-                Write(0);
+                header.Add(0);
                 return;
             }
 
-            var backupBuffer = _buffer.ToArray();
-            var remainingLength = (int)_buffer.Length;
-
-            _buffer.SetLength(0);
-
-            _buffer.WriteByte(fixedHeader);
-
             // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
-            var x = remainingLength;
+            var x = length;
             do
             {
                 var encodedByte = x % 128;
@@ -96,10 +75,8 @@ namespace MQTTnet.Core.Serializer
                     encodedByte = encodedByte | 128;
                 }
 
-                _buffer.WriteByte((byte)encodedByte);
+                header.Add((byte)encodedByte);
             } while (x > 0);
-
-            _buffer.Write(backupBuffer, 0, backupBuffer.Length);
         }
     }
 }

MQTTnet.Core/Serializer/MqttProtocolVersion.cs

@@ -0,0 +1,8 @@
+namespace MQTTnet.Core.Serializer
+{
+    public enum MqttProtocolVersion
+    {
+        V311,
+        V310
+    }
+}

MQTTnet.Core/Serializer/MqttV311PacketSerializer.cs

@@ -1,598 +0,0 @@
-using System;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
-using MQTTnet.Core.Exceptions;
-using MQTTnet.Core.Packets;
-using MQTTnet.Core.Protocol;
-
-namespace MQTTnet.Core.Serializer
-{
-    public sealed class MqttV311PacketSerializer : IMqttPacketSerializer
-    {
-        private static readonly byte[] MqttV311Prefix = Encoding.UTF8.GetBytes("MQTT");
-
-        public Task SerializeAsync(MqttBasePacket packet, IMqttCommunicationChannel destination)
-        {
-            if (packet == null) throw new ArgumentNullException(nameof(packet));
-            if (destination == null) throw new ArgumentNullException(nameof(destination));
-
-            if (packet is MqttConnectPacket connectPacket)
-            {
-                return SerializeAsync(connectPacket, destination);
-            }
-
-            if (packet is MqttConnAckPacket connAckPacket)
-            {
-                return SerializeAsync(connAckPacket, destination);
-            }
-
-            if (packet is MqttDisconnectPacket disconnectPacket)
-            {
-                return SerializeAsync(disconnectPacket, destination);
-            }
-
-            if (packet is MqttPingReqPacket pingReqPacket)
-            {
-                return SerializeAsync(pingReqPacket, destination);
-            }
-
-            if (packet is MqttPingRespPacket pingRespPacket)
-            {
-                return SerializeAsync(pingRespPacket, destination);
-            }
-
-            if (packet is MqttPublishPacket publishPacket)
-            {
-                return SerializeAsync(publishPacket, destination);
-            }
-
-            if (packet is MqttPubAckPacket pubAckPacket)
-            {
-                return SerializeAsync(pubAckPacket, destination);
-            }
-
-            if (packet is MqttPubRecPacket pubRecPacket)
-            {
-                return SerializeAsync(pubRecPacket, destination);
-            }
-
-            if (packet is MqttPubRelPacket pubRelPacket)
-            {
-                return SerializeAsync(pubRelPacket, destination);
-            }
-
-            if (packet is MqttPubCompPacket pubCompPacket)
-            {
-                return SerializeAsync(pubCompPacket, destination);
-            }
-
-            if (packet is MqttSubscribePacket subscribePacket)
-            {
-                return SerializeAsync(subscribePacket, destination);
-            }
-
-            if (packet is MqttSubAckPacket subAckPacket)
-            {
-                return SerializeAsync(subAckPacket, destination);
-            }
-
-            if (packet is MqttUnsubscribePacket unsubscribePacket)
-            {
-                return SerializeAsync(unsubscribePacket, destination);
-            }
-
-            if (packet is MqttUnsubAckPacket unsubAckPacket)
-            {
-                return SerializeAsync(unsubAckPacket, destination);
-            }
-
-            throw new MqttProtocolViolationException("Packet type invalid.");
-        }
-
-        public async Task<MqttBasePacket> DeserializeAsync(IMqttCommunicationChannel source)
-        {
-            if (source == null) throw new ArgumentNullException(nameof(source));
-
-            using (var mqttPacketReader = new MqttPacketReader(source))
-            {
-                await mqttPacketReader.ReadToEndAsync();
-
-                switch (mqttPacketReader.ControlPacketType)
-                {
-                    case MqttControlPacketType.Connect:
-                        {
-                            return await DeserializeConnectAsync(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.ConnAck:
-                        {
-                            return await DeserializeConnAck(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.Disconnect:
-                        {
-                            return new MqttDisconnectPacket();
-                        }
-
-                    case MqttControlPacketType.Publish:
-                        {
-                            return await DeserializePublishAsync(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.PubAck:
-                        {
-                            return new MqttPubAckPacket
-                            {
-                                PacketIdentifier = await mqttPacketReader.ReadRemainingDataUShortAsync()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubRec:
-                        {
-                            return new MqttPubRecPacket
-                            {
-                                PacketIdentifier = await mqttPacketReader.ReadRemainingDataUShortAsync()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubRel:
-                        {
-                            return new MqttPubRelPacket
-                            {
-                                PacketIdentifier = await mqttPacketReader.ReadRemainingDataUShortAsync()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubComp:
-                        {
-                            return new MqttPubCompPacket
-                            {
-                                PacketIdentifier = await mqttPacketReader.ReadRemainingDataUShortAsync()
-                            };
-                        }
-
-                    case MqttControlPacketType.PingReq:
-                        {
-                            return new MqttPingReqPacket();
-                        }
-
-                    case MqttControlPacketType.PingResp:
-                        {
-                            return new MqttPingRespPacket();
-                        }
-
-                    case MqttControlPacketType.Subscribe:
-                        {
-                            return await DeserializeSubscribeAsync(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.SubAck:
-                        {
-                            return await DeserializeSubAck(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.Unsubscibe:
-                        {
-                            return await DeserializeUnsubscribeAsync(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.UnsubAck:
-                        {
-                            return new MqttUnsubAckPacket
-                            {
-                                PacketIdentifier = await mqttPacketReader.ReadRemainingDataUShortAsync()
-                            };
-                        }
-
-                    default:
-                        {
-                            throw new MqttProtocolViolationException($"Packet type ({(int)mqttPacketReader.ControlPacketType}) not supported.");
-                        }
-                }
-            }
-        }
-
-        private static async Task<MqttBasePacket> DeserializeUnsubscribeAsync(MqttPacketReader reader)
-        {
-            var packet = new MqttUnsubscribePacket
-            {
-                PacketIdentifier = await reader.ReadRemainingDataUShortAsync(),
-            };
-
-            while (!reader.EndOfRemainingData)
-            {
-                packet.TopicFilters.Add(await reader.ReadRemainingDataStringWithLengthPrefixAsync());
-            }
-
-            return packet;
-        }
-
-        private static async Task<MqttBasePacket> DeserializeSubscribeAsync(MqttPacketReader reader)
-        {
-            var packet = new MqttSubscribePacket
-            {
-                PacketIdentifier = await reader.ReadRemainingDataUShortAsync(),
-            };
-
-            while (!reader.EndOfRemainingData)
-            {
-                packet.TopicFilters.Add(new TopicFilter(
-                    await reader.ReadRemainingDataStringWithLengthPrefixAsync(),
-                    (MqttQualityOfServiceLevel)await reader.ReadRemainingDataByteAsync()));
-            }
-
-            return packet;
-        }
-
-        private static async Task<MqttBasePacket> DeserializePublishAsync(MqttPacketReader reader)
-        {
-            var fixedHeader = new ByteReader(reader.FixedHeader);
-            var retain = fixedHeader.Read();
-            var qualityOfServiceLevel = (MqttQualityOfServiceLevel)fixedHeader.Read(2);
-            var dup = fixedHeader.Read();
-
-            var topic = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
-
-            ushort packetIdentifier = 0;
-            if (qualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
-            {
-                packetIdentifier = await reader.ReadRemainingDataUShortAsync();
-            }
-
-            var packet = new MqttPublishPacket
-            {
-                Retain = retain,
-                QualityOfServiceLevel = qualityOfServiceLevel,
-                Dup = dup,
-                Topic = topic,
-                Payload = await reader.ReadRemainingDataAsync(),
-                PacketIdentifier = packetIdentifier
-            };
-
-            return packet;
-        }
-
-        private static async Task<MqttBasePacket> DeserializeConnectAsync(MqttPacketReader reader)
-        {
-            await reader.ReadRemainingDataAsync(2); // Skip 2 bytes
-            
-            var protocolName = await reader.ReadRemainingDataAsync(4);
-
-            if (Encoding.UTF8.GetString(protocolName, 0, protocolName.Length) != "MQTT")
-            {
-                throw new MqttProtocolViolationException("Protocol name is not 'MQTT'.");
-            }
-
-            var protocolLevel = await reader.ReadRemainingDataByteAsync();
-            var connectFlags = await reader.ReadRemainingDataByteAsync();
-
-            var connectFlagsReader = new ByteReader(connectFlags);
-            connectFlagsReader.Read(); // Reserved.
-
-            var packet = new MqttConnectPacket
-            {
-                CleanSession = connectFlagsReader.Read()
-            };
-
-            var willFlag = connectFlagsReader.Read();
-            var willQoS = connectFlagsReader.Read(2);
-            var willRetain = connectFlagsReader.Read();
-            var passwordFlag = connectFlagsReader.Read();
-            var usernameFlag = connectFlagsReader.Read();
-
-            packet.KeepAlivePeriod = await reader.ReadRemainingDataUShortAsync();
-            packet.ClientId = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
-
-            if (willFlag)
-            {
-                packet.WillMessage = new MqttApplicationMessage(
-                    await reader.ReadRemainingDataStringWithLengthPrefixAsync(),
-                    await reader.ReadRemainingDataWithLengthPrefixAsync(),
-                    (MqttQualityOfServiceLevel)willQoS,
-                    willRetain);
-            }
-
-            if (usernameFlag)
-            {
-                packet.Username = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
-            }
-
-            if (passwordFlag)
-            {
-                packet.Password = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
-            }
-
-            ValidateConnectPacket(packet);
-            return packet;
-        }
-
-        private static async Task<MqttBasePacket> DeserializeSubAck(MqttPacketReader reader)
-        {
-            var packet = new MqttSubAckPacket
-            {
-                PacketIdentifier = await reader.ReadRemainingDataUShortAsync()
-            };
-
-            while (!reader.EndOfRemainingData)
-            {
-                packet.SubscribeReturnCodes.Add((MqttSubscribeReturnCode)await reader.ReadRemainingDataByteAsync());
-            }
-
-            return packet;
-        }
-
-        private static async Task<MqttBasePacket> DeserializeConnAck(MqttPacketReader reader)
-        {
-            var variableHeader1 = await reader.ReadRemainingDataByteAsync();
-            var variableHeader2 = await reader.ReadRemainingDataByteAsync();
-
-            var packet = new MqttConnAckPacket
-            {
-                IsSessionPresent = new ByteReader(variableHeader1).Read(),
-                ConnectReturnCode = (MqttConnectReturnCode)variableHeader2
-            };
-
-            return packet;
-        }
-
-        private static void ValidateConnectPacket(MqttConnectPacket packet)
-        {
-            if (string.IsNullOrEmpty(packet.ClientId) && !packet.CleanSession)
-            {
-                throw new MqttProtocolViolationException("CleanSession must be set if ClientId is empty [MQTT-3.1.3-7].");
-            }
-        }
-
-        private static void ValidatePublishPacket(MqttPublishPacket packet)
-        {
-            if (packet.QualityOfServiceLevel == 0 && packet.Dup)
-            {
-                throw new MqttProtocolViolationException("Dup flag must be false for QoS 0 packets [MQTT-3.3.1-2].");
-            }
-        }
-
-        private static Task SerializeAsync(MqttConnectPacket packet, IMqttCommunicationChannel destination)
-        {
-            ValidateConnectPacket(packet);
-
-            using (var output = new MqttPacketWriter())
-            {
-                // Write variable header
-                output.Write(0x00, 0x04); // 3.1.2.1 Protocol Name
-                output.Write(MqttV311Prefix);
-                output.Write(0x04); // 3.1.2.2 Protocol Level
-
-                var connectFlags = new ByteWriter(); // 3.1.2.3 Connect Flags
-                connectFlags.Write(false); // Reserved
-                connectFlags.Write(packet.CleanSession);
-                connectFlags.Write(packet.WillMessage != null);
-
-                if (packet.WillMessage != null)
-                {
-                    connectFlags.Write((int)packet.WillMessage.QualityOfServiceLevel, 2);
-                    connectFlags.Write(packet.WillMessage.Retain);
-                }
-                else
-                {
-                    connectFlags.Write(0, 2);
-                    connectFlags.Write(false);
-                }
-                
-                connectFlags.Write(packet.Password != null);
-                connectFlags.Write(packet.Username != null);
-
-                output.Write(connectFlags);
-                output.Write(packet.KeepAlivePeriod);
-                output.WriteWithLengthPrefix(packet.ClientId);
-
-                if (packet.WillMessage != null)
-                {
-                    output.WriteWithLengthPrefix(packet.WillMessage.Topic);
-                    output.WriteWithLengthPrefix(packet.WillMessage.Payload);
-                }
-
-                if (packet.Username != null)
-                {
-                    output.WriteWithLengthPrefix(packet.Username);
-                }
-
-                if (packet.Password != null)
-                {
-                    output.WriteWithLengthPrefix(packet.Password);
-                }
-
-                output.InjectFixedHeader(MqttControlPacketType.Connect);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttConnAckPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                var connectAcknowledgeFlags = new ByteWriter();
-                connectAcknowledgeFlags.Write(packet.IsSessionPresent);
-
-                output.Write(connectAcknowledgeFlags);
-                output.Write((byte)packet.ConnectReturnCode);
-
-                output.InjectFixedHeader(MqttControlPacketType.ConnAck);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttDisconnectPacket packet, IMqttCommunicationChannel destination)
-        {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, destination);
-        }
-
-        private static Task SerializeAsync(MqttPingReqPacket packet, IMqttCommunicationChannel destination)
-        {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.PingReq, destination);
-        }
-
-        private static Task SerializeAsync(MqttPingRespPacket packet, IMqttCommunicationChannel destination)
-        {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.PingResp, destination);
-        }
-
-        private static Task SerializeAsync(MqttPublishPacket packet, IMqttCommunicationChannel destination)
-        {
-            ValidatePublishPacket(packet);
-
-            using (var output = new MqttPacketWriter())
-            {
-                output.WriteWithLengthPrefix(packet.Topic);
-
-                if (packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
-                {
-                    output.Write(packet.PacketIdentifier);
-                }
-                else
-                {
-                    if (packet.PacketIdentifier > 0)
-                    {
-                        throw new MqttProtocolViolationException("Packet identifier must be empty if QoS == 0 [MQTT-2.3.1-5].");
-                    }
-                }
-
-                if (packet.Payload?.Length > 0)
-                {
-                    output.Write(packet.Payload);
-                }
-
-                var fixedHeader = new ByteWriter();
-                fixedHeader.Write(packet.Retain);
-                fixedHeader.Write((byte)packet.QualityOfServiceLevel, 2);
-                fixedHeader.Write(packet.Dup);
-
-                output.InjectFixedHeader(MqttControlPacketType.Publish, fixedHeader.Value);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttPubAckPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.PubAck);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttPubRecPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.PubRec);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static async Task SerializeAsync(MqttPubRelPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.PubRel, 0x02);
-                await output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttPubCompPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.PubComp);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttSubscribePacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                if (packet.TopicFilters?.Count > 0)
-                {
-                    foreach (var topicFilter in packet.TopicFilters)
-                    {
-                        output.WriteWithLengthPrefix(topicFilter.Topic);
-                        output.Write((byte)topicFilter.QualityOfServiceLevel);
-                    }
-                }
-
-                output.InjectFixedHeader(MqttControlPacketType.Subscribe, 0x02);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttSubAckPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                if (packet.SubscribeReturnCodes?.Any() == true)
-                {
-                    foreach (var packetSubscribeReturnCode in packet.SubscribeReturnCodes)
-                    {
-                        output.Write((byte)packetSubscribeReturnCode);
-                    }
-                }
-
-                output.InjectFixedHeader(MqttControlPacketType.SubAck);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttUnsubscribePacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                if (packet.TopicFilters?.Any() == true)
-                {
-                    foreach (var topicFilter in packet.TopicFilters)
-                    {
-                        output.WriteWithLengthPrefix(topicFilter);
-                    }
-                }
-
-                output.InjectFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeAsync(MqttUnsubAckPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.UnsubAck);
-                return output.WriteToAsync(destination);
-            }
-        }
-
-        private static Task SerializeEmptyPacketAsync(MqttControlPacketType type, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
-            {
-                output.InjectFixedHeader(type);
-                return output.WriteToAsync(destination);
-            }
-        }
-    }
-}

MQTTnet.Core/Server/ConnectedMqttClient.cs

@@ -0,0 +1,11 @@
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Core.Server
+{
+    public class ConnectedMqttClient
+    {
+        public string ClientId { get; set; }
+
+        public MqttProtocolVersion ProtocolVersion { get; set; }
+    }
+}

MQTTnet.Core/Server/IMqttServer.cs

@@ -9,7 +9,7 @@ namespace MQTTnet.Core.Server
         event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
         event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
 
-        IList<string> GetConnectedClients();
+        IList<ConnectedMqttClient> GetConnectedClients();
         void InjectClient(string identifier, IMqttCommunicationAdapter adapter);
         void Publish(MqttApplicationMessage applicationMessage);
         void Start();

MQTTnet.Core/Server/IMqttServerFactory.cs

@@ -0,0 +1,7 @@
+namespace MQTTnet.Core.Server
+{
+    public interface IMqttServerFactory
+    {
+        IMqttServer CreateMqttServer(MqttServerOptions options);
+    }
+}

MQTTnet.Core/Server/MqttClientMessageQueue.cs

@@ -1,24 +1,21 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
+using System.Collections.Concurrent;
 using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Exceptions;
-using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
+using System.Linq;
 
 namespace MQTTnet.Core.Server
 {
     public sealed class MqttClientMessageQueue
     {
-        private readonly List<MqttClientPublishPacketContext> _pendingPublishPackets = new List<MqttClientPublishPacketContext>();
-        private readonly AsyncGate _gate = new AsyncGate();
+        private readonly BlockingCollection<MqttPublishPacket> _pendingPublishPackets = new BlockingCollection<MqttPublishPacket>();
 
         private readonly MqttServerOptions _options;
         private CancellationTokenSource _cancellationTokenSource;
-        private IMqttCommunicationAdapter _adapter;
 
         public MqttClientMessageQueue(MqttServerOptions options)
         {
@@ -32,102 +29,60 @@ namespace MQTTnet.Core.Server
                 throw new InvalidOperationException($"{nameof(MqttClientMessageQueue)} already started.");
             }
 
-            _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
+            if (adapter == null) throw new ArgumentNullException(nameof(adapter));
             _cancellationTokenSource = new CancellationTokenSource();
 
-            Task.Run(() => SendPendingPublishPacketsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
+            Task.Run(() => SendPendingPublishPacketsAsync(_cancellationTokenSource.Token, adapter), _cancellationTokenSource.Token);
         }
 
         public void Stop()
         {
-            _adapter = null;
             _cancellationTokenSource?.Cancel();
             _cancellationTokenSource = null;
+            _pendingPublishPackets?.Dispose();
         }
 
         public void Enqueue(MqttPublishPacket publishPacket)
         {
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
 
-            lock (_pendingPublishPackets)
-            {
-                _pendingPublishPackets.Add(new MqttClientPublishPacketContext(publishPacket));
-                _gate.Set();
-            }
+            _pendingPublishPackets.Add(publishPacket);
         }
 
-        private async Task SendPendingPublishPacketsAsync(CancellationToken cancellationToken)
+        private async Task SendPendingPublishPacketsAsync(CancellationToken cancellationToken, IMqttCommunicationAdapter adapter)
         {
+            var consumable = _pendingPublishPackets.GetConsumingEnumerable();
             while (!cancellationToken.IsCancellationRequested)
             {
+                if (_pendingPublishPackets.Count == 0)
+                {
+                    await Task.Delay(TimeSpan.FromMilliseconds(5), cancellationToken).ConfigureAwait(false);
+                    continue;
+                }
+
+                var packets = consumable.Take(_pendingPublishPackets.Count).ToList();
                 try
                 {
-                    await _gate.WaitOneAsync();
-                    if (cancellationToken.IsCancellationRequested)
+                    await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, packets).ConfigureAwait(false);
+                }
+                catch (MqttCommunicationException exception)
+                {
+                    MqttTrace.Warning(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
+                    foreach (var publishPacket in packets)
                     {
-                        return;
-                    }
-
-                    if (_adapter == null)
-                    {
-                        continue;
-                    }
-
-                    List<MqttClientPublishPacketContext> pendingPublishPackets;
-                    lock (_pendingPublishPackets)
-                    {
-                        pendingPublishPackets = _pendingPublishPackets.ToList();
-                    }
-
-                    foreach (var publishPacket in pendingPublishPackets)
-                    {
-                        await TrySendPendingPublishPacketAsync(publishPacket);
+                        publishPacket.Dup = true;
+                        _pendingPublishPackets.Add(publishPacket, cancellationToken);
                     }
                 }
-                catch (Exception e)
+                catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttClientMessageQueue), e, "Error while sending pending publish packets.");
+                    MqttTrace.Error(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
+                    foreach (var publishPacket in packets)
+                    {
+                        publishPacket.Dup = true;
+                        _pendingPublishPackets.Add(publishPacket, cancellationToken);
+                    }
                 }
-                finally
-                {
-                    Cleanup();
-                }               
-            }
-        }
-
-        private async Task TrySendPendingPublishPacketAsync(MqttClientPublishPacketContext publishPacketContext)
-        {
-            try
-            {
-                if (_adapter == null)
-                {
-                    return;
-                }
-
-                publishPacketContext.PublishPacket.Dup = publishPacketContext.SendTries > 0;
-                await _adapter.SendPacketAsync(publishPacketContext.PublishPacket, _options.DefaultCommunicationTimeout);
-
-                publishPacketContext.IsSent = true;
-            }
-            catch (MqttCommunicationException exception)
-            {
-                MqttTrace.Warning(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
-            }
-            catch (Exception exception)
-            {
-                MqttTrace.Error(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
-            }
-            finally
-            {
-                publishPacketContext.SendTries++;
-            }
-        }
-
-        private void Cleanup()
-        {
-            lock (_pendingPublishPackets)
-            {
-                _pendingPublishPackets.RemoveAll(p => p.IsSent);
             }
         }
     }

MQTTnet.Core/Server/MqttClientPublishPacketContext.cs

@@ -1,19 +0,0 @@
-using System;
-using MQTTnet.Core.Packets;
-
-namespace MQTTnet.Core.Server
-{
-    public sealed class MqttClientPublishPacketContext
-    {
-        public MqttClientPublishPacketContext(MqttPublishPacket publishPacket)
-        {
-            PublishPacket = publishPacket ?? throw new ArgumentNullException(nameof(publishPacket));
-        }
-
-        public MqttPublishPacket PublishPacket { get; }
-
-        public int SendTries { get; set; }
-
-        public bool IsSent { get; set; }
-    }
-}

MQTTnet.Core/Server/MqttClientSession.cs

@@ -21,7 +21,6 @@ namespace MQTTnet.Core.Server
         private readonly MqttServerOptions _options;
 
         private CancellationTokenSource _cancellationTokenSource;
-        private IMqttCommunicationAdapter _adapter;
         private string _identifier;
         private MqttApplicationMessage _willApplicationMessage;
 
@@ -36,7 +35,9 @@ namespace MQTTnet.Core.Server
 
         public string ClientId { get; }
 
-        public bool IsConnected => _adapter != null;
+        public bool IsConnected => Adapter != null;
+
+        public IMqttCommunicationAdapter Adapter { get; private set; }
 
         public async Task RunAsync(string identifier, MqttApplicationMessage willApplicationMessage, IMqttCommunicationAdapter adapter)
         {
@@ -47,14 +48,14 @@ namespace MQTTnet.Core.Server
             try
             {
                 _identifier = identifier;
-                _adapter = adapter;
+                Adapter = adapter;
                 _cancellationTokenSource = new CancellationTokenSource();
 
                 _messageQueue.Start(adapter);
                 while (!_cancellationTokenSource.IsCancellationRequested)
                 {
-                    var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero);
-                    await HandleIncomingPacketAsync(packet);
+                    var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero, _cancellationTokenSource.Token).ConfigureAwait(false);
+                    await HandleIncomingPacketAsync(packet).ConfigureAwait(false);
                 }
             }
             catch (MqttCommunicationException)
@@ -62,7 +63,7 @@ namespace MQTTnet.Core.Server
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClientSession), exception, $"Client '{_identifier}': Unhandled exception while processing client packets.");
+                MqttTrace.Error(nameof(MqttClientSession), exception, "Client '{0}': Unhandled exception while processing client packets.", _identifier);
             }
             finally
             {
@@ -73,9 +74,9 @@ namespace MQTTnet.Core.Server
 
                 _messageQueue.Stop();
                 _cancellationTokenSource.Cancel();
-                _adapter = null;
+                Adapter = null;
 
-                MqttTrace.Information(nameof(MqttClientSession), $"Client '{_identifier}': Disconnected.");
+                MqttTrace.Information(nameof(MqttClientSession), "Client '{0}': Disconnected.", _identifier);
             }
         }
 
@@ -89,7 +90,7 @@ namespace MQTTnet.Core.Server
             }
 
             _messageQueue.Enqueue(publishPacket);
-            MqttTrace.Verbose(nameof(MqttClientSession), $"Client '{_identifier}: Enqueued pending publish packet.");
+            MqttTrace.Verbose(nameof(MqttClientSession), "Client '{0}': Enqueued pending publish packet.", _identifier);
         }
 
         public void Dispose()
@@ -102,12 +103,12 @@ namespace MQTTnet.Core.Server
         {
             if (packet is MqttSubscribePacket subscribePacket)
             {
-                return _adapter.SendPacketAsync(_subscriptionsManager.Subscribe(subscribePacket), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Subscribe(subscribePacket));
             }
 
             if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                return _adapter.SendPacketAsync(_subscriptionsManager.Unsubscribe(unsubscribePacket), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Unsubscribe(unsubscribePacket));
             }
 
             if (packet is MqttPublishPacket publishPacket)
@@ -122,7 +123,7 @@ namespace MQTTnet.Core.Server
 
             if (packet is MqttPubRecPacket pubRecPacket)
             {
-                return _adapter.SendPacketAsync(pubRecPacket.CreateResponse<MqttPubRelPacket>(), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, pubRecPacket.CreateResponse<MqttPubRelPacket>());
             }
 
             if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
@@ -133,7 +134,7 @@ namespace MQTTnet.Core.Server
 
             if (packet is MqttPingReqPacket)
             {
-                return _adapter.SendPacketAsync(new MqttPingRespPacket(), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPingRespPacket());
             }
 
             if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
@@ -142,7 +143,7 @@ namespace MQTTnet.Core.Server
                 return Task.FromResult((object)null);
             }
 
-            MqttTrace.Warning(nameof(MqttClientSession), $"Client '{_identifier}': Received not supported packet ({packet}). Closing connection.");
+            MqttTrace.Warning(nameof(MqttClientSession), "Client '{0}': Received not supported packet ({1}). Closing connection.", _identifier, packet);
             _cancellationTokenSource.Cancel();
 
             return Task.FromResult((object)null);
@@ -159,7 +160,7 @@ namespace MQTTnet.Core.Server
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 _publishPacketReceivedCallback(this, publishPacket);
-                return _adapter.SendPacketAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
@@ -172,7 +173,7 @@ namespace MQTTnet.Core.Server
 
                 _publishPacketReceivedCallback(this, publishPacket);
 
-                return _adapter.SendPacketAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
             }
 
             throw new MqttCommunicationException("Received a not supported QoS level.");
@@ -185,7 +186,7 @@ namespace MQTTnet.Core.Server
                 _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
 
-            return _adapter.SendPacketAsync(new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+            return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier });
         }
     }
 }

MQTTnet.Core/Server/MqttClientSessionsManager.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Diagnostics;
@@ -28,32 +29,34 @@ namespace MQTTnet.Core.Server
         {
             try
             {
-                var connectPacket = await eventArgs.ClientAdapter.ReceivePacketAsync(_options.DefaultCommunicationTimeout) as MqttConnectPacket;
-                if (connectPacket == null)
+                if (!(await eventArgs.ClientAdapter.ReceivePacketAsync(_options.DefaultCommunicationTimeout, CancellationToken.None).ConfigureAwait(false) is MqttConnectPacket connectPacket))
                 {
                     throw new MqttProtocolViolationException("The first packet from a client must be a 'CONNECT' packet [MQTT-3.1.0-1].");
                 }
 
+                // Switch to the required protocol version before sending any response.
+                eventArgs.ClientAdapter.PacketSerializer.ProtocolVersion = connectPacket.ProtocolVersion;
+
                 var connectReturnCode = ValidateConnection(connectPacket);
                 if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
                 {
-                    await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                    await eventArgs.ClientAdapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, CancellationToken.None, new MqttConnAckPacket
                     {
                         ConnectReturnCode = connectReturnCode
-                    }, _options.DefaultCommunicationTimeout);
+                    }).ConfigureAwait(false);
 
                     return;
                 }
 
                 var clientSession = GetOrCreateClientSession(connectPacket);
 
-                await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                await eventArgs.ClientAdapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, CancellationToken.None, new MqttConnAckPacket
                 {
                     ConnectReturnCode = connectReturnCode,
                     IsSessionPresent = clientSession.IsExistingSession
-                }, _options.DefaultCommunicationTimeout);
+                }).ConfigureAwait(false);
 
-                await clientSession.Session.RunAsync(eventArgs.Identifier, connectPacket.WillMessage, eventArgs.ClientAdapter);
+                await clientSession.Session.RunAsync(eventArgs.Identifier, connectPacket.WillMessage, eventArgs.ClientAdapter).ConfigureAwait(false);
             }
             catch (Exception exception)
             {
@@ -61,7 +64,7 @@ namespace MQTTnet.Core.Server
             }
             finally
             {
-                await eventArgs.ClientAdapter.DisconnectAsync();
+                await eventArgs.ClientAdapter.DisconnectAsync(_options.DefaultCommunicationTimeout).ConfigureAwait(false);
             }
         }
 
@@ -73,11 +76,15 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public IList<string> GetConnectedClients()
+        public IList<ConnectedMqttClient> GetConnectedClients()
         {
             lock (_syncRoot)
             {
-                return _clientSessions.Where(s => s.Value.IsConnected).Select(s => s.Key).ToList();
+                return _clientSessions.Where(s => s.Value.IsConnected).Select(s => new ConnectedMqttClient
+                {
+                    ClientId = s.Value.ClientId,
+                    ProtocolVersion = s.Value.Adapter.PacketSerializer.ProtocolVersion
+                }).ToList();
             }
         }
 
@@ -104,11 +111,11 @@ namespace MQTTnet.Core.Server
                         _clientSessions.Remove(connectPacket.ClientId);
                         clientSession.Dispose();
                         clientSession = null;
-                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Disposed existing session of client '{connectPacket.ClientId}'.");
+                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), "Disposed existing session of client '{0}'.", connectPacket.ClientId);
                     }
                     else
                     {
-                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Reusing existing session of client '{connectPacket.ClientId}'.");
+                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), "Reusing existing session of client '{0}'.", connectPacket.ClientId);
                     }
                 }
 
@@ -120,7 +127,7 @@ namespace MQTTnet.Core.Server
                     clientSession = new MqttClientSession(connectPacket.ClientId, _options, DispatchPublishPacket);
                     _clientSessions[connectPacket.ClientId] = clientSession;
 
-                    MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Created a new session for client '{connectPacket.ClientId}'.");
+                    MqttTrace.Verbose(nameof(MqttClientSessionsManager), "Created a new session for client '{0}'.", connectPacket.ClientId);
                 }
 
                 return new GetOrCreateClientSessionResult { IsExistingSession = isExistingSession, Session = clientSession };

MQTTnet.Core/Server/MqttServer.cs

@@ -20,12 +20,12 @@ namespace MQTTnet.Core.Server
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
             _adapters = adapters ?? throw new ArgumentNullException(nameof(adapters));
-            
+
             _clientSessionsManager = new MqttClientSessionsManager(options);
             _clientSessionsManager.ApplicationMessageReceived += (s, e) => ApplicationMessageReceived?.Invoke(s, e);
         }
 
-        public IList<string> GetConnectedClients()
+        public IList<ConnectedMqttClient> GetConnectedClients()
         {
             return _clientSessionsManager.GetConnectedClients();
         }
@@ -61,7 +61,7 @@ namespace MQTTnet.Core.Server
                 adapter.ClientConnected += OnClientConnected;
                 adapter.Start(_options);
             }
-            
+
             MqttTrace.Information(nameof(MqttServer), "Started.");
         }
 
@@ -84,7 +84,7 @@ namespace MQTTnet.Core.Server
 
         private void OnClientConnected(object sender, MqttClientConnectedEventArgs eventArgs)
         {
-            MqttTrace.Information(nameof(MqttServer), $"Client '{eventArgs.Identifier}': Connected.");
+            MqttTrace.Information(nameof(MqttServer), "Client '{0}': Connected.", eventArgs.Identifier);
             ClientConnected?.Invoke(this, eventArgs);
 
             Task.Run(() => _clientSessionsManager.RunClientSessionAsync(eventArgs), _cancellationTokenSource.Token);

MQTTnet.Core/Server/MqttServerOptions.cs

@@ -9,7 +9,7 @@ namespace MQTTnet.Core.Server
         public MqttServerDefaultEndpointOptions DefaultEndpointOptions { get; } = new MqttServerDefaultEndpointOptions();
 
         public MqttServerTlsEndpointOptions TlsEndpointOptions { get; } = new MqttServerTlsEndpointOptions();
-        
+
         public int ConnectionBacklog { get; set; } = 10;
 
         public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(15);

MQTTnet.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26430.15
+VisualStudioVersion = 15.0.26730.16
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.Core.Tests", "Tests\MQTTnet.Core.Tests\MQTTnet.Core.Tests.csproj", "{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}"
 EndProject
@@ -27,6 +27,13 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Build", "Build", "{67C28AC1
 		Build\MQTTnet.nuspec = Build\MQTTnet.nuspec
 	EndProjectSection
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{B3F60ECB-45BA-4C66-8903-8BB89CA67998}"
+	ProjectSection(SolutionItems) = preProject
+		README.md = README.md
+	EndProjectSection
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.TestApp.NetCore", "Tests\MQTTnet.TestApp.NetCore\MQTTnet.TestApp.NetCore.csproj", "{3D283AAD-AAA8-4339-8394-52F80B6304DB}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -91,18 +98,18 @@ Global
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|ARM.ActiveCfg = Debug|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|ARM.Build.0 = Debug|Any CPU
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.ActiveCfg = Debug|x64
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.Build.0 = Debug|x64
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.ActiveCfg = Debug|x86
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.Build.0 = Debug|x86
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x64.Build.0 = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Debug|x86.Build.0 = Debug|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|Any CPU.Build.0 = Release|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|ARM.ActiveCfg = Release|Any CPU
 		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|ARM.Build.0 = Release|Any CPU
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.ActiveCfg = Release|x64
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.Build.0 = Release|x64
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.ActiveCfg = Release|x86
-		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.Build.0 = Release|x86
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.ActiveCfg = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x64.Build.0 = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.ActiveCfg = Release|Any CPU
+		{2ECB99E4-72D0-4C23-99BA-93D511D3967D}.Release|x86.Build.0 = Release|Any CPU
 		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D9D74F33-6943-49B2-B765-7BD589082098}.Debug|ARM.ActiveCfg = Debug|Any CPU
@@ -145,10 +152,10 @@ Global
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|ARM.ActiveCfg = Debug|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|ARM.Build.0 = Debug|Any CPU
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x64.ActiveCfg = Debug|x64
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x64.Build.0 = Debug|x64
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.ActiveCfg = Debug|x86
-		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.Build.0 = Debug|x86
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x64.Build.0 = Debug|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Debug|x86.Build.0 = Debug|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|Any CPU.Build.0 = Release|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|ARM.ActiveCfg = Release|Any CPU
@@ -157,6 +164,22 @@ Global
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x64.Build.0 = Release|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x86.ActiveCfg = Release|Any CPU
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2}.Release|x86.Build.0 = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|ARM.ActiveCfg = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|ARM.Build.0 = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|x64.Build.0 = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Debug|x86.Build.0 = Debug|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|ARM.ActiveCfg = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|ARM.Build.0 = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|x64.ActiveCfg = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|x64.Build.0 = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|x86.ActiveCfg = Release|Any CPU
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -168,5 +191,9 @@ Global
 		{D9D74F33-6943-49B2-B765-7BD589082098} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
 		{FF1F72D6-9524-4422-9497-3CC0002216ED} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
 		{3587E506-55A2-4EB3-99C7-DC01E42D25D2} = {32A630A7-2598-41D7-B625-204CD906F5FB}
+		{3D283AAD-AAA8-4339-8394-52F80B6304DB} = {9248C2E1-B9D6-40BF-81EC-86004D7765B4}
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {07536672-5CBC-4BE3-ACE0-708A431A7894}
 	EndGlobalSection
 EndGlobal

MQTTnet.sln.DotSettings

@@ -0,0 +1,7 @@
+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/CodeStyle/CodeFormatting/CSharpFormat/SPACE_WITHIN_METHOD_CALL_PARENTHESES/@EntryValue">False</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeStyle/CodeFormatting/CSharpFormat/SPACE_WITHIN_METHOD_PARENTHESES/@EntryValue">False</s:Boolean>
+	<s:Boolean x:Key="/Default/CodeStyle/CodeFormatting/CSharpFormat/SPACE_WITHIN_PARENTHESES/@EntryValue">False</s:Boolean>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EAddAccessorOwnerDeclarationBracesMigration/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateBlankLinesAroundFieldToBlankLinesAroundProperty/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateThisQualifierSettings/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

README.md

@@ -3,42 +3,54 @@
 </p>
 
 [![NuGet Badge](https://buildstats.info/nuget/MQTTnet)](https://www.nuget.org/packages/MQTTnet)
+[![BCH compliance](https://bettercodehub.com/edge/badge/chkr1011/MQTTnet?branch=master)](https://bettercodehub.com/)
 
 # MQTTnet
-MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server. The implementation is based on the documentation from http://mqtt.org/.
+MQTTnet is a .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker). The implementation is based on the documentation from http://mqtt.org/.
 
-## Features
-* MQTT client included
-* MQTT server (broker) included
-* TLS 1.2 support for client and server (but not UWP servers)
+# Features
+
+### General
 * Async support
-* Rx support (via another project)
-* List of connected clients available (server only)
-* Extensible communication channels (i.e. In-Memory, TCP, TCP+SSL, WebSockets (not included in this project))
-* Server is able to publish its own messages (no loopback client required)
-* Access to internal trace messages
-* Extensible client credential validation (server only)
-* Unit tested (50+ tests)
+* TLS 1.2 support for client and server (but not UWP servers)
+* Extensible communication channels (i.e. In-Memory, TCP, TCP+TLS, WS)
 * Lightweight (only the low level implementation of MQTT, no overhead)
+* Performance optimized (processing ~27.000 messages / second)*
 * Interfaces included for mocking and testing
+* Access to internal trace messages
+* Unit tested (57+ tests)
 
-## Supported frameworks
+\* Tested on local machine with MQTTnet client and server running in the same process using the TCP channel. The app for verification is part of this repository and stored in _/Tests/MQTTnet.TestApp.NetFramework_.
+
+### Client
+* Rx support (via another project)
+* Communication via TCP (+TLS) or WS (WebSocket)
+
+### Server (broker)
+* List of connected clients available
+* Supports connected clients with different protocol versions at the same time
+* Able to publish its own messages (no loopback client required)
+* Able to receive every messages (no loopback client required)
+* Extensible client credential validation
+
+# Supported frameworks
 * .NET Standard 1.3+
 * .NET Core 1.1+
 * .NET Core App 1.1+
 * .NET Framework 4.5.2+ (x86, x64, AnyCPU)
 * Universal Windows (UWP) 10.0.10240+ (x86, x64, ARM, AnyCPU)
 
-## Supported MQTT versions
+# Supported MQTT versions
 * 3.1.1
+* 3.1.0
 
-## Nuget
+# Nuget
 This library is available as a nuget package: https://www.nuget.org/packages/MQTTnet/
 
-## Contributions
+# Contributions
 If you want to contribute to this project just create a pull request.
 
-## References
+# References
 This library is used in the following projects:
 
 * MQTT Client Rx (Wrapper for Reactive Extensions, https://github.com/1iveowl/MQTTClient.rx)
@@ -46,8 +58,8 @@ This library is used in the following projects:
 
 If you use this library and want to see your project here please let me know.
 
-# MqttClient
-## Example
+# Examples
+## MqttClient
 
 ```csharp
 var options = new MqttClientOptions
@@ -68,14 +80,12 @@ client.ApplicationMessageReceived += (s, e) =>
 
 client.Connected += async (s, e) =>
 {
-    Console.WriteLine("### CONNECTED WITH SERVER ###");
+    Console.WriteLine("### CONNECTED WITH SERVER, SUBSCRIBING ###");
 
     await client.SubscribeAsync(new List<TopicFilter>
     {
         new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)
     });
-
-    Console.WriteLine("### SUBSCRIBED ###");
 };
 
 client.Disconnected += async (s, e) => 
@@ -104,24 +114,17 @@ catch
 
 Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
 
+var messageFactory = new MqttApplicationMessageFactory();
 while (true)
 {
     Console.ReadLine();
 
-    var applicationMessage = new MqttApplicationMessage(
-        "A/B/C",
-        Encoding.UTF8.GetBytes("Hello World"),
-        MqttQualityOfServiceLevel.AtLeastOnce,
-        false
-    );
-
+    var applicationMessage = messageFactory.CreateApplicationMessage("myTopic", "Hello World", MqttQualityOfServiceLevel.AtLeastOnce);
     await client.PublishAsync(applicationMessage);
 }
 ```
 
-# MqttServer
-
-## Example 
+## MqttServer
 
 ```csharp
 var options = new MqttServerOptions
@@ -147,4 +150,4 @@ Console.WriteLine("Press any key to exit.");
 Console.ReadLine();
 
 mqttServer.Stop();
-```
+```

Tests/MQTTnet.Core.Tests/ExtensionTests.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Core.Exceptions;
+using MQTTnet.Core.Internal;
+
+namespace MQTTnet.Core.Tests
+{
+    [TestClass]
+    public class ExtensionTests
+    {
+        [ExpectedException(typeof(MqttCommunicationTimedOutException))]
+        [TestMethod]
+        public async Task TimeoutAfter()
+        {
+            await Task.Delay(TimeSpan.FromMilliseconds(500)).TimeoutAfter(TimeSpan.FromMilliseconds(100));
+        }
+
+        [ExpectedException(typeof(MqttCommunicationTimedOutException))]
+        [TestMethod]
+        public async Task TimeoutAfterWithResult()
+        {
+            await Task.Delay(TimeSpan.FromMilliseconds(500)).ContinueWith(t => 5).TimeoutAfter(TimeSpan.FromMilliseconds(100));
+        }
+
+        [TestMethod]
+        public async Task TimeoutAfterCompleteInTime()
+        {
+            var result = await Task.Delay(TimeSpan.FromMilliseconds(100)).ContinueWith(t => 5).TimeoutAfter(TimeSpan.FromMilliseconds(500));
+            Assert.AreEqual(5, result);
+        }
+
+        [TestMethod]
+        public async Task TimeoutAfterWithInnerException()
+        {
+            try
+            {
+                await Task.Run(() =>
+                {
+                    var iis = new int[0];
+                    iis[1] = 0;
+                }).TimeoutAfter(TimeSpan.FromSeconds(1));
+
+                Assert.Fail();
+            }
+            catch (MqttCommunicationException e)
+            {
+                Assert.IsTrue(e.InnerException is IndexOutOfRangeException);
+            }
+        }
+
+        [TestMethod]
+        public async Task TimeoutAfterWithInnerExceptionWithResult()
+        {
+            try
+            {
+                var r = await Task.Run(() =>
+                {
+                    var iis = new int[0];
+                    return iis[1];
+                }).TimeoutAfter(TimeSpan.FromSeconds(1));
+
+                Assert.Fail();
+            }
+            catch (MqttCommunicationException e)
+            {
+                Assert.IsTrue(e.InnerException is IndexOutOfRangeException);
+            }
+        }
+
+        [TestMethod]
+        public async Task TimeoutAfterMemoryUsage()
+        {
+            var tasks = Enumerable.Range(0, 100000)
+                .Select(i => Task.Delay(TimeSpan.FromMilliseconds(1)).TimeoutAfter(TimeSpan.FromMinutes(1)));
+
+            await Task.WhenAll(tasks);
+            AssertIsLess(3_000_000, GC.GetTotalMemory(true));
+        }
+
+        private static void AssertIsLess(long bound, long actual)
+        {
+            if (bound < actual)
+            {
+                Assert.Fail($"value must be less than {bound:N0} but is {actual:N0}");
+            }
+        }
+    }
+}

Tests/MQTTnet.Core.Tests/MQTTnet.Core.Tests.csproj

@@ -86,7 +86,8 @@
   <ItemGroup>
     <Compile Include="ByteReaderTests.cs" />
     <Compile Include="ByteWriterTests.cs" />
-    <Compile Include="DefaultMqttV311PacketSerializerTests.cs" />
+    <Compile Include="ExtensionTests.cs" />
+    <Compile Include="MqttPacketSerializerTests.cs" />
     <Compile Include="MqttServerTests.cs" />
     <Compile Include="MqttSubscriptionsManagerTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />

Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs

@@ -1,8 +1,10 @@
 using System;
 using System.IO;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Packets;
@@ -12,8 +14,23 @@ using MQTTnet.Core.Serializer;
 namespace MQTTnet.Core.Tests
 {
     [TestClass]
-    public class DefaultMqttV311PacketSerializerTests
+    public class MqttPacketSerializerTests
     {
+        [TestMethod]
+        public void SerializeV310_MqttConnectPacket()
+        {
+            var p = new MqttConnectPacket
+            {
+                ClientId = "XYZ",
+                Password = "PASS",
+                Username = "USER",
+                KeepAlivePeriod = 123,
+                CleanSession = true
+            };
+
+            SerializeAndCompare(p, "EB0ABE1RSXNkcAPCAHsAA1hZWgAEVVNFUgAEUEFTUw==", MqttProtocolVersion.V310);
+        }
+
         [TestMethod]
         public void SerializeV311_MqttConnectPacket()
         {
@@ -96,6 +113,17 @@ namespace MQTTnet.Core.Tests
             SerializeAndCompare(p, "IAIBBQ==");
         }
 
+        [TestMethod]
+        public void SerializeV310_MqttConnAckPacket()
+        {
+            var p = new MqttConnAckPacket
+            {
+                ConnectReturnCode = MqttConnectReturnCode.ConnectionAccepted
+            };
+
+            SerializeAndCompare(p, "IAIAAA==", MqttProtocolVersion.V310);
+        }
+
         [TestMethod]
         public void DeserializeV311_MqttConnAckPacket()
         {
@@ -365,6 +393,12 @@ namespace MQTTnet.Core.Tests
         {
             private readonly MemoryStream _stream = new MemoryStream();
 
+            public Stream ReceiveStream => _stream;
+
+            public Stream RawReceiveStream => _stream;
+
+            public Stream SendStream => _stream;
+
             public bool IsConnected { get; } = true;
 
             public TestChannel()
@@ -377,24 +411,14 @@ namespace MQTTnet.Core.Tests
                 _stream.Position = 0;
             }
 
-            public async Task ConnectAsync(MqttClientOptions options)
+            public Task ConnectAsync(MqttClientOptions options)
             {
-                await Task.FromResult(0);
+                return Task.FromResult(0);
             }
 
-            public async Task DisconnectAsync()
+            public Task DisconnectAsync()
             {
-                await Task.FromResult(0);
-            }
-
-            public async Task WriteAsync(byte[] buffer)
-            {
-                await _stream.WriteAsync(buffer, 0, buffer.Length);
-            }
-
-            public async Task ReadAsync(byte[] buffer)
-            {
-                await _stream.ReadAsync(buffer, 0, buffer.Length);
+                return Task.FromResult(0);
             }
 
             public byte[] ToArray()
@@ -403,32 +427,32 @@ namespace MQTTnet.Core.Tests
             }
         }
 
-        private void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value)
+        private static void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
-            var serializer = new MqttV311PacketSerializer();
-            var channel = new TestChannel();
-            serializer.SerializeAsync(packet, channel).Wait();
-            var buffer = channel.ToArray();
+            var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
+            var buffer = serializer.Serialize(packet);
 
             Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(buffer));
         }
 
-        private void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value)
+        private static void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value)
         {
-            var serializer = new MqttV311PacketSerializer();
+            var serializer = new MqttPacketSerializer();
 
-            var channel1 = new TestChannel();
-            serializer.SerializeAsync(packet, channel1).Wait();
-            var buffer1 = channel1.ToArray();
+            var buffer1 = serializer.Serialize(packet);
 
-            var channel2 = new TestChannel(buffer1);
-            var deserializedPacket = serializer.DeserializeAsync(channel2).Result;
-            var buffer2 = channel2.ToArray();
+            using (var headerStream = new MemoryStream(buffer1))
+            {
+                var header = MqttPacketReader.ReadHeaderFromSource(headerStream, CancellationToken.None);
 
-            var channel3 = new TestChannel(buffer2);
-            serializer.SerializeAsync(deserializedPacket, channel3).Wait();
+                using (var bodyStream = new MemoryStream(buffer1, (int)headerStream.Position, header.BodyLength))
+                {
+                    var deserializedPacket = serializer.Deserialize(new ReceivedMqttPacket(header, bodyStream));
+                    var buffer2 = serializer.Serialize(deserializedPacket);
 
-            Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(channel3.ToArray()));
+                    Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(buffer2));
+                }
+            }
         }
     }
 }

Tests/MQTTnet.Core.Tests/MqttServerTests.cs

@@ -13,36 +13,36 @@ namespace MQTTnet.Core.Tests
     public class MqttServerTests
     {
         [TestMethod]
-        public async Task MqttServer_PublishSimple_AtMostOnce()
+        public void MqttServer_PublishSimple_AtMostOnce()
         {
-            await TestPublishAsync(
+            TestPublishAsync(
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtMostOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtMostOnce,
-                1);
+                1).Wait();
         }
 
         [TestMethod]
-        public async Task MqttServer_PublishSimple_AtLeastOnce()
+        public void MqttServer_PublishSimple_AtLeastOnce()
         {
-            await TestPublishAsync(
+            TestPublishAsync(
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtLeastOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.AtLeastOnce,
-                1);
+                1).Wait();
         }
 
         [TestMethod]
-        public async Task MqttServer_PublishSimple_ExactlyOnce()
+        public void MqttServer_PublishSimple_ExactlyOnce()
         {
-            await TestPublishAsync(
+            TestPublishAsync(
                 "A/B/C",
                 MqttQualityOfServiceLevel.ExactlyOnce,
                 "A/B/C",
                 MqttQualityOfServiceLevel.ExactlyOnce,
-                1);
+                1).Wait();
         }
 
         [TestMethod]
@@ -91,7 +91,7 @@ namespace MQTTnet.Core.Tests
             await Task.Delay(500);
             Assert.AreEqual(1, receivedMessagesCount);
 
-            await c1.Unsubscribe("a");
+            await c1.UnsubscribeAsync("a");
             await c2.PublishAsync(message);
 
             await Task.Delay(500);
@@ -158,7 +158,7 @@ namespace MQTTnet.Core.Tests
             await c2.PublishAsync(new MqttApplicationMessage(topic, new byte[0], qualityOfServiceLevel, false));
 
             await Task.Delay(500);
-            await c1.Unsubscribe(topicFilter);
+            await c1.UnsubscribeAsync(topicFilter);
 
             await Task.Delay(500);
 

Tests/MQTTnet.Core.Tests/TestMqttCommunicationAdapter.cs

@@ -1,9 +1,12 @@
 using System;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Packets;
+using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Tests
 {
@@ -13,29 +16,35 @@ namespace MQTTnet.Core.Tests
 
         public TestMqttCommunicationAdapter Partner { get; set; }
 
-        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
+        public IMqttPacketSerializer PacketSerializer { get; } = new MqttPacketSerializer();
+
+        public Task ConnectAsync(TimeSpan timeout, MqttClientOptions options)
         {
-            await Task.FromResult(0);
+            return Task.FromResult(0);
         }
 
-        public async Task DisconnectAsync()
+        public Task DisconnectAsync(TimeSpan timeout)
         {
-            await Task.FromResult(0);
+            return Task.FromResult(0);
         }
 
-        public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
+        public Task SendPacketsAsync(TimeSpan timeout, CancellationToken cancellationToken, IEnumerable<MqttBasePacket> packets)
         {
             ThrowIfPartnerIsNull();
 
-            Partner.SendPacketInternal(packet);
-            await Task.FromResult(0);
+            foreach (var packet in packets)
+            {
+                Partner.SendPacketInternal(packet);
+            }
+
+            return Task.FromResult(0);
         }
 
-        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
+        public Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout, CancellationToken cancellationToken)
         {
             ThrowIfPartnerIsNull();
 
-            return await Task.Run(() => _incomingPackets.Take());
+            return Task.Run(() => _incomingPackets.Take(), cancellationToken);
         }
 
         private void SendPacketInternal(MqttBasePacket packet)

Tests/MQTTnet.TestApp.NetCore/MQTTnet.TestApp.NetCore.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <DebugType>Full</DebugType>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\Frameworks\MQTTnet.Netstandard\MQTTnet.NetStandard.csproj" />
+    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj" />
+  </ItemGroup>
+
+</Project>

Tests/MQTTnet.TestApp.NetCore/Program.cs

@@ -0,0 +1,171 @@
+using MQTTnet.Core;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Packets;
+using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Server;
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.TestApp.NetCore
+{
+    public static class Program
+    {
+        public static void Main(string[] args)
+        {
+            Console.WriteLine("MQTTnet - TestApp.NetFramework");
+            Console.WriteLine("1 = Start client");
+            Console.WriteLine("2 = Start server");
+            var pressedKey = Console.ReadKey(true);
+            if (pressedKey.Key == ConsoleKey.D1)
+            {
+                Task.Run(() => RunClientAsync(args));
+                Thread.Sleep(Timeout.Infinite);
+            }
+            else if (pressedKey.Key == ConsoleKey.D2)
+            {
+                Task.Run(() => RunServerAsync(args));
+                Thread.Sleep(Timeout.Infinite);
+            }
+        }
+
+        private static async Task RunClientAsync(string[] arguments)
+        {
+
+            MqttTrace.TraceMessagePublished += (s, e) =>
+            {
+                Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
+                if (e.Exception != null)
+                {
+                    Console.WriteLine(e.Exception);
+                }
+            };
+
+            try
+            {
+                var options = new MqttClientOptions
+                {
+                    Server = "localhost",
+                    ClientId = "XYZ",
+                    CleanSession = true,
+                    ConnectionType = MqttConnectionType.Ws 
+                };
+
+                var client = new MqttClientFactory().CreateMqttClient(options);
+                client.ApplicationMessageReceived += (s, e) =>
+                {
+                    Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
+                    Console.WriteLine($"+ Topic = {e.ApplicationMessage.Topic}");
+                    Console.WriteLine($"+ Payload = {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}");
+                    Console.WriteLine($"+ QoS = {e.ApplicationMessage.QualityOfServiceLevel}");
+                    Console.WriteLine($"+ Retain = {e.ApplicationMessage.Retain}");
+                    Console.WriteLine();
+                };
+
+                client.Connected += async (s, e) =>
+                {
+                    Console.WriteLine("### CONNECTED WITH SERVER ###");
+
+                    await client.SubscribeAsync(new List<TopicFilter>
+                    {
+                        new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)
+                    });
+
+                    Console.WriteLine("### SUBSCRIBED ###");
+                };
+
+                client.Disconnected += async (s, e) =>
+                {
+                    Console.WriteLine("### DISCONNECTED FROM SERVER ###");
+                    await Task.Delay(TimeSpan.FromSeconds(5));
+
+                    try
+                    {
+                        await client.ConnectAsync();
+                    }
+                    catch
+                    {
+                        Console.WriteLine("### RECONNECTING FAILED ###");
+                    }
+                };
+
+                try
+                {
+                    await client.ConnectAsync();
+                }
+                catch (Exception exception)
+                {
+                    Console.WriteLine("### CONNECTING FAILED ###" + Environment.NewLine + exception);
+                }
+
+                Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
+
+                while (true)
+                {
+                    Console.ReadLine();
+
+                    var applicationMessage = new MqttApplicationMessage(
+                        "A/B/C",
+                        Encoding.UTF8.GetBytes("Hello World"),
+                        MqttQualityOfServiceLevel.AtLeastOnce,
+                        false
+                    );
+
+                    await client.PublishAsync(applicationMessage);
+                }
+            }
+            catch (Exception exception)
+            {
+                Console.WriteLine(exception);
+            }
+        }
+
+        private static void RunServerAsync(string[] arguments)
+        {
+            MqttTrace.TraceMessagePublished += (s, e) =>
+            {
+                Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
+                if (e.Exception != null)
+                {
+                    Console.WriteLine(e.Exception);
+                }
+            };
+
+            try
+            {
+                var options = new MqttServerOptions
+                {
+                    ConnectionValidator = p =>
+                    {
+                        if (p.ClientId == "SpecialClient")
+                        {
+                            if (p.Username != "USER" || p.Password != "PASS")
+                            {
+                                return MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
+                            }
+                        }
+
+                        return MqttConnectReturnCode.ConnectionAccepted;
+                    }
+                };
+
+                var mqttServer = new MqttServerFactory().CreateMqttServer(options);
+                mqttServer.Start();
+
+                Console.WriteLine("Press any key to exit.");
+                Console.ReadLine();
+
+                mqttServer.Stop();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            Console.ReadLine();
+        }
+    }
+}

Tests/MQTTnet.TestApp.NetFramework/MQTTnet.TestApp.NetFramework.csproj

@@ -82,6 +82,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="PerformanceTest.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
@@ -90,7 +91,7 @@
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\Frameworks\MQTTnet.NetFramework\MQTTnet.NetFramework.csproj">
-      <Project>{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}</Project>
+      <Project>{a480ef90-0eaa-4d9a-b271-47a9c47f6f7d}</Project>
       <Name>MQTTnet.NetFramework</Name>
     </ProjectReference>
     <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">

Tests/MQTTnet.TestApp.NetFramework/PerformanceTest.cs

@@ -0,0 +1,219 @@
+using MQTTnet.Core;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Packets;
+using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Server;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MQTTnet.TestApp.NetFramework
+{
+    public static class PerformanceTest
+    {
+        public static async Task RunAsync()
+        {
+            var server = Task.Factory.StartNew(RunServerAsync, TaskCreationOptions.LongRunning);
+            var client = Task.Factory.StartNew(() => RunClientAsync(2000, TimeSpan.FromMilliseconds(10)), TaskCreationOptions.LongRunning);
+
+            await Task.WhenAll(server, client).ConfigureAwait(false);
+        }
+
+        private static Task RunClientsAsync(int msgChunkSize, TimeSpan interval)
+        {
+            return Task.WhenAll(Enumerable.Range(0, 3).Select(i => Task.Run(() => RunClientAsync(msgChunkSize, interval))));
+        }
+
+        private static async Task RunClientAsync(int msgChunkSize, TimeSpan interval)
+        {
+            try
+            {
+                var options = new MqttClientOptions
+                {
+                    Server = "localhost",
+                    ClientId = "XYZ",
+                    CleanSession = true,
+                    DefaultCommunicationTimeout = TimeSpan.FromMinutes(10)
+                };
+
+                var client = new MqttClientFactory().CreateMqttClient(options);
+                client.ApplicationMessageReceived += (s, e) =>
+                {
+                };
+
+                client.Connected += async (s, e) =>
+                {
+                    Console.WriteLine("### CONNECTED WITH SERVER ###");
+
+                    await client.SubscribeAsync(new List<TopicFilter>
+                    {
+                        new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)
+                    });
+
+                    Console.WriteLine("### SUBSCRIBED ###");
+                };
+
+                client.Disconnected += async (s, e) =>
+                {
+                    Console.WriteLine("### DISCONNECTED FROM SERVER ###");
+                    await Task.Delay(TimeSpan.FromSeconds(5));
+
+                    try
+                    {
+                        await client.ConnectAsync();
+                    }
+                    catch
+                    {
+                        Console.WriteLine("### RECONNECTING FAILED ###");
+                    }
+                };
+
+                try
+                {
+                    await client.ConnectAsync();
+                }
+                catch (Exception exception)
+                {
+                    Console.WriteLine("### CONNECTING FAILED ###" + Environment.NewLine + exception);
+                }
+
+                Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
+
+                var testMessageCount = 10000;
+                var message = CreateMessage();
+                var stopwatch = Stopwatch.StartNew();
+                for (var i = 0; i < testMessageCount; i++)
+                {
+                    await client.PublishAsync(message);
+                }
+
+                stopwatch.Stop();
+                Console.WriteLine($"Sent 10.000 messages within {stopwatch.ElapsedMilliseconds} ms ({stopwatch.ElapsedMilliseconds / (float)testMessageCount} ms / message).");
+
+                stopwatch.Restart();
+                var sentMessagesCount = 0;
+                while (stopwatch.ElapsedMilliseconds < 1000)
+                {
+                    await client.PublishAsync(message);
+                    sentMessagesCount++;
+                }
+
+                Console.WriteLine($"Sending {sentMessagesCount} messages per second.");
+
+                var last = DateTime.Now;
+                var msgCount = 0;
+
+                while (true)
+                {
+                    var msgs = Enumerable.Range(0, msgChunkSize)
+                        .Select(i => CreateMessage())
+                        .ToList();
+
+                    if (true)
+                    {
+                        //send concurrent (test for raceconditions)
+                        var sendTasks = msgs
+                            .Select(msg => PublishSingleMessage(client, msg, ref msgCount))
+                            .ToList();
+
+                        await Task.WhenAll(sendTasks);
+                    }
+                    else
+                    {
+                        await client.PublishAsync(msgs);
+                        msgCount += msgs.Count;
+                        //send multiple
+                    }
+
+
+
+                    var now = DateTime.Now;
+                    if (last < now - TimeSpan.FromSeconds(1))
+                    {
+                        Console.WriteLine($"sending {msgCount} intended {msgChunkSize / interval.TotalSeconds}");
+                        msgCount = 0;
+                        last = now;
+                    }
+
+                    await Task.Delay(interval).ConfigureAwait(false);
+                }
+            }
+            catch (Exception exception)
+            {
+                Console.WriteLine(exception);
+            }
+        }
+
+        private static MqttApplicationMessage CreateMessage()
+        {
+            return new MqttApplicationMessage(
+                "A/B/C",
+                Encoding.UTF8.GetBytes("Hello World"),
+                MqttQualityOfServiceLevel.AtMostOnce,
+                false
+            );
+        }
+
+        private static Task PublishSingleMessage(IMqttClient client, MqttApplicationMessage applicationMessage, ref int count)
+        {
+            Interlocked.Increment(ref count);
+            return Task.Run(() =>
+           {
+               return client.PublishAsync(applicationMessage);
+           });
+        }
+
+        private static void RunServerAsync()
+        {
+            try
+            {
+                var options = new MqttServerOptions
+                {
+                    ConnectionValidator = p =>
+                    {
+                        if (p.ClientId == "SpecialClient")
+                        {
+                            if (p.Username != "USER" || p.Password != "PASS")
+                            {
+                                return MqttConnectReturnCode.ConnectionRefusedBadUsernameOrPassword;
+                            }
+                        }
+
+                        return MqttConnectReturnCode.ConnectionAccepted;
+                    },
+                    DefaultCommunicationTimeout = TimeSpan.FromMinutes(10)
+                };
+
+                var mqttServer = new MqttServerFactory().CreateMqttServer(options);
+                var msgs = 0;
+                var stopwatch = Stopwatch.StartNew();
+                mqttServer.ApplicationMessageReceived += (sender, args) =>
+                {
+                    msgs++;
+                    if (stopwatch.ElapsedMilliseconds > 1000)
+                    {
+                        Console.WriteLine($"received {msgs}");
+                        msgs = 0;
+                        stopwatch.Restart();
+                    }
+                };
+                mqttServer.Start();
+
+                Console.WriteLine("Press any key to exit.");
+                Console.ReadLine();
+
+                mqttServer.Stop();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            Console.ReadLine();
+        }
+    }
+}

Tests/MQTTnet.TestApp.NetFramework/Program.cs

@@ -19,6 +19,7 @@ namespace MQTTnet.TestApp.NetFramework
             Console.WriteLine("MQTTnet - TestApp.NetFramework");
             Console.WriteLine("1 = Start client");
             Console.WriteLine("2 = Start server");
+            Console.WriteLine("3 = Start performance test");
             var pressedKey = Console.ReadKey(true);
             if (pressedKey.Key == ConsoleKey.D1)
             {
@@ -30,10 +31,16 @@ namespace MQTTnet.TestApp.NetFramework
                 Task.Run(() => RunServerAsync(args));
                 Thread.Sleep(Timeout.Infinite);
             }
+            else if (pressedKey.Key == ConsoleKey.D3)
+            {
+                Task.Run(PerformanceTest.RunAsync);
+                Thread.Sleep(Timeout.Infinite);
+            }
         }
 
         private static async Task RunClientAsync(string[] arguments)
         {
+
             MqttTrace.TraceMessagePublished += (s, e) =>
             {
                 Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
@@ -71,8 +78,6 @@ namespace MQTTnet.TestApp.NetFramework
                     {
                         new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)
                     });
-
-                    Console.WriteLine("### SUBSCRIBED ###");
                 };
 
                 client.Disconnected += async (s, e) =>
@@ -101,17 +106,12 @@ namespace MQTTnet.TestApp.NetFramework
 
                 Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
 
+                var messageFactory = new MqttApplicationMessageFactory();
                 while (true)
                 {
                     Console.ReadLine();
 
-                    var applicationMessage = new MqttApplicationMessage(
-                        "A/B/C",
-                        Encoding.UTF8.GetBytes("Hello World"),
-                        MqttQualityOfServiceLevel.AtLeastOnce,
-                        false
-                    );
-
+                    var applicationMessage = messageFactory.CreateApplicationMessage("myTopic", "Hello World", MqttQualityOfServiceLevel.AtLeastOnce);
                     await client.PublishAsync(applicationMessage);
                 }
             }

Tests/MQTTnet.TestApp.UniversalWindows/App.xaml

@@ -2,7 +2,5 @@
     x:Class="MQTTnet.TestApp.UniversalWindows.App"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:local="using:MQTTnet.TestApp.UniversalWindows"
     RequestedTheme="Light">
-
 </Application>

Tests/MQTTnet.TestApp.UniversalWindows/MQTTnet.TestApp.UniversalWindows.csproj

@@ -18,7 +18,7 @@
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <WindowsXamlEnableOverview>true</WindowsXamlEnableOverview>
     <PackageCertificateKeyFile>MQTTnet.TestApp.UniversalWindows_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>C5051872F588878B167FB976FDF249518AA2DDF0</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>13E377A693C923EE9E88EE84B32A4B9881657362</PackageCertificateThumbprint>
     <RuntimeIdentifiers>win10;win10-arm;win10-arm-aot;win10-x86;win10-x86-aot;win10-x64;win10-x64-aot</RuntimeIdentifiers>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
@@ -42,7 +42,7 @@
     <UseVSHostingProcess>false</UseVSHostingProcess>
     <ErrorReport>prompt</ErrorReport>
     <Prefer32Bit>true</Prefer32Bit>
-    <UseDotNetNativeToolchain>true</UseDotNetNativeToolchain>
+    <UseDotNetNativeToolchain>false</UseDotNetNativeToolchain>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|ARM'">
     <DebugSymbols>true</DebugSymbols>
@@ -137,7 +137,10 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
-      <Version>5.3.3</Version>
+      <Version>5.4.0</Version>
+    </PackageReference>
+    <PackageReference Include="Microsoft.Toolkit.Uwp.UI.Controls">
+      <Version>2.0.0</Version>
     </PackageReference>
   </ItemGroup>
   <PropertyGroup Condition=" '$(VisualStudioVersion)' == '' or '$(VisualStudioVersion)' &lt; '14.0' ">

Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml

@@ -2,9 +2,10 @@
     x:Class="MQTTnet.TestApp.UniversalWindows.MainPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:local="using:MQTTnet.TestApp.UniversalWindows"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    d:DesignHeight="800"
+    d:DesignWidth="800"
     mc:Ignorable="d">
 
     <Grid Margin="10">
@@ -12,28 +13,86 @@
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto" />
             <RowDefinition Height="*" />
+            <RowDefinition Height="Auto" />
         </Grid.RowDefinitions>
 
-        <StackPanel Grid.Row="0" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
-            <TextBlock>Server:</TextBlock>
-            <TextBox x:Name="Server"></TextBox>
-            <TextBlock>User:</TextBlock>
-            <TextBox x:Name="User"></TextBox>
-            <TextBlock>Password:</TextBlock>
-            <TextBox x:Name="Password"></TextBox>
-            <TextBlock>ClientId:</TextBlock>
-            <TextBox x:Name="ClientId"></TextBox>
+        <Pivot Grid.Row="0" >
+            <PivotItem Header="Connection">
+                <StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+                    <TextBlock>Server:</TextBlock>
+                    <TextBox x:Name="Server"></TextBox>
+                    <TextBlock>User:</TextBlock>
+                    <TextBox x:Name="User"></TextBox>
+                    <TextBlock>Password:</TextBlock>
+                    <TextBox x:Name="Password"></TextBox>
+                    <TextBlock>ClientId:</TextBlock>
+                    <TextBox x:Name="ClientId"></TextBox>
 
-            <CheckBox x:Name="UseTls">Use TLS</CheckBox>
-            <Button Click="Connect">Connect</Button>
-            <TextBlock>Trace:</TextBlock>
-        </StackPanel>
+                    <StackPanel Orientation="Horizontal">
+                        <RadioButton x:Name="UseTcp" IsChecked="True" GroupName="connection">TCP</RadioButton>
+                        <RadioButton x:Name="UseWs" GroupName="connection">WS</RadioButton>
+                        <CheckBox x:Name="UseTls">Use TLS</CheckBox>
+                    </StackPanel>
 
+                    <StackPanel Orientation="Horizontal">
+                        <Button Click="Connect" Width="120" Margin="0,0,10,0">Connect</Button>
+                        <Button Click="Disconnect" Width="120">Disconnect</Button>
+                    </StackPanel>
+                </StackPanel>
 
-        <ScrollViewer Grid.Row="1" Background="Black" Foreground="WhiteSmoke" FontFamily="Consolas" HorizontalScrollMode="Enabled" VerticalScrollMode="Enabled" HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Visible">
-            <TextBlock x:Name="Trace"></TextBlock>
+            </PivotItem>
+            <PivotItem Header="Publish">
+                <StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+                    <TextBlock>Topic:</TextBlock>
+                    <TextBox x:Name="Topic"></TextBox>
+
+                    <TextBlock>Payload:</TextBlock>
+                    <TextBox x:Name="Payload"></TextBox>
+                    <StackPanel Orientation="Horizontal">
+                        <RadioButton x:Name="Text" IsChecked="True" GroupName="payload">Text</RadioButton>
+                        <RadioButton x:Name="Base64" GroupName="payload">Base64</RadioButton>
+                    </StackPanel>
+
+                    <TextBlock>Retain:</TextBlock>
+                    <CheckBox x:Name="Retain"></CheckBox>
+
+                    <TextBlock>QoS:</TextBlock>
+                    <StackPanel Orientation="Horizontal">
+                        <RadioButton Margin="0,0,10,0" x:Name="QoS0" IsChecked="True" GroupName="qos">0 (At most once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" x:Name="QoS1" GroupName="qos">1 (At least once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" x:Name="QoS2" GroupName="qos">2 (Exactly once)</RadioButton>
+                    </StackPanel>
+                    <Button Click="Publish" Width="120">Publish</Button>
+                </StackPanel>
+            </PivotItem>
+
+            <PivotItem Header="Subscribe">
+                <StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+                    <TextBlock>Topic:</TextBlock>
+                    <TextBox x:Name="SubscribeTopic"></TextBox>
+
+                    <TextBlock>QoS:</TextBlock>
+                    <StackPanel Orientation="Horizontal">
+                        <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS0" IsChecked="True" GroupName="sqos">0 (At most once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS1" GroupName="sqos">1 (At least once)</RadioButton>
+                        <RadioButton Margin="0,0,10,0" x:Name="SubscribeQoS2" GroupName="sqos">2 (Exactly once)</RadioButton>
+                    </StackPanel>
+
+                    <StackPanel Orientation="Horizontal">
+                        <Button Click="Subscribe" Width="120" Margin="0,0,10,0">Subscribe</Button>
+                        <Button Click="Unsubscribe" Width="120">Unsubscribe</Button>
+                    </StackPanel>
+                </StackPanel>
+            </PivotItem>
+        </Pivot>
+
+        <ScrollViewer Margin="12,10,12,0" Grid.Row="1" Background="Black" Foreground="WhiteSmoke" FontFamily="Consolas" HorizontalScrollMode="Enabled" VerticalScrollMode="Enabled" HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Visible">
+            <TextBlock x:Name="Trace" FontSize="11"></TextBlock>
         </ScrollViewer>
 
+        <StackPanel Margin="12,0,12,10" Grid.Row="2">
+            <Button Click="Clear" Width="120">Clear</Button>
+        </StackPanel>
     </Grid>
 
 </Page>

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

@@ -1,8 +1,12 @@
 using System;
+using System.Text;
 using Windows.UI.Core;
 using Windows.UI.Xaml;
+using MQTTnet.Core;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Packets;
+using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.TestApp.UniversalWindows
 {
@@ -21,7 +25,7 @@ namespace MQTTnet.TestApp.UniversalWindows
         {
             await Trace.Dispatcher.RunAsync(CoreDispatcherPriority.High, () =>
             {
-                var text = $"[{DateTime.Now:O}] [{e.Level}] [{e.Source}] [{e.ThreadId}] [{e.Message}]{Environment.NewLine}";
+                var text = $"[{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}] [{e.Level}] [{e.Source}] [{e.ThreadId}] [{e.Message}]{Environment.NewLine}";
                 if (e.Exception != null)
                 {
                     text += $"{e.Exception}{Environment.NewLine}";
@@ -38,11 +42,11 @@ namespace MQTTnet.TestApp.UniversalWindows
                 Server = Server.Text,
                 UserName = User.Text,
                 Password = Password.Text,
-                ClientId = ClientId.Text
+                ClientId = ClientId.Text,
+                TlsOptions = { UseTls = UseTls.IsChecked == true },
+                ConnectionType = UseTcp.IsChecked == true ? MqttConnectionType.Tcp : MqttConnectionType.Ws
             };
-
-            options.TlsOptions.UseTls = UseTls.IsChecked == true;
-
+            
             try
             {
                 if (_mqttClient != null)
@@ -59,5 +63,112 @@ namespace MQTTnet.TestApp.UniversalWindows
                 Trace.Text += exception + Environment.NewLine;
             }
         }
+
+        private async void Publish(object sender, RoutedEventArgs e)
+        {
+            if (_mqttClient == null)
+            {
+                return;
+            }
+
+            try
+            {
+                var qos = MqttQualityOfServiceLevel.AtMostOnce;
+                if (QoS1.IsChecked == true)
+                {
+                    qos = MqttQualityOfServiceLevel.AtLeastOnce;
+                }
+
+                if (QoS2.IsChecked == true)
+                {
+                    qos = MqttQualityOfServiceLevel.ExactlyOnce;
+                }
+
+                var payload = new byte[0];
+                if (Text.IsChecked == true)
+                {
+                    payload = Encoding.UTF8.GetBytes(Payload.Text);
+                }
+
+                if (Base64.IsChecked == true)
+                {
+                    payload = Convert.FromBase64String(Payload.Text);
+                }
+
+                var message = new MqttApplicationMessage(
+                    Topic.Text,
+                    payload,
+                    qos,
+                    Retain.IsChecked == true);
+
+                await _mqttClient.PublishAsync(message);
+            }
+            catch (Exception exception)
+            {
+                Trace.Text += exception + Environment.NewLine;
+            }
+        }
+
+        private async void Disconnect(object sender, RoutedEventArgs e)
+        {
+            try
+            {
+                await _mqttClient.DisconnectAsync();
+            }
+            catch (Exception exception)
+            {
+                Trace.Text += exception + Environment.NewLine;
+            }
+        }
+
+        private void Clear(object sender, RoutedEventArgs e)
+        {
+            Trace.Text = string.Empty;
+        }
+
+        private async void Subscribe(object sender, RoutedEventArgs e)
+        {
+            if (_mqttClient == null)
+            {
+                return;
+            }
+
+            try
+            {
+                var qos = MqttQualityOfServiceLevel.AtMostOnce;
+                if (SubscribeQoS1.IsChecked == true)
+                {
+                    qos = MqttQualityOfServiceLevel.AtLeastOnce;
+                }
+
+                if (SubscribeQoS2.IsChecked == true)
+                {
+                    qos = MqttQualityOfServiceLevel.ExactlyOnce;
+                }
+
+                await _mqttClient.SubscribeAsync(new TopicFilter(SubscribeTopic.Text, qos));
+            }
+            catch (Exception exception)
+            {
+                Trace.Text += exception + Environment.NewLine;
+            }
+        }
+
+        private async void Unsubscribe(object sender, RoutedEventArgs e)
+        {
+            if (_mqttClient == null)
+            {
+                return;
+            }
+
+            try
+            {
+                await _mqttClient.UnsubscribeAsync(SubscribeTopic.Text);
+            }
+            catch (Exception exception)
+            {
+                Trace.Text += exception + Environment.NewLine;
+            }
+        }
     }
 }

Tests/MQTTnet.TestApp.UniversalWindows/Package.appxmanifest

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Package xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10" xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest" xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10" IgnorableNamespaces="uap mp">
+<Package xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10" xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest" xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10" xmlns:uap3="http://schemas.microsoft.com/appx/manifest/uap/windows10/3" IgnorableNamespaces="uap mp uap3">
   <Identity Name="4fa21172-9128-4e84-8a6d-74b9acde4d58" Publisher="CN=Christian" Version="1.0.0.0" />
   <mp:PhoneIdentity PhoneProductId="4fa21172-9128-4e84-8a6d-74b9acde4d58" PhonePublisherId="00000000-0000-0000-0000-000000000000" />
   <Properties>
@@ -15,7 +15,7 @@
   </Resources>
   <Applications>
     <Application Id="App" Executable="$targetnametoken$.exe" EntryPoint="MQTTnet.TestApp.UniversalWindows.App">
-      <uap:VisualElements DisplayName="MQTTnet.TestApp.UniversalWindows" Square150x150Logo="Assets\Square150x150Logo.png" Square44x44Logo="Assets\Square44x44Logo.png" Description="MQTTnet.TestApp.UniversalWindows" BackgroundColor="transparent">
+      <uap:VisualElements DisplayName="MQTTnet Test App" Square150x150Logo="Assets\Square150x150Logo.png" Square44x44Logo="Assets\Square44x44Logo.png" Description="Test application for MQTT based communication" BackgroundColor="transparent">
         <uap:DefaultTile Wide310x150Logo="Assets\Wide310x150Logo.png">
         </uap:DefaultTile>
         <uap:SplashScreen Image="Assets\SplashScreen.png" />
@@ -24,5 +24,7 @@
   </Applications>
   <Capabilities>
     <Capability Name="internetClient" />
+    <Capability Name="internetClientServer" />
+    <Capability Name="privateNetworkClientServer" />
   </Capabilities>
 </Package>