Fix several bugs

Fix50 eventing

.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>2.2.1</version>
+    <version>2.4.0</version>
     <authors>Christian Kratky</authors>
     <owners>Christian Kratky</owners>
     <licenseUrl>https://github.com/chkr1011/MQTTnet/blob/master/LICENSE</licenseUrl>
@@ -10,19 +10,29 @@
     <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 a bug in connection management (Thanks to rydergillen-compacSort)
+    <releaseNotes>* [Server] Added an event which is fired when a client has disconnected.
+* [Server] Added support for retained application messages
+* [Server] Added support for saving and loading retained messages
+* [Server] The client connection is now closed if sending of one pending application message has failed
+* [Server] Fixed handling of _Dup_ flag (Thanks to haeberle)
+* [Core] Optimized exception handling
+* [Core] Mono is now also supported (Thanks to JTrotta)
+* [Client] The options are now passed in _ConnectAsync_ (Breaking change! Read Wiki for examples)
+* [Core] Trace class renamed to _MqttNetTrace_ (Breaking change!)
+* [Client] Extended certificate validation options (Breaking change!)
+* [Client] Added static certificate validation callback (NetFramework, NetStandard) / ignorable certificate errors (UniversalWindows) to _MqttTcpChannel_
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2017</copyright>
-    <tags>MQTT MQTTClient MQTTServer MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Queue Hardware Arduino</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/MqttCommunicationAdapterFactory.cs

@@ -0,0 +1,27 @@
+using System;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
+    {
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (options is MqttClientTcpOptions tcpOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttTcpChannel(tcpOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            if (options is MqttClientWebSocketOptions webSocketOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttWebSocketChannel(webSocketOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.NetFramework/Implementations/MqttServerAdapter.cs

@@ -22,9 +22,9 @@ namespace MQTTnet.Implementations
 
         private bool _isRunning;
 
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        public event Action<IMqttCommunicationAdapter> ClientAccepted;
 
-        public void Start(MqttServerOptions options)
+        public Task StartAsync(MqttServerOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 
@@ -57,9 +57,11 @@ namespace MQTTnet.Implementations
 
                 Task.Run(() => AcceptTlsEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
             }
+
+            return Task.FromResult(0);
         }
 
-        public void Stop()
+        public Task StopAsync()
         {
             _isRunning = false;
 
@@ -72,11 +74,13 @@ namespace MQTTnet.Implementations
 
             _tlsEndpointSocket?.Dispose();
             _tlsEndpointSocket = null;
+
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
-            Stop();
+            StopAsync();
         }
 
         private async Task AcceptDefaultEndpointConnectionsAsync(CancellationToken cancellationToken)
@@ -85,16 +89,18 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null);
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, null), new MqttPacketSerializer());
-                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                    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());
+                    ClientAccepted?.Invoke(clientAdapter);
                 }
                 catch (Exception exception) when (!(exception is ObjectDisposedException))
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
+                    MqttNetTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
 
                     //excessive CPU consumed if in endless loop of socket errors
-                    Thread.Sleep(TimeSpan.FromSeconds(1));
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }
@@ -105,20 +111,21 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await Task.Factory.FromAsync(_tlsEndpointSocket.BeginAccept, _tlsEndpointSocket.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 MqttPacketSerializer());
-                    ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
+                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false).ConfigureAwait(false);
+
+                    var tcpChannel = new MqttTcpChannel(clientSocket, sslStream);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(tcpChannel, new MqttPacketSerializer());
+                    ClientAccepted?.Invoke(clientAdapter);
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
+                    MqttNetTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
 
                     //excessive CPU consumed if in endless loop of socket errors
-                    Thread.Sleep(TimeSpan.FromSeconds(1));
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }

Frameworks/MQTTnet.NetFramework/Implementations/MqttTcpChannel.cs

@@ -6,116 +6,131 @@ using System.Security.Cryptography.X509Certificates;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
+using System.IO;
+using System.Linq;
 
 namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
+        private readonly MqttClientTcpOptions _options;
+
+        // 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;
 
-        public MqttTcpChannel()
+        /// <summary>
+        /// called on client sockets are created in connect
+        /// </summary>
+        public MqttTcpChannel(MqttClientTcpOptions options)
         {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
+        /// <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 async Task ConnectAsync(MqttClientOptions options)
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream { get; private set; }
+
+        public static Func<X509Certificate, X509Chain, SslPolicyErrors, MqttClientTcpOptions, bool> CustomCertificateValidationCallback { get; set; }
+
+        public async Task ConnectAsync()
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-            try
+            if (_socket == null)
             {
-                if (_socket == null)
-                {
-                    _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-                }
-
-                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);
-                }
+                _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
             }
-            catch (SocketException exception)
+
+            await Task.Factory.FromAsync(_socket.BeginConnect, _socket.EndConnect, _options.Server, _options.GetPort(), null).ConfigureAwait(false);
+
+            if (_options.TlsOptions.UseTls)
             {
-                throw new MqttCommunicationException(exception);
+                _sslStream = new SslStream(new NetworkStream(_socket, true), false, InternalUserCertificateValidationCallback);
+                await _sslStream.AuthenticateAsClientAsync(_options.Server, LoadCertificates(_options), SslProtocols.Tls12, _options.TlsOptions.IgnoreCertificateRevocationErrors).ConfigureAwait(false);
             }
+
+            CreateStreams(_socket, _sslStream);
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                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()
         {
-            _socket?.Dispose();
-            _sslStream?.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 bool InternalUserCertificateValidationCallback(object sender, X509Certificate x509Certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
+        {
+            if (CustomCertificateValidationCallback != null)
+            {
+                return CustomCertificateValidationCallback(x509Certificate, chain, sslPolicyErrors, _options);
+            }
+
+            if (sslPolicyErrors == SslPolicyErrors.None)
+            {
+                return true;
+            }
+
+            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.RevocationStatusUnknown || c.Status == X509ChainStatusFlags.Revoked || c.Status == X509ChainStatusFlags.RevocationStatusUnknown))
+            {
+                if (!_options.TlsOptions.IgnoreCertificateRevocationErrors)
+                {
+                    return false;
+                }
+            }
+
+            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.PartialChain))
+            {
+                if (!_options.TlsOptions.IgnoreCertificateChainErrors)
+                {
+                    return false;
+                }
+            }
+            
+            return _options.TlsOptions.AllowUntrustedCertificates;
+        }
+
         private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
         {
             var certificates = new X509CertificateCollection();

Frameworks/MQTTnet.NetFramework/Implementations/MqttWebSocketChannel.cs

@@ -0,0 +1,57 @@
+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 readonly MqttClientWebSocketOptions _options;
+
+        private ClientWebSocket _webSocket;
+
+        public MqttWebSocketChannel(MqttClientWebSocketOptions options)
+        {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public Stream RawReceiveStream { get; private set; }
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+        
+        public async Task ConnectAsync()
+        {
+            var uri = _options.Uri;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+ 
+            _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 +100,9 @@
     <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Implementations\MqttCommunicationAdapterFactory.cs" />
+    <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 +1,13 @@
-using System;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Client;
-using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Client;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
-        public IMqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient()
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttPacketSerializer()));
+            return new MqttClient(new MqttCommunicationAdapterFactory());
         }
     }
 }

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("2.2.1.0")]
-[assembly: AssemblyFileVersion("2.2.1.0")]
+[assembly: AssemblyVersion("2.4.0.0")]
+[assembly: AssemblyFileVersion("2.4.0.0")]

Frameworks/MQTTnet.NetStandard/Implementations/MqttCommunicationAdapterFactory.cs

@@ -0,0 +1,27 @@
+using System;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
+    {
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (options is MqttClientTcpOptions tcpOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttTcpChannel(tcpOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            if (options is MqttClientWebSocketOptions webSocketOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttWebSocketChannel(webSocketOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/Implementations/MqttServerAdapter.cs

@@ -22,11 +22,12 @@ namespace MQTTnet.Implementations
 
         private bool _isRunning;
 
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        public event Action<IMqttCommunicationAdapter> ClientAccepted;
 
-        public void Start(MqttServerOptions options)
+        public Task StartAsync(MqttServerOptions options)
         {
             if (_isRunning) throw new InvalidOperationException("Server is already started.");
+
             _isRunning = true;
 
             _cancellationTokenSource = new CancellationTokenSource();
@@ -55,9 +56,11 @@ namespace MQTTnet.Implementations
 
                 Task.Run(() => AcceptTlsEndpointConnectionsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
             }
+
+            return Task.FromResult(0);
         }
 
-        public void Stop()
+        public Task StopAsync()
         {
             _isRunning = false;
 
@@ -70,11 +73,13 @@ namespace MQTTnet.Implementations
 
             _tlsEndpointSocket?.Dispose();
             _tlsEndpointSocket = null;
+
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
-            Stop();
+            StopAsync();
         }
 
         private async Task AcceptDefaultEndpointConnectionsAsync(CancellationToken cancellationToken)
@@ -83,16 +88,16 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await _defaultEndpointSocket.AcceptAsync();
+                    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));
+                    ClientAccepted?.Invoke(clientAdapter);
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
+                    MqttNetTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
 
                     //excessive CPU consumed if in endless loop of socket errors
-                    Thread.Sleep(TimeSpan.FromSeconds(1));
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }
@@ -103,20 +108,20 @@ namespace MQTTnet.Implementations
             {
                 try
                 {
-                    var clientSocket = await _tlsEndpointSocket.AcceptAsync();
+                    var clientSocket = await _tlsEndpointSocket.AcceptAsync().ConfigureAwait(false);
 
                     var sslStream = new SslStream(new NetworkStream(clientSocket));
-                    await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false);
-                    
+                    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));
+                    ClientAccepted?.Invoke(clientAdapter);
                 }
                 catch (Exception exception)
                 {
-                    MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
+                    MqttNetTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at TLS endpoint.");
 
                     //excessive CPU consumed if in endless loop of socket errors
-                    Thread.Sleep(TimeSpan.FromSeconds(1));
+                    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
                 }
             }
         }

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs

@@ -6,109 +6,110 @@ using System.Security.Cryptography.X509Certificates;
 using System.Threading.Tasks;
 using MQTTnet.Core.Channel;
 using MQTTnet.Core.Client;
-using MQTTnet.Core.Exceptions;
+using System.IO;
+using System.Linq;
 
 namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
+        private readonly MqttClientTcpOptions _options;
+
         private Socket _socket;
         private SslStream _sslStream;
-
-        public MqttTcpChannel()
+        
+        /// <summary>
+        /// called on client sockets are created in connect
+        /// </summary>
+        public MqttTcpChannel(MqttClientTcpOptions options)
         {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
+        /// <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 async Task ConnectAsync(MqttClientOptions options)
-        {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-            try
-            {
-                if (_socket == null)
-                {
-                    _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
-                }
+        public Stream SendStream => ReceiveStream;
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream => ReceiveStream;
 
-                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);
-                }
-            }
-            catch (SocketException exception)
+        public static Func<X509Certificate, X509Chain, SslPolicyErrors, MqttClientTcpOptions, bool> CustomCertificateValidationCallback { get; set; }
+
+        public async Task ConnectAsync()
+        {
+            if (_socket == null)
             {
-                throw new MqttCommunicationException(exception);
+                _socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+            }
+
+            await _socket.ConnectAsync(_options.Server, _options.GetPort()).ConfigureAwait(false);
+
+            if (_options.TlsOptions.UseTls)
+            {
+                _sslStream = new SslStream(new NetworkStream(_socket, true), false, InternalUserCertificateValidationCallback);
+                ReceiveStream = _sslStream;
+                await _sslStream.AuthenticateAsClientAsync(_options.Server, LoadCertificates(_options), SslProtocols.Tls12, _options.TlsOptions.IgnoreCertificateRevocationErrors).ConfigureAwait(false);
+            }
+            else
+            {
+                ReceiveStream = new NetworkStream(_socket);
             }
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                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();
-            _sslStream?.Dispose();
-
             _socket = null;
+
+            _sslStream?.Dispose();
             _sslStream = null;
         }
 
+        private bool InternalUserCertificateValidationCallback(object sender, X509Certificate x509Certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
+        {
+            if (CustomCertificateValidationCallback != null)
+            {
+                return CustomCertificateValidationCallback(x509Certificate, chain, sslPolicyErrors, _options);
+            }
+
+            if (sslPolicyErrors == SslPolicyErrors.None)
+            {
+                return true;
+            }
+
+            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.RevocationStatusUnknown || c.Status == X509ChainStatusFlags.Revoked || c.Status == X509ChainStatusFlags.RevocationStatusUnknown))
+            {
+                if (!_options.TlsOptions.IgnoreCertificateRevocationErrors)
+                {
+                    return false;
+                }
+            }
+
+            if (chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.PartialChain))
+            {
+                if (!_options.TlsOptions.IgnoreCertificateChainErrors)
+                {
+                    return false;
+                }
+            }
+
+            return _options.TlsOptions.AllowUntrustedCertificates;
+        }
+
         private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
         {
             var certificates = new X509CertificateCollection();

Frameworks/MQTTnet.NetStandard/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 readonly MqttClientWebSocketOptions _options;
+        private ClientWebSocket _webSocket;
+
+        public MqttWebSocketChannel(MqttClientWebSocketOptions options)
+        {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+        public Stream RawReceiveStream { get; private set; }
+
+        public async Task ConnectAsync()
+        {
+            var uri = _options.Uri;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+
+            _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>2.2.1.0</AssemblyVersion>
-    <FileVersion>2.2.1.0</FileVersion>
+    <AssemblyVersion>2.4.0.0</AssemblyVersion>
+    <FileVersion>2.4.0.0</FileVersion>
     <Version>0.0.0.0</Version>
     <Company />
     <Product />
@@ -23,7 +23,9 @@
   </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>
 

Frameworks/MQTTnet.NetStandard/MqttClientFactory.cs

@@ -1,18 +1,13 @@
-using System;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Client;
-using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Client;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
-        public IMqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient()
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttPacketSerializer()));
+            return new MqttClient(new MqttCommunicationAdapterFactory());
         }
     }
-}
+}

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/MqttCommunicationAdapterFactory.cs

@@ -0,0 +1,27 @@
+using System;
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Serializer;
+
+namespace MQTTnet.Implementations
+{
+    public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
+    {
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (options is MqttClientTcpOptions tcpOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttTcpChannel(tcpOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            if (options is MqttClientWebSocketOptions webSocketOptions)
+            {
+                return new MqttChannelCommunicationAdapter(new MqttWebSocketChannel(webSocketOptions), new MqttPacketSerializer { ProtocolVersion = options.ProtocolVersion });
+            }
+
+            throw new NotSupportedException();
+        }
+    }
+}

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttServerAdapter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Serializer;
@@ -10,23 +11,24 @@ namespace MQTTnet.Implementations
     public class MqttServerAdapter : IMqttServerAdapter, IDisposable
     {
         private StreamSocketListener _defaultEndpointSocket;
-        
+
         private bool _isRunning;
 
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        public event Action<IMqttCommunicationAdapter> ClientAccepted;
 
-        public void Start(MqttServerOptions options)
+        public async Task StartAsync(MqttServerOptions options)
         {
             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;                
+                await _defaultEndpointSocket.BindServiceNameAsync(options.GetDefaultEndpointPort().ToString(), SocketProtectionLevel.PlainSocket);
+                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;
             }
 
             if (options.TlsEndpointOptions.IsEnabled)
@@ -35,17 +37,19 @@ namespace MQTTnet.Implementations
             }
         }
 
-        public void Stop()
+        public Task StopAsync()
         {
             _isRunning = false;
 
             _defaultEndpointSocket?.Dispose();
             _defaultEndpointSocket = null;
+
+            return Task.FromResult(0);
         }
 
         public void Dispose()
         {
-            Stop();
+            StopAsync();
         }
 
         private void AcceptDefaultEndpointConnectionsAsync(StreamSocketListener sender, StreamSocketListenerConnectionReceivedEventArgs args)
@@ -53,11 +57,11 @@ namespace MQTTnet.Implementations
             try
             {
                 var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(args.Socket), new MqttPacketSerializer());
-                ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(args.Socket.Information.RemoteAddress.ToString(), clientAdapter));
+                ClientAccepted?.Invoke(clientAdapter);
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
+                MqttNetTrace.Error(nameof(MqttServerAdapter), exception, "Error while accepting connection at default endpoint.");
             }
         }
     }

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttTcpChannel.cs

@@ -1,113 +1,94 @@
 using System;
+using System.Collections.Generic;
+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 MqttClientTcpOptions _options;
         private StreamSocket _socket;
 
-        public MqttTcpChannel()
+        public MqttTcpChannel(MqttClientTcpOptions options)
         {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
         public MqttTcpChannel(StreamSocket socket)
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
+
+            CreateStreams();
         }
 
-        public async Task ConnectAsync(MqttClientOptions options)
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawReceiveStream { get; private set; }
+
+        public static Func<MqttClientTcpOptions, IEnumerable<ChainValidationResult>> CustomIgnorableServerCertificateErrorsResolver { get; set; }
+
+        public async Task ConnectAsync()
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-            try
+            if (_socket == null)
             {
-                if (_socket == null)
-                {
-                    _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);
-                }
+                _socket = new StreamSocket();
             }
-            catch (SocketException exception)
+
+            if (!_options.TlsOptions.UseTls)
             {
-                throw new MqttCommunicationException(exception);
+                await _socket.ConnectAsync(new HostName(_options.Server), _options.GetPort().ToString());
             }
+            else
+            {
+                _socket.Control.ClientCertificate = LoadCertificate(_options);
+
+                foreach (var ignorableChainValidationResult in ResolveIgnorableServerCertificateErrors())
+                {
+                    _socket.Control.IgnorableServerCertificateErrors.Add(ignorableChainValidationResult);
+                }
+
+                await _socket.ConnectAsync(new HostName(_options.Server), _options.GetPort().ToString(), SocketProtectionLevel.Tls12);
+            }
+
+            CreateStreams();
         }
 
         public Task DisconnectAsync()
         {
-            try
-            {
-                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()
         {
-            _socket?.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)
         {
             if (options.TlsOptions.Certificates == null || !options.TlsOptions.Certificates.Any())
@@ -122,5 +103,34 @@ namespace MQTTnet.Implementations
 
             return new Certificate(options.TlsOptions.Certificates.First().AsBuffer());
         }
+
+        private IEnumerable<ChainValidationResult> ResolveIgnorableServerCertificateErrors()
+        {
+            if (CustomIgnorableServerCertificateErrorsResolver != null)
+            {
+                return CustomIgnorableServerCertificateErrorsResolver(_options);
+            }
+
+            var result = new List<ChainValidationResult>();
+
+            if (_options.TlsOptions.IgnoreCertificateRevocationErrors)
+            {
+                result.Add(ChainValidationResult.RevocationInformationMissing);
+                //_socket.Control.IgnorableServerCertificateErrors.Add(ChainValidationResult.Revoked); Not supported.
+                result.Add(ChainValidationResult.RevocationFailure);
+            }
+
+            if (_options.TlsOptions.IgnoreCertificateChainErrors)
+            {
+                result.Add(ChainValidationResult.IncompleteChain);
+            }
+
+            if (_options.TlsOptions.AllowUntrustedCertificates)
+            {
+                result.Add(ChainValidationResult.Untrusted);
+            }
+
+            return result;
+        }
     }
 }

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttWebSocketChannel.cs

@@ -0,0 +1,57 @@
+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 readonly MqttClientWebSocketOptions _options;
+        private ClientWebSocket _webSocket = new ClientWebSocket();
+
+        public MqttWebSocketChannel(MqttClientWebSocketOptions options)
+        {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public Stream RawReceiveStream { get; private set; }
+        public Stream SendStream => RawReceiveStream;
+        public Stream ReceiveStream => RawReceiveStream;
+
+        public async Task ConnectAsync()
+        {
+            var uri = _options.Uri;
+            if (!uri.StartsWith("ws://", StringComparison.OrdinalIgnoreCase))
+            {
+                uri = "ws://" + uri;
+            }
+
+            _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 +110,14 @@
     <DocumentationFile>bin\x64\Release\MQTTnet.XML</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="Implementations\MqttCommunicationAdapterFactory.cs" />
+    <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 +128,7 @@
   </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 +1,13 @@
-using System;
-using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Client;
-using MQTTnet.Core.Serializer;
+using MQTTnet.Core.Client;
 using MQTTnet.Implementations;
 
 namespace MQTTnet
 {
-    public class MqttClientFactory
+    public class MqttClientFactory : IMqttClientFactory
     {
-        public IMqttClient CreateMqttClient(MqttClientOptions options)
+        public IMqttClient CreateMqttClient()
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-
-            return new MqttClient(options, new MqttChannelCommunicationAdapter(new MqttTcpChannel(), new MqttPacketSerializer()));
+            return new MqttClient(new MqttCommunicationAdapterFactory());
         }
     }
 }

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("2.2.1.0")]
-[assembly: AssemblyFileVersion("2.2.1.0")]
+[assembly: AssemblyVersion("2.4.0.0")]
+[assembly: AssemblyFileVersion("2.4.0.0")]

MQTTnet.Core/Adapter/IMqttCommunicationAdapter.cs

@@ -1,6 +1,7 @@
 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;
 
@@ -8,14 +9,14 @@ namespace MQTTnet.Core.Adapter
 {
     public interface IMqttCommunicationAdapter
     {
-        Task ConnectAsync(MqttClientOptions options, TimeSpan timeout);
-
-        Task DisconnectAsync();
-
-        Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout);
-
-        Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout);
-
         IMqttPacketSerializer PacketSerializer { get; }
+
+        Task ConnectAsync(TimeSpan timeout);
+
+        Task DisconnectAsync(TimeSpan timeout);
+
+        Task SendPacketsAsync(TimeSpan timeout, CancellationToken cancellationToken, IEnumerable<MqttBasePacket> packets);
+
+        Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout, CancellationToken cancellationToken);
     }
 }

MQTTnet.Core/Adapter/IMqttServerAdapter.cs

@@ -1,14 +1,14 @@
 using System;
+using System.Threading.Tasks;
 using MQTTnet.Core.Server;
 
 namespace MQTTnet.Core.Adapter
 {
     public interface IMqttServerAdapter
     {
-        event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        event Action<IMqttCommunicationAdapter> ClientAccepted;
 
-        void Start(MqttServerOptions options);
-
-        void Stop();
+        Task StartAsync(MqttServerOptions options);
+        Task StopAsync();
     }
 }

MQTTnet.Core/Adapter/MqttChannelCommunicationAdapter.cs

@@ -1,9 +1,12 @@
 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;
 
@@ -12,6 +15,7 @@ namespace MQTTnet.Core.Adapter
     public class MqttChannelCommunicationAdapter : IMqttCommunicationAdapter
     {
         private readonly IMqttCommunicationChannel _channel;
+        private readonly SemaphoreSlim _semaphore = new SemaphoreSlim(1, 1);
 
         public MqttChannelCommunicationAdapter(IMqttCommunicationChannel channel, IMqttPacketSerializer serializer)
         {
@@ -21,72 +25,185 @@ namespace MQTTnet.Core.Adapter
 
         public IMqttPacketSerializer PacketSerializer { get; }
 
-        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
+        public async Task ConnectAsync(TimeSpan timeout)
         {
-            await ExecuteWithTimeoutAsync(_channel.ConnectAsync(options), timeout);
+            try
+            {
+                await _channel.ConnectAsync().TimeoutAfter(timeout).ConfigureAwait(false);
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
         }
 
-        public async Task DisconnectAsync()
+        public async Task DisconnectAsync(TimeSpan timeout)
         {
-            await _channel.DisconnectAsync();
+            try
+            {
+                await _channel.DisconnectAsync().TimeoutAfter(timeout).ConfigureAwait(false);
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
         }
 
-        public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
+        public async Task SendPacketsAsync(TimeSpan timeout, CancellationToken cancellationToken, IEnumerable<MqttBasePacket> packets)
         {
-            MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), $"TX >>> {packet} [Timeout={timeout}]");
+            await _semaphore.WaitAsync(cancellationToken);
 
-            await ExecuteWithTimeoutAsync(PacketSerializer.SerializeAsync(packet, _channel), timeout);
+            try
+            {
+                foreach (var packet in packets)
+                {
+                    if (packet == null)
+                    {
+                        continue;
+                    }
+
+                    MqttNetTrace.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);
+                }
+
+                if (timeout > TimeSpan.Zero)
+                {
+                    await _channel.SendStream.FlushAsync(cancellationToken).TimeoutAfter(timeout).ConfigureAwait(false);
+                }
+                else
+                {
+                    await _channel.SendStream.FlushAsync(cancellationToken).ConfigureAwait(false);
+                }
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
+            finally
+            {
+                _semaphore.Release();
+            }
         }
 
-        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
+        public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout, CancellationToken cancellationToken)
         {
-            MqttBasePacket packet;
-            if (timeout > TimeSpan.Zero)
+            try
             {
-                packet = await ExecuteWithTimeoutAsync(PacketSerializer.DeserializeAsync(_channel), timeout);
-            }
-            else
-            {
-                packet = await PacketSerializer.DeserializeAsync(_channel);
-            }
+                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 (packet == null)
-            {
-                throw new MqttProtocolViolationException("Received malformed packet.");
-            }
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    throw new TaskCanceledException();
+                }
 
-            MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), $"RX <<< {packet}");
-            return packet;
+                var packet = PacketSerializer.Deserialize(receivedMqttPacket);
+                if (packet == null)
+                {
+                    throw new MqttProtocolViolationException("Received malformed packet.");
+                }
+
+                MqttNetTrace.Information(nameof(MqttChannelCommunicationAdapter), "RX <<< {0}", packet);
+                return packet;
+            }
+            catch (TaskCanceledException)
+            {
+                throw;
+            }
+            catch (OperationCanceledException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationTimedOutException)
+            {
+                throw;
+            }
+            catch (MqttCommunicationException)
+            {
+                throw;
+            }
+            catch (Exception exception)
+            {
+                throw new MqttCommunicationException(exception);
+            }
         }
 
-        private static async Task<TResult> ExecuteWithTimeoutAsync<TResult>(Task<TResult> task, TimeSpan timeout)
+        private static async Task<ReceivedMqttPacket> ReceiveAsync(Stream stream, CancellationToken cancellationToken)
         {
-            var timeoutTask = Task.Delay(timeout);
-            if (await Task.WhenAny(timeoutTask, task) == timeoutTask)
+            var header = MqttPacketReader.ReadHeaderFromSource(stream, cancellationToken);
+
+            if (header.BodyLength == 0)
             {
-                throw new MqttCommunicationTimedOutException();
+                return new ReceivedMqttPacket(header, new MemoryStream(0));
             }
 
-            if (task.IsFaulted)
-            {
-                throw new MqttCommunicationException(task.Exception);
-            }
+            var body = new byte[header.BodyLength];
 
-            return task.Result;
-        }
-
-        private static async Task ExecuteWithTimeoutAsync(Task task, TimeSpan timeout)
-        {
-            var timeoutTask = Task.Delay(timeout);
-            if (await Task.WhenAny(timeoutTask, task) == timeoutTask)
+            var offset = 0;
+            do
             {
-                throw new MqttCommunicationTimedOutException();
-            }
+                var readBytesCount = await stream.ReadAsync(body, offset, body.Length - offset, cancellationToken).ConfigureAwait(false);
+                offset += readBytesCount;
+            } while (offset < header.BodyLength);
 
-            if (task.IsFaulted)
-            {
-                throw new MqttCommunicationException(task.Exception);
-            }
+            return new ReceivedMqttPacket(header, new MemoryStream(body, 0, body.Length));
         }
     }
-}
+}

MQTTnet.Core/Adapter/MqttClientConnectedEventArgs.cs

@@ -1,17 +1,15 @@
-using System;
+using MQTTnet.Core.Server;
+using System;
 
 namespace MQTTnet.Core.Adapter
 {
     public class MqttClientConnectedEventArgs : EventArgs
     {
-        public MqttClientConnectedEventArgs(string identifier, IMqttCommunicationAdapter clientAdapter)
+        public MqttClientConnectedEventArgs(ConnectedMqttClient client)
         {
-            Identifier = identifier ?? throw new ArgumentNullException(nameof(identifier));
-            ClientAdapter = clientAdapter ?? throw new ArgumentNullException(nameof(clientAdapter));
+            Client = client ?? throw new ArgumentNullException(nameof(client));
         }
 
-        public string Identifier { get; }
-
-        public IMqttCommunicationAdapter ClientAdapter { get; }
+        public ConnectedMqttClient Client { get; }
     }
 }

MQTTnet.Core/Adapter/MqttClientDisconnectedEventArgs.cs

@@ -0,0 +1,15 @@
+using MQTTnet.Core.Server;
+using System;
+
+namespace MQTTnet.Core.Adapter
+{
+    public class MqttClientDisconnectedEventArgs : EventArgs
+    {
+        public MqttClientDisconnectedEventArgs(ConnectedMqttClient client)
+        {
+            Client = client ?? throw new ArgumentNullException(nameof(client));
+        }
+        
+        public ConnectedMqttClient Client { get; }
+    }
+}

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 +1,15 @@
 using System.Threading.Tasks;
-using MQTTnet.Core.Client;
+using System.IO;
 
 namespace MQTTnet.Core.Channel
 {
     public interface IMqttCommunicationChannel
     {
-        Task ConnectAsync(MqttClientOptions options);
+        Stream SendStream { get; }
+        Stream ReceiveStream { get; }
+        Stream RawReceiveStream { get; }
 
+        Task ConnectAsync();
         Task DisconnectAsync();
-
-        Task WriteAsync(byte[] buffer);
-
-        Task ReadAsync(byte[] buffer);
     }
 }

MQTTnet.Core/Client/IMqttClient.cs

@@ -13,12 +13,12 @@ namespace MQTTnet.Core.Client
         event EventHandler Connected;
         event EventHandler Disconnected;
 
-        Task ConnectAsync(MqttApplicationMessage willApplicationMessage = null);
+        Task ConnectAsync(MqttClientOptions options);
         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();
+    }
+}

MQTTnet.Core/Client/IMqttCommunicationAdapterFactory.cs

@@ -0,0 +1,9 @@
+using MQTTnet.Core.Adapter;
+
+namespace MQTTnet.Core.Client
+{
+    public interface IMqttCommunicationAdapterFactory
+    {
+        IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options);
+    }
+}

MQTTnet.Core/Client/MqttClient.cs

@@ -15,174 +15,198 @@ 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 readonly IMqttCommunicationAdapterFactory _communicationChannelFactory;
 
-        private bool _disconnectedEventSuspended;
+        private MqttClientOptions _options;
+        private bool _isReceivingPackets;
         private int _latestPacketIdentifier;
         private CancellationTokenSource _cancellationTokenSource;
+        private IMqttCommunicationAdapter _adapter;
 
-        public MqttClient(MqttClientOptions options, IMqttCommunicationAdapter adapter)
+        public MqttClient(IMqttCommunicationAdapterFactory communicationChannelFactory)
         {
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-            _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
-
-            _adapter.PacketSerializer.ProtocolVersion = options.ProtocolVersion;
+            _communicationChannelFactory = communicationChannelFactory ?? throw new ArgumentNullException(nameof(communicationChannelFactory));
         }
 
         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)
+        public async Task ConnectAsync(MqttClientOptions options)
         {
-            MqttTrace.Verbose(nameof(MqttClient), "Trying to connect.");
+            if (options == null) throw new ArgumentNullException(nameof(options));
 
-            if (IsConnected)
-            {
-                throw new MqttProtocolViolationException("It is not allowed to connect with a server after the connection is established.");
-            }
+            ThrowIfConnected("It is not allowed to connect with a server after the connection is established.");
 
             try
             {
-                _disconnectedEventSuspended = false;
-
-                await _adapter.ConnectAsync(_options, _options.DefaultCommunicationTimeout);
-
-                MqttTrace.Verbose(nameof(MqttClient), "Connection with server established.");
-
-                var connectPacket = new MqttConnectPacket
-                {
-                    ClientId = _options.ClientId,
-                    Username = _options.UserName,
-                    Password = _options.Password,
-                    CleanSession = _options.CleanSession,
-                    KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
-                    WillMessage = willApplicationMessage
-                };
-
+                _options = options;
                 _cancellationTokenSource = new CancellationTokenSource();
                 _latestPacketIdentifier = 0;
                 _packetDispatcher.Reset();
 
-                StartReceivePackets();
+                _adapter = _communicationChannelFactory.CreateMqttCommunicationAdapter(options);
+                
+                MqttNetTrace.Verbose(nameof(MqttClient), "Trying to connect with server.");
+                await _adapter.ConnectAsync(_options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                MqttNetTrace.Verbose(nameof(MqttClient), "Connection with server established.");
 
-                var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket);
-                if (response.ConnectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
-                {
-                    await DisconnectInternalAsync();
-                    throw new MqttConnectingFailedException(response.ConnectReturnCode);
-                }
+                await SetupIncomingPacketProcessingAsync();
+                await AuthenticateAsync(options.WillMessage);
+
+                MqttNetTrace.Verbose(nameof(MqttClient), "MQTT connection with server established.");
 
                 if (_options.KeepAlivePeriod != TimeSpan.Zero)
                 {
-                    StartSendKeepAliveMessages();
+                    StartSendKeepAliveMessages(_cancellationTokenSource.Token);
                 }
 
-                MqttTrace.Verbose(nameof(MqttClient), "MQTT connection with server established.");
-
-                IsConnected = true;
                 Connected?.Invoke(this, EventArgs.Empty);
             }
             catch (Exception)
             {
-                await DisconnectInternalAsync();
+                await DisconnectInternalAsync().ConfigureAwait(false);
                 throw;
             }
         }
 
         public async Task DisconnectAsync()
         {
+            if (!IsConnected)
+            {
+                return;
+            }
+
             try
             {
-                await SendAsync(new MqttDisconnectPacket());
+                await SendAsync(new MqttDisconnectPacket()).ConfigureAwait(false);
             }
             finally
             {
-                await DisconnectInternalAsync();
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
         }
 
-        public Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters)
+        public async Task<IList<MqttSubscribeResult>> SubscribeAsync(IEnumerable<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
             {
                 PacketIdentifier = GetNewPacketIdentifier(),
-                TopicFilters = topicFilters
+                TopicFilters = topicFilters.ToList()
             };
 
-            var response = await SendAndReceiveAsync<MqttSubAckPacket>(subscribePacket);
+            var response = await SendAndReceiveAsync<MqttSubAckPacket>(subscribePacket).ConfigureAwait(false);
 
-            if (response.SubscribeReturnCodes.Count != topicFilters.Count)
+            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 topicFilters.Select((t, i) => new MqttSubscribeResult(t, response.SubscribeReturnCodes[i])).ToList();
+            return subscribePacket.TopicFilters.Select((t, i) => new MqttSubscribeResult(t, response.SubscribeReturnCodes[i])).ToList();
         }
 
-        public Task Unsubscribe(params string[] topicFilters)
+        public async Task UnsubscribeAsync(IEnumerable<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
+                TopicFilters = topicFilters.ToList()
             };
 
             await SendAndReceiveAsync<MqttUnsubAckPacket>(unsubscribePacket);
         }
 
-        public async Task PublishAsync(MqttApplicationMessage applicationMessage)
+        public async Task PublishAsync(IEnumerable<MqttApplicationMessage> applicationMessages)
         {
-            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
             ThrowIfNotConnected();
 
-            var publishPacket = applicationMessage.ToPublishPacket();
+            var publishPackets = applicationMessages.Select(m => m.ToPublishPacket());
 
-            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
+            foreach (var qosGroup in publishPackets.GroupBy(p => p.QualityOfServiceLevel))
             {
-                // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
-                await SendAsync(publishPacket);
+                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();
+                        }
+                }
             }
-            else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
+        }
+
+        private async Task AuthenticateAsync(MqttApplicationMessage willApplicationMessage)
+        {
+            var connectPacket = new MqttConnectPacket
             {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
+                ClientId = _options.ClientId,
+                Username = _options.UserName,
+                Password = _options.Password,
+                CleanSession = _options.CleanSession,
+                KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
+                WillMessage = willApplicationMessage
+            };
+
+            var response = await SendAndReceiveAsync<MqttConnAckPacket>(connectPacket).ConfigureAwait(false);
+            if (response.ConnectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
+            {
+                throw new MqttConnectingFailedException(response.ConnectReturnCode);
             }
-            else if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
+        }
+
+        private async Task SetupIncomingPacketProcessingAsync()
+        {
+            _isReceivingPackets = false;
+
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            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
+
+            while (!_isReceivingPackets && _cancellationTokenSource != null && !_cancellationTokenSource.IsCancellationRequested)
             {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket);
-                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>());
+                await Task.Delay(TimeSpan.FromMilliseconds(100));
             }
         }
 
@@ -191,92 +215,102 @@ 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);
+                MqttNetTrace.Information(nameof(MqttClient), "Disconnected from adapter.");
             }
             catch (Exception exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "Error while disconnecting.");
+                MqttNetTrace.Warning(nameof(MqttClient), exception, "Error while disconnecting from adapter.");
             }
             finally
             {
-                _cancellationTokenSource?.Cancel(false);
-                _cancellationTokenSource?.Dispose();
-                _cancellationTokenSource = null;
-
-                IsConnected = false;
-
-                if (!_disconnectedEventSuspended)
-                {
-                    _disconnectedEventSuspended = true;
-                    Disconnected?.Invoke(this, EventArgs.Empty);
-                }
+                Disconnected?.Invoke(this, EventArgs.Empty);
             }
         }
 
-        private Task ProcessReceivedPacketAsync(MqttBasePacket mqttPacket)
+        private async Task ProcessReceivedPacketAsync(MqttBasePacket packet)
         {
             try
             {
-                if (mqttPacket is MqttPingReqPacket)
+                MqttNetTrace.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.");
+                MqttNetTrace.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.");
+                MqttNetTrace.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)
@@ -288,50 +322,33 @@ 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)
-                {
-                    return true;
-                }
-
-                return pi1.PacketIdentifier == pi2.PacketIdentifier;
-            }
-
-            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()
@@ -341,79 +358,99 @@ namespace MQTTnet.Core.Client
 
         private async Task SendKeepAliveMessagesAsync(CancellationToken cancellationToken)
         {
-            MqttTrace.Information(nameof(MqttClient), "Start sending keep alive packets.");
+            MqttNetTrace.Information(nameof(MqttClient), "Start sending keep alive packets.");
 
             try
             {
                 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 (OperationCanceledException)
+            {
+            }
             catch (MqttCommunicationException exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication error while receiving packets.");
-                await DisconnectInternalAsync();
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                MqttNetTrace.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.");
-                await DisconnectInternalAsync();
+                MqttNetTrace.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.");
+                MqttNetTrace.Information(nameof(MqttClient), "Stopped sending keep alive packets.");
             }
         }
 
         private async Task ReceivePackets(CancellationToken cancellationToken)
         {
-            MqttTrace.Information(nameof(MqttClient), "Start receiving packets.");
+            MqttNetTrace.Information(nameof(MqttClient), "Start receiving packets.");
+
             try
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
-                    var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero);
-                    MqttTrace.Information(nameof(MqttClient), $"Received <<< {packet}");
+                    _isReceivingPackets = true;
+
+                    var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
+                    if (cancellationToken.IsCancellationRequested)
+                    {
+                        return;
+                    }
 
                     StartProcessReceivedPacket(packet, cancellationToken);
                 }
             }
+            catch (OperationCanceledException)
+            {
+            }
             catch (MqttCommunicationException exception)
             {
-                MqttTrace.Warning(nameof(MqttClient), exception, "MQTT communication exception while receiving packets.");
-                await DisconnectInternalAsync();
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                MqttNetTrace.Warning(nameof(MqttClient), exception, "MQTT communication exception while receiving packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClient), exception, "Unhandled exception while receiving packets.");
-                await DisconnectInternalAsync();
+                MqttNetTrace.Error(nameof(MqttClient), exception, "Unhandled exception while receiving packets.");
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             finally
             {
-                MqttTrace.Information(nameof(MqttClient), "Stopped receiving packets.");
+                MqttNetTrace.Information(nameof(MqttClient), "Stopped receiving packets.");
             }
         }
 
         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);
+            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 StartReceivePackets()
+        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.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
-        }
-
-        private void StartSendKeepAliveMessages()
-        {
-#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(() => 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

@@ -3,14 +3,12 @@ using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Client
 {
-    public sealed class MqttClientOptions
+    public abstract class MqttClientOptions
     {
-        public string Server { get; set; }
-
-        public int? Port { get; set; }
-
         public MqttClientTlsOptions TlsOptions { get; set; } = new MqttClientTlsOptions();
 
+        public MqttApplicationMessage WillMessage { get; set; }
+
         public string UserName { get; set; }
 
         public string Password { get; set; }

MQTTnet.Core/Client/MqttClientTcpOptions.cs

@@ -0,0 +1,9 @@
+namespace MQTTnet.Core.Client
+{
+    public class MqttClientTcpOptions : MqttClientOptions
+    {
+        public string Server { get; set; }
+
+        public int? Port { get; set; }
+    }
+}

MQTTnet.Core/Client/MqttClientTcpOptionsExtensions.cs

@@ -2,9 +2,9 @@
 
 namespace MQTTnet.Core.Client
 {
-    public static class MqttClientOptionsExtensions
+    public static class MqttClientTcpOptionsExtensions
     {
-        public static int GetPort(this MqttClientOptions options)
+        public static int GetPort(this MqttClientTcpOptions options)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
 

MQTTnet.Core/Client/MqttClientTlsOptions.cs

@@ -6,7 +6,11 @@ namespace MQTTnet.Core.Client
     {
         public bool UseTls { get; set; }
 
-        public bool CheckCertificateRevocation { get; set; }
+        public bool IgnoreCertificateRevocationErrors { get; set; }
+
+        public bool IgnoreCertificateChainErrors { get; set; }
+
+        public bool AllowUntrustedCertificates { get; set; }
 
         public List<byte[]> Certificates { get; set; }
     }

MQTTnet.Core/Client/MqttClientWebSocketOptions.cs

@@ -0,0 +1,7 @@
+namespace MQTTnet.Core.Client
+{
+    public class MqttClientWebSocketOptions : MqttClientOptions
+    {
+        public string Uri { get; set; }
+    }
+}

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)
+            {
+                MqttNetTrace.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/MqttNetTrace.cs

@@ -0,0 +1,63 @@
+using System;
+
+namespace MQTTnet.Core.Diagnostics
+{
+    public static class MqttNetTrace
+    {
+        public static event EventHandler<MqttNetTraceMessagePublishedEventArgs> TraceMessagePublished;
+
+        public static void Verbose(string source, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Verbose, null, message, parameters);
+        }
+
+        public static void Information(string source, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Information, null, message, parameters);
+        }
+
+        public static void Warning(string source, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Warning, null, message, parameters);
+        }
+
+        public static void Warning(string source, Exception exception, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Warning, exception, message, parameters);
+        }
+
+        public static void Error(string source, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Error, null, message, parameters);
+        }
+
+        public static void Error(string source, Exception exception, string message, params object[] parameters)
+        {
+            Publish(source, MqttNetTraceLevel.Error, exception, message, parameters);
+        }
+
+        private static void Publish(string source, MqttNetTraceLevel traceLevel, Exception exception, string message, params object[] parameters)
+        {
+            var handler = TraceMessagePublished;
+            if (handler == null)
+            {
+                return;
+            }
+
+            if (parameters?.Length > 0)
+            {
+                try
+                {
+                    message = string.Format(message, parameters);
+                }
+                catch (Exception formatException)
+                {
+                    Error(nameof(MqttNetTrace), formatException, "Error while tracing message: " + message);
+                    return;
+                }
+            }
+
+            handler.Invoke(null, new MqttNetTraceMessagePublishedEventArgs(Environment.CurrentManagedThreadId, source, traceLevel, message, exception));
+        }
+    }
+}

MQTTnet.Core/Diagnostics/MqttNetTraceLevel.cs

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

MQTTnet.Core/Diagnostics/MqttNetTraceMessagePublishedEventArgs.cs

@@ -2,9 +2,9 @@
 
 namespace MQTTnet.Core.Diagnostics
 {
-    public sealed class MqttTraceMessagePublishedEventArgs : EventArgs
+    public sealed class MqttNetTraceMessagePublishedEventArgs : EventArgs
     {
-        public MqttTraceMessagePublishedEventArgs(int threadId, string source, MqttTraceLevel level, string message, Exception exception)
+        public MqttNetTraceMessagePublishedEventArgs(int threadId, string source, MqttNetTraceLevel level, string message, Exception exception)
         {
             ThreadId = threadId;
             Source = source;
@@ -17,7 +17,7 @@ namespace MQTTnet.Core.Diagnostics
 
         public string Source { get; }
 
-        public MqttTraceLevel Level { get; }
+        public MqttNetTraceLevel Level { get; }
 
         public string Message { get; }
 

MQTTnet.Core/Diagnostics/MqttTrace.cs

@@ -1,44 +0,0 @@
-using System;
-
-namespace MQTTnet.Core.Diagnostics
-{
-    public static class MqttTrace
-    {
-        public static event EventHandler<MqttTraceMessagePublishedEventArgs> TraceMessagePublished;
-
-        public static void Verbose(string source, string message)
-        {
-            Publish(source, MqttTraceLevel.Verbose, null, message);
-        }
-
-        public static void Information(string source, string message)
-        {
-            Publish(source, MqttTraceLevel.Information, null, message);
-        }
-
-        public static void Warning(string source, string message)
-        {
-            Publish(source, MqttTraceLevel.Warning, null, message);
-        }
-
-        public static void Warning(string source, Exception exception, string message)
-        {
-            Publish(source, MqttTraceLevel.Warning, exception, message);
-        }
-
-        public static void Error(string source, string message)
-        {
-            Publish(source, MqttTraceLevel.Error, null, message);
-        }
-
-        public static void Error(string source, Exception exception, string message)
-        {
-            Publish(source, MqttTraceLevel.Error, exception, message);
-        }
-
-        private static void Publish(string source, MqttTraceLevel traceLevel, Exception exception, string message)
-        {
-            TraceMessagePublished?.Invoke(null, new MqttTraceMessagePublishedEventArgs(Environment.CurrentManagedThreadId, source, traceLevel, message, exception));
-        }
-    }
-}

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>2.2.1.0</FileVersion>
-    <AssemblyVersion>2.2.1.0</AssemblyVersion>
+    <FileVersion>2.4.0.0</FileVersion>
+    <AssemblyVersion>2.4.0.0</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

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Packets
 {
-    public sealed class MqttConnectPacket: MqttBasePacket
+    public sealed class MqttConnectPacket : MqttBasePacket
     {
         public MqttProtocolVersion ProtocolVersion { get; set; }
 
@@ -20,7 +20,7 @@ namespace MQTTnet.Core.Packets
 
         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}]";
+            var topicFiltersText = string.Join(",", TopicFilters.Select(f => f.Topic + "@" + f.QualityOfServiceLevel));
+            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

@@ -1,5 +1,4 @@
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Serializer
@@ -8,8 +7,8 @@ namespace MQTTnet.Core.Serializer
     {
         MqttProtocolVersion ProtocolVersion { get; set; }
 
-        Task SerializeAsync(MqttBasePacket mqttPacket, IMqttCommunicationChannel destination);
+        byte[] Serialize(MqttBasePacket mqttPacket);
 
-        Task<MqttBasePacket> DeserializeAsync(IMqttCommunicationChannel source);
+        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(1024);
-        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

@@ -1,8 +1,9 @@
 using System;
+using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
+using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
@@ -16,232 +17,251 @@ namespace MQTTnet.Core.Serializer
 
         public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
 
-        public Task SerializeAsync(MqttBasePacket packet, IMqttCommunicationChannel destination)
+        public byte[] Serialize(MqttBasePacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
-            if (destination == null) throw new ArgumentNullException(nameof(destination));
 
+            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 SerializeAsync(connectPacket, destination);
+                return Serialize(connectPacket, writer);
             }
 
             if (packet is MqttConnAckPacket connAckPacket)
             {
-                return SerializeAsync(connAckPacket, destination);
+                return Serialize(connAckPacket, writer);
             }
 
             if (packet is MqttDisconnectPacket disconnectPacket)
             {
-                return SerializeAsync(disconnectPacket, destination);
+                return Serialize(disconnectPacket, writer);
             }
 
             if (packet is MqttPingReqPacket pingReqPacket)
             {
-                return SerializeAsync(pingReqPacket, destination);
+                return Serialize(pingReqPacket, writer);
             }
 
             if (packet is MqttPingRespPacket pingRespPacket)
             {
-                return SerializeAsync(pingRespPacket, destination);
+                return Serialize(pingRespPacket, writer);
             }
 
             if (packet is MqttPublishPacket publishPacket)
             {
-                return SerializeAsync(publishPacket, destination);
+                return Serialize(publishPacket, writer);
             }
 
             if (packet is MqttPubAckPacket pubAckPacket)
             {
-                return SerializeAsync(pubAckPacket, destination);
+                return Serialize(pubAckPacket, writer);
             }
 
             if (packet is MqttPubRecPacket pubRecPacket)
             {
-                return SerializeAsync(pubRecPacket, destination);
+                return Serialize(pubRecPacket, writer);
             }
 
             if (packet is MqttPubRelPacket pubRelPacket)
             {
-                return SerializeAsync(pubRelPacket, destination);
+                return Serialize(pubRelPacket, writer);
             }
 
             if (packet is MqttPubCompPacket pubCompPacket)
             {
-                return SerializeAsync(pubCompPacket, destination);
+                return Serialize(pubCompPacket, writer);
             }
 
             if (packet is MqttSubscribePacket subscribePacket)
             {
-                return SerializeAsync(subscribePacket, destination);
+                return Serialize(subscribePacket, writer);
             }
 
             if (packet is MqttSubAckPacket subAckPacket)
             {
-                return SerializeAsync(subAckPacket, destination);
+                return Serialize(subAckPacket, writer);
             }
 
             if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                return SerializeAsync(unsubscribePacket, destination);
+                return Serialize(unsubscribePacket, writer);
             }
 
             if (packet is MqttUnsubAckPacket unsubAckPacket)
             {
-                return SerializeAsync(unsubAckPacket, destination);
+                return Serialize(unsubAckPacket, writer);
             }
 
             throw new MqttProtocolViolationException("Packet type invalid.");
         }
 
-        public async Task<MqttBasePacket> DeserializeAsync(IMqttCommunicationChannel source)
+        public MqttBasePacket Deserialize(ReceivedMqttPacket receivedMqttPacket)
         {
-            if (source == null) throw new ArgumentNullException(nameof(source));
+            if (receivedMqttPacket == null) throw new ArgumentNullException(nameof(receivedMqttPacket));
 
-            using (var mqttPacketReader = new MqttPacketReader(source))
+            using (var reader = new MqttPacketReader(receivedMqttPacket))
             {
-                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.");
-                        }
-                }
+                return Deserialize(receivedMqttPacket.Header, reader);
             }
         }
 
-        private static async Task<MqttBasePacket> DeserializeUnsubscribeAsync(MqttPacketReader 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 = await reader.ReadRemainingDataUShortAsync(),
+                PacketIdentifier = reader.ReadUInt16(),
             };
 
             while (!reader.EndOfRemainingData)
             {
-                packet.TopicFilters.Add(await reader.ReadRemainingDataStringWithLengthPrefixAsync());
+                packet.TopicFilters.Add(reader.ReadStringWithLengthPrefix());
             }
 
             return packet;
         }
 
-        private static async Task<MqttBasePacket> DeserializeSubscribeAsync(MqttPacketReader reader)
+        private static MqttBasePacket DeserializeSubscribe(MqttPacketReader reader)
         {
             var packet = new MqttSubscribePacket
             {
-                PacketIdentifier = await reader.ReadRemainingDataUShortAsync(),
+                PacketIdentifier = reader.ReadUInt16()
             };
 
             while (!reader.EndOfRemainingData)
             {
                 packet.TopicFilters.Add(new TopicFilter(
-                    await reader.ReadRemainingDataStringWithLengthPrefixAsync(),
-                    (MqttQualityOfServiceLevel)await reader.ReadRemainingDataByteAsync()));
+                    reader.ReadStringWithLengthPrefix(),
+                    (MqttQualityOfServiceLevel)reader.ReadByte()));
             }
 
             return packet;
         }
 
-        private static async Task<MqttBasePacket> DeserializePublishAsync(MqttPacketReader reader)
+        private static MqttBasePacket DeserializePublish(MqttPacketReader reader, MqttPacketHeader mqttPacketHeader)
         {
-            var fixedHeader = new ByteReader(reader.FixedHeader);
+            var fixedHeader = new ByteReader(mqttPacketHeader.FixedHeader);
             var retain = fixedHeader.Read();
             var qualityOfServiceLevel = (MqttQualityOfServiceLevel)fixedHeader.Read(2);
             var dup = fixedHeader.Read();
 
-            var topic = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
+            var topic = reader.ReadStringWithLengthPrefix();
 
             ushort packetIdentifier = 0;
             if (qualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
             {
-                packetIdentifier = await reader.ReadRemainingDataUShortAsync();
+                packetIdentifier = reader.ReadUInt16();
             }
 
             var packet = new MqttPublishPacket
@@ -250,22 +270,22 @@ namespace MQTTnet.Core.Serializer
                 QualityOfServiceLevel = qualityOfServiceLevel,
                 Dup = dup,
                 Topic = topic,
-                Payload = await reader.ReadRemainingDataAsync(),
+                Payload = reader.ReadRemainingData(),
                 PacketIdentifier = packetIdentifier
             };
 
             return packet;
         }
 
-        private static async Task<MqttBasePacket> DeserializeConnectAsync(MqttPacketReader reader)
+        private static MqttBasePacket DeserializeConnect(MqttPacketReader reader)
         {
-            await reader.ReadRemainingDataAsync(2); // Skip 2 bytes
+            reader.ReadBytes(2); // Skip 2 bytes
 
             MqttProtocolVersion protocolVersion;
-            var protocolName = await reader.ReadRemainingDataAsync(4);
+            var protocolName = reader.ReadBytes(4);
             if (protocolName.SequenceEqual(ProtocolVersionV310Name))
             {
-                await reader.ReadRemainingDataAsync(2);
+                reader.ReadBytes(2);
                 protocolVersion = MqttProtocolVersion.V310;
             }
             else if (protocolName.SequenceEqual(ProtocolVersionV311Name))
@@ -277,8 +297,8 @@ namespace MQTTnet.Core.Serializer
                 throw new MqttProtocolViolationException("Protocol name is not supported.");
             }
 
-            var protocolLevel = await reader.ReadRemainingDataByteAsync();
-            var connectFlags = await reader.ReadRemainingDataByteAsync();
+            var protocolLevel = reader.ReadByte();
+            var connectFlags = reader.ReadByte();
 
             var connectFlagsReader = new ByteReader(connectFlags);
             connectFlagsReader.Read(); // Reserved.
@@ -295,51 +315,51 @@ namespace MQTTnet.Core.Serializer
             var passwordFlag = connectFlagsReader.Read();
             var usernameFlag = connectFlagsReader.Read();
 
-            packet.KeepAlivePeriod = await reader.ReadRemainingDataUShortAsync();
-            packet.ClientId = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
+            packet.KeepAlivePeriod = reader.ReadUInt16();
+            packet.ClientId = reader.ReadStringWithLengthPrefix();
 
             if (willFlag)
             {
                 packet.WillMessage = new MqttApplicationMessage(
-                    await reader.ReadRemainingDataStringWithLengthPrefixAsync(),
-                    await reader.ReadRemainingDataWithLengthPrefixAsync(),
+                    reader.ReadStringWithLengthPrefix(),
+                    reader.ReadWithLengthPrefix(),
                     (MqttQualityOfServiceLevel)willQoS,
                     willRetain);
             }
 
             if (usernameFlag)
             {
-                packet.Username = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
+                packet.Username = reader.ReadStringWithLengthPrefix();
             }
 
             if (passwordFlag)
             {
-                packet.Password = await reader.ReadRemainingDataStringWithLengthPrefixAsync();
+                packet.Password = reader.ReadStringWithLengthPrefix();
             }
 
             ValidateConnectPacket(packet);
             return packet;
         }
 
-        private static async Task<MqttBasePacket> DeserializeSubAck(MqttPacketReader reader)
+        private static MqttBasePacket DeserializeSubAck(MqttPacketReader reader)
         {
             var packet = new MqttSubAckPacket
             {
-                PacketIdentifier = await reader.ReadRemainingDataUShortAsync()
+                PacketIdentifier = reader.ReadUInt16()
             };
 
             while (!reader.EndOfRemainingData)
             {
-                packet.SubscribeReturnCodes.Add((MqttSubscribeReturnCode)await reader.ReadRemainingDataByteAsync());
+                packet.SubscribeReturnCodes.Add((MqttSubscribeReturnCode)reader.ReadByte());
             }
 
             return packet;
         }
 
-        private static async Task<MqttBasePacket> DeserializeConnAck(MqttPacketReader reader)
+        private static MqttBasePacket DeserializeConnAck(MqttPacketReader reader)
         {
-            var variableHeader1 = await reader.ReadRemainingDataByteAsync();
-            var variableHeader2 = await reader.ReadRemainingDataByteAsync();
+            var variableHeader1 = reader.ReadByte();
+            var variableHeader2 = reader.ReadByte();
 
             var packet = new MqttConnAckPacket
             {
@@ -366,260 +386,223 @@ namespace MQTTnet.Core.Serializer
             }
         }
 
-        private Task SerializeAsync(MqttConnectPacket packet, IMqttCommunicationChannel destination)
+        private byte Serialize(MqttConnectPacket packet, MqttPacketWriter writer)
         {
             ValidateConnectPacket(packet);
 
-            using (var output = new MqttPacketWriter())
+            // Write variable header
+            writer.Write(0x00, 0x04); // 3.1.2.1 Protocol Name
+            if (ProtocolVersion == MqttProtocolVersion.V311)
             {
-                // Write variable header
-                output.Write(0x00, 0x04); // 3.1.2.1 Protocol Name
-                if (ProtocolVersion == MqttProtocolVersion.V311)
-                {
-                    output.Write(ProtocolVersionV311Name);
-                    output.Write(0x04); // 3.1.2.2 Protocol Level (4)
-                }
-                else
-                {
-                    output.Write(ProtocolVersionV310Name);
-                    output.Write(0x64);
-                    output.Write(0x70);
-                    output.Write(0x03); // Protocol Level (3)
-                }
-                
-                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);
+                writer.Write(ProtocolVersionV311Name);
+                writer.Write(0x04); // 3.1.2.2 Protocol Level (4)
             }
-        }
-
-        private Task SerializeAsync(MqttConnAckPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
+            else
             {
-                var connectAcknowledgeFlags = new ByteWriter();
-
-                if (ProtocolVersion == MqttProtocolVersion.V311)
-                {
-                    connectAcknowledgeFlags.Write(packet.IsSessionPresent);
-                }
-                
-                output.Write(connectAcknowledgeFlags);
-                output.Write((byte)packet.ConnectReturnCode);
-
-                output.InjectFixedHeader(MqttControlPacketType.ConnAck);
-                return output.WriteToAsync(destination);
+                writer.Write(ProtocolVersionV310Name);
+                writer.Write(0x64, 0x70, 0x03); // Protocol Level (0x03)
             }
-        }
 
-        private static async Task SerializeAsync(MqttPubRelPacket packet, IMqttCommunicationChannel destination)
-        {
-            using (var output = new MqttPacketWriter())
+            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)
             {
-                output.Write(packet.PacketIdentifier);
-
-                output.InjectFixedHeader(MqttControlPacketType.PubRel, 0x02);
-                await output.WriteToAsync(destination);
+                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 static Task SerializeAsync(MqttDisconnectPacket packet, IMqttCommunicationChannel destination)
+        private byte Serialize(MqttConnAckPacket packet, MqttPacketWriter writer)
         {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, destination);
+            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 Task SerializeAsync(MqttPingReqPacket packet, IMqttCommunicationChannel destination)
+        private static byte Serialize(MqttPubRelPacket packet, MqttPacketWriter writer)
         {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.PingReq, destination);
+            writer.Write(packet.PacketIdentifier);
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.PubRel, 0x02);
         }
 
-        private static Task SerializeAsync(MqttPingRespPacket packet, IMqttCommunicationChannel destination)
+        private static byte Serialize(MqttDisconnectPacket packet, MqttPacketWriter writer)
         {
-            return SerializeEmptyPacketAsync(MqttControlPacketType.PingResp, destination);
+            return SerializeEmptyPacketAsync(MqttControlPacketType.Disconnect, writer);
         }
 
-        private static Task SerializeAsync(MqttPublishPacket packet, IMqttCommunicationChannel destination)
+        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);
 
-            using (var output = new MqttPacketWriter())
-            {
-                output.WriteWithLengthPrefix(packet.Topic);
+            writer.WriteWithLengthPrefix(packet.Topic);
 
-                if (packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+            if (packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+            {
+                writer.Write(packet.PacketIdentifier);
+            }
+            else
+            {
+                if (packet.PacketIdentifier > 0)
                 {
-                    output.Write(packet.PacketIdentifier);
+                    throw new MqttProtocolViolationException("Packet identifier must be empty if QoS == 0 [MQTT-2.3.1-5].");
                 }
-                else
+            }
+
+            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)
                 {
-                    if (packet.PacketIdentifier > 0)
-                    {
-                        throw new MqttProtocolViolationException("Packet identifier must be empty if QoS == 0 [MQTT-2.3.1-5].");
-                    }
+                    writer.WriteWithLengthPrefix(topicFilter.Topic);
+                    writer.Write((byte)topicFilter.QualityOfServiceLevel);
                 }
+            }
 
-                if (packet.Payload?.Length > 0)
+            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)
                 {
-                    output.Write(packet.Payload);
+                    writer.Write((byte)packetSubscribeReturnCode);
                 }
-
-                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);
             }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.SubAck);
         }
 
-        private static Task SerializeAsync(MqttPubAckPacket packet, IMqttCommunicationChannel destination)
+        private static byte Serialize(MqttUnsubscribePacket packet, MqttPacketWriter writer)
         {
-            using (var output = new MqttPacketWriter())
+            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)
             {
-                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 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)
                 {
-                    foreach (var topicFilter in packet.TopicFilters)
-                    {
-                        output.WriteWithLengthPrefix(topicFilter.Topic);
-                        output.Write((byte)topicFilter.QualityOfServiceLevel);
-                    }
+                    writer.WriteWithLengthPrefix(topicFilter);
                 }
-
-                output.InjectFixedHeader(MqttControlPacketType.Subscribe, 0x02);
-                return output.WriteToAsync(destination);
             }
+
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Unsubscibe, 0x02);
         }
 
-        private static Task SerializeAsync(MqttSubAckPacket packet, IMqttCommunicationChannel destination)
+        private static byte Serialize(MqttUnsubAckPacket packet, MqttPacketWriter writer)
         {
-            using (var output = new MqttPacketWriter())
-            {
-                output.Write(packet.PacketIdentifier);
+            writer.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);
-            }
+            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.UnsubAck);
         }
 
-        private static Task SerializeAsync(MqttUnsubscribePacket packet, IMqttCommunicationChannel destination)
+        private static byte SerializeEmptyPacketAsync(MqttControlPacketType type, MqttPacketWriter writer)
         {
-            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);
-            }
+            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(1024);
+        public MqttPacketWriter(Stream stream)
+            : base(stream)
+        {
+        }
 
-        public void InjectFixedHeader(MqttControlPacketType packetType, byte flags = 0)
+        public static byte BuildFixedHeader(MqttControlPacketType packetType, byte flags = 0)
         {
             var fixedHeader = (int)packetType << 4;
             fixedHeader |= flags;
-            InjectFixedHeader((byte)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/Server/IMqttServer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 
 namespace MQTTnet.Core.Server
@@ -8,11 +9,12 @@ namespace MQTTnet.Core.Server
     {
         event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
         event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        event EventHandler<MqttClientDisconnectedEventArgs> ClientDisconnected;
 
-        IList<ConnectedMqttClient> GetConnectedClients();
-        void InjectClient(string identifier, IMqttCommunicationAdapter adapter);
+        IReadOnlyList<ConnectedMqttClient> GetConnectedClients();
         void Publish(MqttApplicationMessage applicationMessage);
-        void Start();
-        void Stop();
+
+        Task StartAsync();
+        Task StopAsync();
     }
 }

MQTTnet.Core/Server/IMqttServerFactory.cs

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

MQTTnet.Core/Server/IMqttServerStorage.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace MQTTnet.Core.Server
+{
+    public interface IMqttServerStorage
+    {
+        Task SaveRetainedMessagesAsync(IList<MqttApplicationMessage> messages);
+
+        Task<IList<MqttApplicationMessage>> LoadRetainedMessagesAsync();
+    }
+}

MQTTnet.Core/Server/MqttClientMessageQueue.cs

@@ -1,134 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-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;
-
-namespace MQTTnet.Core.Server
-{
-    public sealed class MqttClientMessageQueue
-    {
-        private readonly List<MqttClientPublishPacketContext> _pendingPublishPackets = new List<MqttClientPublishPacketContext>();
-        private readonly AsyncGate _gate = new AsyncGate();
-
-        private readonly MqttServerOptions _options;
-        private CancellationTokenSource _cancellationTokenSource;
-        private IMqttCommunicationAdapter _adapter;
-
-        public MqttClientMessageQueue(MqttServerOptions options)
-        {
-            _options = options ?? throw new ArgumentNullException(nameof(options));
-        }
-
-        public void Start(IMqttCommunicationAdapter adapter)
-        {
-            if (_cancellationTokenSource != null)
-            {
-                throw new InvalidOperationException($"{nameof(MqttClientMessageQueue)} already started.");
-            }
-
-            _adapter = adapter ?? throw new ArgumentNullException(nameof(adapter));
-            _cancellationTokenSource = new CancellationTokenSource();
-
-            Task.Run(() => SendPendingPublishPacketsAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
-        }
-
-        public void Stop()
-        {
-            _adapter = null;
-            _cancellationTokenSource?.Cancel();
-            _cancellationTokenSource = null;
-        }
-
-        public void Enqueue(MqttPublishPacket publishPacket)
-        {
-            if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
-
-            lock (_pendingPublishPackets)
-            {
-                _pendingPublishPackets.Add(new MqttClientPublishPacketContext(publishPacket));
-                _gate.Set();
-            }
-        }
-
-        private async Task SendPendingPublishPacketsAsync(CancellationToken cancellationToken)
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                try
-                {
-                    await _gate.WaitOneAsync();
-                    if (cancellationToken.IsCancellationRequested)
-                    {
-                        return;
-                    }
-
-                    if (_adapter == null)
-                    {
-                        continue;
-                    }
-
-                    List<MqttClientPublishPacketContext> pendingPublishPackets;
-                    lock (_pendingPublishPackets)
-                    {
-                        pendingPublishPackets = _pendingPublishPackets.ToList();
-                    }
-
-                    foreach (var publishPacket in pendingPublishPackets)
-                    {
-                        await TrySendPendingPublishPacketAsync(publishPacket);
-                    }
-                }
-                catch (Exception e)
-                {
-                    MqttTrace.Error(nameof(MqttClientMessageQueue), e, "Error while sending pending publish packets.");
-                }
-                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/MqttClientPendingMessagesQueue.cs

@@ -0,0 +1,93 @@
+using System;
+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.Packets;
+using MQTTnet.Core.Protocol;
+
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttClientPendingMessagesQueue
+    {
+        private readonly BlockingCollection<MqttPublishPacket> _pendingPublishPackets = new BlockingCollection<MqttPublishPacket>();
+        private readonly MqttClientSession _session;
+        private readonly MqttServerOptions _options;
+
+        public MqttClientPendingMessagesQueue(MqttServerOptions options, MqttClientSession session)
+        {
+            _session = session ?? throw new ArgumentNullException(nameof(session));
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public void Start(IMqttCommunicationAdapter adapter, CancellationToken cancellationToken)
+        {
+            if (adapter == null) throw new ArgumentNullException(nameof(adapter));
+
+            Task.Run(() => SendPendingPublishPacketsAsync(adapter, cancellationToken), cancellationToken);
+        }
+
+        public void Enqueue(MqttPublishPacket publishPacket)
+        {
+            if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
+
+            _pendingPublishPackets.Add(publishPacket);
+        }
+
+        private async Task SendPendingPublishPacketsAsync(IMqttCommunicationAdapter adapter, CancellationToken cancellationToken)
+        {
+            try
+            {
+                while (!cancellationToken.IsCancellationRequested)
+                {
+                    await SendPendingPublishPacketAsync(adapter, cancellationToken);
+                }
+            }
+            catch (OperationCanceledException)
+            {
+            }
+            catch (Exception exception)
+            {
+                MqttNetTrace.Error(nameof(MqttClientPendingMessagesQueue), exception, "Unhandled exception while sending pending publish packets.");
+            }
+        }
+
+        private async Task SendPendingPublishPacketAsync(IMqttCommunicationAdapter adapter, CancellationToken cancellationToken)
+        {
+            var packet = _pendingPublishPackets.Take(cancellationToken);
+
+            try
+            {
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, packet).ConfigureAwait(false);
+            }
+            catch (Exception exception)
+            {
+                if (exception is MqttCommunicationTimedOutException)
+                {
+                    MqttNetTrace.Warning(nameof(MqttClientPendingMessagesQueue), exception, "Sending publish packet failed due to timeout.");
+                }
+                else if (exception is MqttCommunicationException)
+                {
+                    MqttNetTrace.Warning(nameof(MqttClientPendingMessagesQueue), exception, "Sending publish packet failed due to communication exception.");
+                }
+                if (exception is OperationCanceledException)
+                {
+                }
+                else
+                {
+                    MqttNetTrace.Error(nameof(MqttClientPendingMessagesQueue), exception, "Sending publish packet failed.");
+                }
+
+                if (packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+                {
+                    packet.Dup = true;
+                    _pendingPublishPackets.Add(packet, cancellationToken);
+                }
+
+                _session.Stop();
+            }
+        }
+    }
+}

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/MqttClientRetainedMessagesManager.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using MQTTnet.Core.Diagnostics;
+using MQTTnet.Core.Internal;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Server
+{
+    public sealed class MqttClientRetainedMessagesManager
+    {
+        private readonly Dictionary<string, MqttPublishPacket> _retainedMessages = new Dictionary<string, MqttPublishPacket>();
+        private readonly MqttServerOptions _options;
+
+        public MqttClientRetainedMessagesManager(MqttServerOptions options)
+        {
+            _options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        public async Task LoadMessagesAsync()
+        {
+            if (_options.Storage == null)
+            {
+                return;
+            }
+
+            try
+            {
+                var retainedMessages = await _options.Storage.LoadRetainedMessagesAsync();
+                lock (_retainedMessages)
+                {
+                    _retainedMessages.Clear();
+                    foreach (var retainedMessage in retainedMessages)
+                    {
+                        _retainedMessages[retainedMessage.Topic] = retainedMessage.ToPublishPacket();
+                    }
+                }
+            }
+            catch (Exception exception)
+            {
+                MqttNetTrace.Error(nameof(MqttClientRetainedMessagesManager), exception, "Unhandled exception while loading retained messages.");
+            }
+        }
+
+        public async Task HandleMessageAsync(string clientId, MqttPublishPacket publishPacket)
+        {
+            if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
+
+            List<MqttPublishPacket> allRetainedMessages;
+            lock (_retainedMessages)
+            {
+                if (publishPacket.Payload?.Any() == false)
+                {
+                    _retainedMessages.Remove(publishPacket.Topic);
+                    MqttNetTrace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' cleared retained message for topic '{1}'.", clientId, publishPacket.Topic);
+                }
+                else
+                {
+                    _retainedMessages[publishPacket.Topic] = publishPacket;
+                    MqttNetTrace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' updated retained message for topic '{1}'.", clientId, publishPacket.Topic);
+                }
+
+                allRetainedMessages = new List<MqttPublishPacket>(_retainedMessages.Values);
+            }
+
+            try
+            {
+                // ReSharper disable once UseNullPropagation
+                if (_options.Storage != null)
+                {
+                    await _options.Storage.SaveRetainedMessagesAsync(allRetainedMessages.Select(p => p.ToApplicationMessage()).ToList());
+                }
+            }
+            catch (Exception exception)
+            {
+                MqttNetTrace.Error(nameof(MqttClientRetainedMessagesManager), exception, "Unhandled exception while saving retained messages.");
+            }
+        }
+
+        public List<MqttPublishPacket> GetMessages(MqttSubscribePacket subscribePacket)
+        {
+            var retainedMessages = new List<MqttPublishPacket>();
+            lock (_retainedMessages)
+            {
+                foreach (var retainedMessage in _retainedMessages.Values)
+                {
+                    foreach (var topicFilter in subscribePacket.TopicFilters)
+                    {
+                        if (retainedMessage.QualityOfServiceLevel < topicFilter.QualityOfServiceLevel)
+                        {
+                            continue;
+                        }
+
+                        if (!MqttTopicFilterComparer.IsMatch(retainedMessage.Topic, topicFilter.Topic))
+                        {
+                            continue;
+                        }
+
+                        retainedMessages.Add(retainedMessage);
+                        break;
+                    }
+                }
+            }
+
+            return retainedMessages;
+        }
+    }
+}

MQTTnet.Core/Server/MqttClientSession.cs

@@ -8,76 +8,78 @@ using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Server
 {
     public sealed class MqttClientSession : IDisposable
     {
         private readonly HashSet<ushort> _unacknowledgedPublishPackets = new HashSet<ushort>();
-
+        
         private readonly MqttClientSubscriptionsManager _subscriptionsManager = new MqttClientSubscriptionsManager();
-        private readonly MqttClientMessageQueue _messageQueue;
-        private readonly Action<MqttClientSession, MqttPublishPacket> _publishPacketReceivedCallback;
+        private readonly MqttClientSessionsManager _mqttClientSessionsManager;
+        private readonly MqttClientPendingMessagesQueue _pendingMessagesQueue;
         private readonly MqttServerOptions _options;
 
+        private IMqttCommunicationAdapter _adapter;
         private CancellationTokenSource _cancellationTokenSource;
-        private string _identifier;
-        private MqttApplicationMessage _willApplicationMessage;
+        private MqttApplicationMessage _willMessage;
 
-        public MqttClientSession(string clientId, MqttServerOptions options, Action<MqttClientSession, MqttPublishPacket> publishPacketReceivedCallback)
+        public MqttClientSession(string clientId, MqttServerOptions options, MqttClientSessionsManager mqttClientSessionsManager)
         {
             ClientId = clientId;
             _options = options ?? throw new ArgumentNullException(nameof(options));
-            _publishPacketReceivedCallback = publishPacketReceivedCallback ?? throw new ArgumentNullException(nameof(publishPacketReceivedCallback));
-
-            _messageQueue = new MqttClientMessageQueue(options);
+            _mqttClientSessionsManager = mqttClientSessionsManager ?? throw new ArgumentNullException(nameof(mqttClientSessionsManager));
+            _pendingMessagesQueue = new MqttClientPendingMessagesQueue(options, this);
         }
 
         public string ClientId { get; }
 
-        public bool IsConnected => Adapter != null;
+        public MqttProtocolVersion? ProtocolVersion => _adapter?.PacketSerializer.ProtocolVersion;
 
-        public IMqttCommunicationAdapter Adapter { get; private set; }
+        public bool IsConnected => _adapter != null;
 
-        public async Task RunAsync(string identifier, MqttApplicationMessage willApplicationMessage, IMqttCommunicationAdapter adapter)
+        public async Task RunAsync(MqttApplicationMessage willMessage, IMqttCommunicationAdapter adapter)
         {
             if (adapter == null) throw new ArgumentNullException(nameof(adapter));
 
-            _willApplicationMessage = willApplicationMessage;
+            _willMessage = willMessage;
 
             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);
-                }
+                _pendingMessagesQueue.Start(adapter, _cancellationTokenSource.Token);
+                await ReceivePacketsAsync(adapter, _cancellationTokenSource.Token);
             }
-            catch (MqttCommunicationException)
+            catch (OperationCanceledException)
             {
             }
+            catch (MqttCommunicationException exception)
+            {
+                MqttNetTrace.Warning(nameof(MqttClientSession), exception, "Client '{0}': Communication exception while processing client packets.", ClientId);
+            }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttClientSession), exception, $"Client '{_identifier}': Unhandled exception while processing client packets.");
+                MqttNetTrace.Error(nameof(MqttClientSession), exception, "Client '{0}': Unhandled exception while processing client packets.", ClientId);
             }
-            finally
+        }
+
+        public void Stop()
+        {
+            if (_willMessage != null)
             {
-                if (willApplicationMessage != null)
-                {
-                    _publishPacketReceivedCallback(this, _willApplicationMessage.ToPublishPacket());
-                }
-
-                _messageQueue.Stop();
-                _cancellationTokenSource.Cancel();
-                Adapter = null;
-
-                MqttTrace.Information(nameof(MqttClientSession), $"Client '{_identifier}': Disconnected.");
+                _mqttClientSessionsManager.DispatchPublishPacket(this, _willMessage.ToPublishPacket());
             }
+
+            _cancellationTokenSource?.Cancel(false);
+            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
+
+            _adapter = null;
+
+            MqttNetTrace.Information(nameof(MqttClientSession), "Client '{0}': Disconnected.", ClientId);
         }
 
         public void EnqueuePublishPacket(MqttPublishPacket publishPacket)
@@ -89,8 +91,8 @@ namespace MQTTnet.Core.Server
                 return;
             }
 
-            _messageQueue.Enqueue(publishPacket);
-            MqttTrace.Verbose(nameof(MqttClientSession), $"Client '{_identifier}: Enqueued pending publish packet.");
+            _pendingMessagesQueue.Enqueue(publishPacket);
+            MqttNetTrace.Verbose(nameof(MqttClientSession), "Client '{0}': Enqueued pending publish packet.", ClientId);
         }
 
         public void Dispose()
@@ -99,68 +101,100 @@ namespace MQTTnet.Core.Server
             _cancellationTokenSource?.Dispose();
         }
 
-        private Task HandleIncomingPacketAsync(MqttBasePacket packet)
+        private async Task ReceivePacketsAsync(IMqttCommunicationAdapter adapter, CancellationToken cancellationToken)
+        {
+            try
+            {
+                while (!cancellationToken.IsCancellationRequested)
+                {
+                    var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
+                    await ProcessReceivedPacketAsync(adapter, packet).ConfigureAwait(false);
+                }
+            }
+            catch (OperationCanceledException)
+            {
+            }
+            catch (MqttCommunicationException exception)
+            {
+                MqttNetTrace.Warning(nameof(MqttClientSession), exception, "Client '{0}': Communication exception while processing client packets.", ClientId);
+                Stop();
+            }
+            catch (Exception exception)
+            {
+                MqttNetTrace.Error(nameof(MqttClientSession), exception, "Client '{0}': Unhandled exception while processing client packets.", ClientId);
+                Stop();
+            }
+        }
+
+        private async Task ProcessReceivedPacketAsync(IMqttCommunicationAdapter adapter, MqttBasePacket packet)
         {
             if (packet is MqttSubscribePacket subscribePacket)
             {
-                return Adapter.SendPacketAsync(_subscriptionsManager.Subscribe(subscribePacket), _options.DefaultCommunicationTimeout);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Subscribe(subscribePacket));
+                EnqueueRetainedMessages(subscribePacket);
             }
-
-            if (packet is MqttUnsubscribePacket unsubscribePacket)
+            else if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                return Adapter.SendPacketAsync(_subscriptionsManager.Unsubscribe(unsubscribePacket), _options.DefaultCommunicationTimeout);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Unsubscribe(unsubscribePacket));
             }
-
-            if (packet is MqttPublishPacket publishPacket)
+            else if (packet is MqttPublishPacket publishPacket)
             {
-                return HandleIncomingPublishPacketAsync(publishPacket);
+                await HandleIncomingPublishPacketAsync(adapter, publishPacket);
             }
-
-            if (packet is MqttPubRelPacket pubRelPacket)
+            else if (packet is MqttPubRelPacket pubRelPacket)
             {
-                return HandleIncomingPubRelPacketAsync(pubRelPacket);
+                await HandleIncomingPubRelPacketAsync(adapter, pubRelPacket);
             }
-
-            if (packet is MqttPubRecPacket pubRecPacket)
+            else if (packet is MqttPubRecPacket pubRecPacket)
             {
-                return Adapter.SendPacketAsync(pubRecPacket.CreateResponse<MqttPubRelPacket>(), _options.DefaultCommunicationTimeout);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, pubRecPacket.CreateResponse<MqttPubRelPacket>());
             }
-
-            if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
+            else if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
             {
                 // Discard message.
-                return Task.FromResult((object)null);
             }
-
-            if (packet is MqttPingReqPacket)
+            else if (packet is MqttPingReqPacket)
             {
-                return Adapter.SendPacketAsync(new MqttPingRespPacket(), _options.DefaultCommunicationTimeout);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPingRespPacket());
             }
-
-            if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
+            else if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
             {
-                _cancellationTokenSource.Cancel();
-                return Task.FromResult((object)null);
+                Stop();
+            }
+            else
+            {
+                MqttNetTrace.Warning(nameof(MqttClientSession), "Client '{0}': Received not supported packet ({1}). Closing connection.", ClientId, packet);
+                Stop();
             }
-
-            MqttTrace.Warning(nameof(MqttClientSession), $"Client '{_identifier}': Received not supported packet ({packet}). Closing connection.");
-            _cancellationTokenSource.Cancel();
-
-            return Task.FromResult((object)null);
         }
 
-        private Task HandleIncomingPublishPacketAsync(MqttPublishPacket publishPacket)
+        private void EnqueueRetainedMessages(MqttSubscribePacket subscribePacket)
         {
+            var retainedMessages = _mqttClientSessionsManager.RetainedMessagesManager.GetMessages(subscribePacket);
+            foreach (var publishPacket in retainedMessages)
+            {
+                EnqueuePublishPacket(publishPacket);
+            }
+        }
+
+        private async Task HandleIncomingPublishPacketAsync(IMqttCommunicationAdapter adapter, MqttPublishPacket publishPacket)
+        {
+            if (publishPacket.Retain)
+            {
+                await _mqttClientSessionsManager.RetainedMessagesManager.HandleMessageAsync(ClientId, publishPacket);
+            }
+
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
-                _publishPacketReceivedCallback(this, publishPacket);
-                return Task.FromResult(0);
+                _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
-                _publishPacketReceivedCallback(this, publishPacket);
-                return Adapter.SendPacketAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
@@ -171,22 +205,23 @@ namespace MQTTnet.Core.Server
                     _unacknowledgedPublishPackets.Add(publishPacket.PacketIdentifier);
                 }
 
-                _publishPacketReceivedCallback(this, publishPacket);
+                _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
 
-                return Adapter.SendPacketAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             throw new MqttCommunicationException("Received a not supported QoS level.");
         }
 
-        private Task HandleIncomingPubRelPacketAsync(MqttPubRelPacket pubRelPacket)
+        private Task HandleIncomingPubRelPacketAsync(IMqttCommunicationAdapter adapter, MqttPubRelPacket pubRelPacket)
         {
             lock (_unacknowledgedPublishPackets)
             {
                 _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;
@@ -8,86 +9,133 @@ using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Serializer;
 
 namespace MQTTnet.Core.Server
 {
     public sealed class MqttClientSessionsManager
     {
-        private readonly object _syncRoot = new object();
         private readonly Dictionary<string, MqttClientSession> _clientSessions = new Dictionary<string, MqttClientSession>();
         private readonly MqttServerOptions _options;
 
         public MqttClientSessionsManager(MqttServerOptions options)
         {
             _options = options ?? throw new ArgumentNullException(nameof(options));
+            RetainedMessagesManager = new MqttClientRetainedMessagesManager(options);
         }
 
         public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        public event EventHandler<MqttClientDisconnectedEventArgs> ClientDisconnected;
 
-        public async Task RunClientSessionAsync(MqttClientConnectedEventArgs eventArgs)
+        public MqttClientRetainedMessagesManager RetainedMessagesManager { get; }
+
+        public async Task RunClientSessionAsync(IMqttCommunicationAdapter clientAdapter)
         {
+            var clientId = string.Empty;
             try
             {
-                var connectPacket = await eventArgs.ClientAdapter.ReceivePacketAsync(_options.DefaultCommunicationTimeout) as MqttConnectPacket;
-                if (connectPacket == null)
+                if (!(await 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;
+                clientId = connectPacket.ClientId;
 
+                // Switch to the required protocol version before sending any response.
+                clientAdapter.PacketSerializer.ProtocolVersion = connectPacket.ProtocolVersion;
+                
                 var connectReturnCode = ValidateConnection(connectPacket);
                 if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
                 {
-                    await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                    await 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 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);
+                ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(new ConnectedMqttClient
+                {
+                    ClientId = clientId,
+                    ProtocolVersion = clientAdapter.PacketSerializer.ProtocolVersion
+                }));
+
+                await clientSession.Session.RunAsync(connectPacket.WillMessage, clientAdapter).ConfigureAwait(false);
             }
             catch (Exception exception)
             {
-                MqttTrace.Error(nameof(MqttServer), exception, exception.Message);
+                MqttNetTrace.Error(nameof(MqttServer), exception, exception.Message);
             }
             finally
             {
-                await eventArgs.ClientAdapter.DisconnectAsync();
+                try
+                {
+                    await clientAdapter.DisconnectAsync(_options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                }
+                catch (Exception)
+                {
+                    //ignored
+                }
+
+                ClientDisconnected?.Invoke(this, new MqttClientDisconnectedEventArgs(new ConnectedMqttClient
+                {
+                    ClientId = clientId,
+                    ProtocolVersion = clientAdapter.PacketSerializer.ProtocolVersion
+                }));
             }
         }
 
         public void Clear()
         {
-            lock (_syncRoot)
+            lock (_clientSessions)
             {
                 _clientSessions.Clear();
             }
         }
 
-        public IList<ConnectedMqttClient> GetConnectedClients()
+        public IReadOnlyList<ConnectedMqttClient> GetConnectedClients()
         {
-            lock (_syncRoot)
+            lock (_clientSessions)
             {
                 return _clientSessions.Where(s => s.Value.IsConnected).Select(s => new ConnectedMqttClient
                 {
                     ClientId = s.Value.ClientId,
-                    ProtocolVersion = s.Value.Adapter.PacketSerializer.ProtocolVersion
+                    ProtocolVersion = s.Value.ProtocolVersion ?? MqttProtocolVersion.V311
                 }).ToList();
             }
         }
 
+        public void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        {
+            try
+            {
+                var eventArgs = new MqttApplicationMessageReceivedEventArgs(senderClientSession?.ClientId, publishPacket.ToApplicationMessage());
+                ApplicationMessageReceived?.Invoke(this, eventArgs);
+            }
+            catch (Exception exception)
+            {
+                MqttNetTrace.Error(nameof(MqttClientSessionsManager), exception, "Error while processing application message");
+            }
+
+            lock (_clientSessions)
+            {
+                foreach (var clientSession in _clientSessions.Values.ToList())
+                {
+                    clientSession.EnqueuePublishPacket(publishPacket);
+                }
+            }
+        }
+
         private MqttConnectReturnCode ValidateConnection(MqttConnectPacket connectPacket)
         {
             if (_options.ConnectionValidator != null)
@@ -100,10 +148,9 @@ namespace MQTTnet.Core.Server
 
         private GetOrCreateClientSessionResult GetOrCreateClientSession(MqttConnectPacket connectPacket)
         {
-            lock (_syncRoot)
+            lock (_clientSessions)
             {
-                MqttClientSession clientSession;
-                var isSessionPresent = _clientSessions.TryGetValue(connectPacket.ClientId, out clientSession);
+                var isSessionPresent = _clientSessions.TryGetValue(connectPacket.ClientId, out var clientSession);
                 if (isSessionPresent)
                 {
                     if (connectPacket.CleanSession)
@@ -111,11 +158,11 @@ namespace MQTTnet.Core.Server
                         _clientSessions.Remove(connectPacket.ClientId);
                         clientSession.Dispose();
                         clientSession = null;
-                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Disposed existing session of client '{connectPacket.ClientId}'.");
+                        MqttNetTrace.Verbose(nameof(MqttClientSessionsManager), "Disposed existing session of client '{0}'.", connectPacket.ClientId);
                     }
                     else
                     {
-                        MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Reusing existing session of client '{connectPacket.ClientId}'.");
+                        MqttNetTrace.Verbose(nameof(MqttClientSessionsManager), "Reusing existing session of client '{0}'.", connectPacket.ClientId);
                     }
                 }
 
@@ -124,35 +171,14 @@ namespace MQTTnet.Core.Server
                 {
                     isExistingSession = false;
 
-                    clientSession = new MqttClientSession(connectPacket.ClientId, _options, DispatchPublishPacket);
+                    clientSession = new MqttClientSession(connectPacket.ClientId, _options, this);
                     _clientSessions[connectPacket.ClientId] = clientSession;
 
-                    MqttTrace.Verbose(nameof(MqttClientSessionsManager), $"Created a new session for client '{connectPacket.ClientId}'.");
+                    MqttNetTrace.Verbose(nameof(MqttClientSessionsManager), "Created a new session for client '{0}'.", connectPacket.ClientId);
                 }
 
                 return new GetOrCreateClientSessionResult { IsExistingSession = isExistingSession, Session = clientSession };
             }
         }
-
-        public void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
-        {
-            try
-            {
-                var eventArgs = new MqttApplicationMessageReceivedEventArgs(senderClientSession?.ClientId, publishPacket.ToApplicationMessage());
-                ApplicationMessageReceived?.Invoke(this, eventArgs);
-            }
-            catch (Exception exception)
-            {
-                MqttTrace.Error(nameof(MqttClientSessionsManager), exception, "Error while processing application message");
-            }
-
-            lock (_syncRoot)
-            {
-                foreach (var clientSession in _clientSessions.Values.ToList())
-                {
-                    clientSession.EnqueuePublishPacket(publishPacket);
-                }
-            }
-        }
     }
 }

MQTTnet.Core/Server/MqttServer.cs

@@ -20,18 +20,20 @@ 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);
+            _clientSessionsManager.ClientConnected += OnClientConnected;
+            _clientSessionsManager.ClientDisconnected += OnClientDisconnected;
         }
 
-        public IList<ConnectedMqttClient> GetConnectedClients()
+        public IReadOnlyList<ConnectedMqttClient> GetConnectedClients()
         {
             return _clientSessionsManager.GetConnectedClients();
         }
 
         public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
-
+        public event EventHandler<MqttClientDisconnectedEventArgs> ClientDisconnected;
         public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
 
         public void Publish(MqttApplicationMessage applicationMessage)
@@ -41,31 +43,24 @@ namespace MQTTnet.Core.Server
             _clientSessionsManager.DispatchPublishPacket(null, applicationMessage.ToPublishPacket());
         }
 
-        public void InjectClient(string identifier, IMqttCommunicationAdapter adapter)
-        {
-            if (adapter == null) throw new ArgumentNullException(nameof(adapter));
-
-            if (_cancellationTokenSource == null) throw new InvalidOperationException("The MQTT server is not started.");
-
-            OnClientConnected(this, new MqttClientConnectedEventArgs(identifier, adapter));
-        }
-
-        public void Start()
+        public async Task StartAsync()
         {
             if (_cancellationTokenSource != null) throw new InvalidOperationException("The MQTT server is already started.");
 
             _cancellationTokenSource = new CancellationTokenSource();
 
+            await _clientSessionsManager.RetainedMessagesManager.LoadMessagesAsync();
+
             foreach (var adapter in _adapters)
             {
-                adapter.ClientConnected += OnClientConnected;
-                adapter.Start(_options);
+                adapter.ClientAccepted += OnClientAccepted;
+                await adapter.StartAsync(_options);
             }
-            
-            MqttTrace.Information(nameof(MqttServer), "Started.");
+
+            MqttNetTrace.Information(nameof(MqttServer), "Started.");
         }
 
-        public void Stop()
+        public async Task StopAsync()
         {
             _cancellationTokenSource?.Cancel(false);
             _cancellationTokenSource?.Dispose();
@@ -73,21 +68,30 @@ namespace MQTTnet.Core.Server
 
             foreach (var adapter in _adapters)
             {
-                adapter.ClientConnected -= OnClientConnected;
-                adapter.Stop();
+                adapter.ClientAccepted -= OnClientAccepted;
+                await adapter.StopAsync();
             }
 
             _clientSessionsManager.Clear();
 
-            MqttTrace.Information(nameof(MqttServer), "Stopped.");
+            MqttNetTrace.Information(nameof(MqttServer), "Stopped.");
+        }
+
+        private void OnClientAccepted(IMqttCommunicationAdapter adapter)
+        {
+            Task.Run(() =>_clientSessionsManager.RunClientSessionAsync(adapter), _cancellationTokenSource.Token);
         }
 
         private void OnClientConnected(object sender, MqttClientConnectedEventArgs eventArgs)
         {
-            MqttTrace.Information(nameof(MqttServer), $"Client '{eventArgs.Identifier}': Connected.");
+            MqttNetTrace.Information(nameof(MqttServer), "Client '{0}': Connected.", eventArgs.Client.ClientId);
             ClientConnected?.Invoke(this, eventArgs);
+        }
 
-            Task.Run(() => _clientSessionsManager.RunClientSessionAsync(eventArgs), _cancellationTokenSource.Token);
+        private void OnClientDisconnected(object sender, MqttClientDisconnectedEventArgs eventArgs)
+        {
+            MqttNetTrace.Information(nameof(MqttServer), "Client '{0}': Disconnected.", eventArgs.Client.ClientId);
+            ClientDisconnected?.Invoke(this, eventArgs);
         }
     }
 }

MQTTnet.Core/Server/MqttServerOptions.cs

@@ -9,11 +9,13 @@ 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);
 
         public Func<MqttConnectPacket, MqttConnectReturnCode> ConnectionValidator { get; set; }
+
+        public IMqttServerStorage Storage { get; set; }
     }
 }

MQTTnet.sln

@@ -1,9 +1,9 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26730.8
+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}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Core.Tests", "Tests\MQTTnet.Core.Tests\MQTTnet.Core.Tests.csproj", "{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MQTTnet.NetFramework", "Frameworks\MQTTnet.NetFramework\MQTTnet.NetFramework.csproj", "{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}"
 EndProject
@@ -32,6 +32,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		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
@@ -48,18 +50,18 @@ Global
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|ARM.ActiveCfg = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|ARM.Build.0 = Debug|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.ActiveCfg = Debug|x64
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.Build.0 = Debug|x64
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.ActiveCfg = Debug|x86
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.Build.0 = Debug|x86
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x64.Build.0 = Debug|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Debug|x86.Build.0 = Debug|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|Any CPU.Build.0 = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|ARM.ActiveCfg = Release|Any CPU
 		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|ARM.Build.0 = Release|Any CPU
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.ActiveCfg = Release|x64
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.Build.0 = Release|x64
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.ActiveCfg = Release|x86
-		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.Build.0 = Release|x86
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.ActiveCfg = Release|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x64.Build.0 = Release|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.ActiveCfg = Release|Any CPU
+		{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}.Release|x86.Build.0 = Release|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A480EF90-0EAA-4D9A-B271-47A9C47F6F7D}.Debug|ARM.ActiveCfg = Debug|Any CPU
@@ -162,6 +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
@@ -173,6 +191,7 @@ 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}

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

@@ -3,30 +3,36 @@
 </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 (broker). The implementation is based on the documentation from http://mqtt.org/.
 
 # Features
 
-## General
+### General
 * Async support
 * TLS 1.2 support for client and server (but not UWP servers)
-* Extensible communication channels (i.e. In-Memory, TCP, TCP+SSL, WebSockets (not included in this project))
-* Interfaces included for mocking and testing
+* 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 (50+ tests)
+* Unit tested (62+ tests)
 
-## Client
+\* 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)
+### 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
+* Retained messages are supported including persisting via interface methods (own implementation required)
 
 # Supported frameworks
 * .NET Standard 1.3+
@@ -34,6 +40,7 @@ MQTTnet is a .NET library for MQTT based communication. It provides a MQTT clien
 * .NET Core App 1.1+
 * .NET Framework 4.5.2+ (x86, x64, AnyCPU)
 * Universal Windows (UWP) 10.0.10240+ (x86, x64, ARM, AnyCPU)
+* Mono 5.2+
 
 # Supported MQTT versions
 * 3.1.1
@@ -42,6 +49,9 @@ MQTTnet is a .NET library for MQTT based communication. It provides a MQTT clien
 # Nuget
 This library is available as a nuget package: https://www.nuget.org/packages/MQTTnet/
 
+# Examples
+Please find examples and the documentation at the Wiki of this repository (https://github.com/chkr1011/MQTTnet/wiki).
+
 # Contributions
 If you want to contribute to this project just create a pull request.
 
@@ -51,105 +61,4 @@ This library is used in the following projects:
 * MQTT Client Rx (Wrapper for Reactive Extensions, https://github.com/1iveowl/MQTTClient.rx)
 * HA4IoT (Open Source Home Automation system for .NET, https://github.com/chkr1011/HA4IoT)
 
-If you use this library and want to see your project here please let me know.
-
-# Examples
-## MqttClient
-
-```csharp
-var options = new MqttClientOptions
-{
-    Server = "localhost"
-};
-
-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
-{
-    Console.WriteLine("### CONNECTING FAILED ###");
-}
-
-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);
-}
-```
-
-## MqttServer
-
-```csharp
-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();
-```
+If you use this library and want to see your project here please let me know.

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

@@ -1,114 +1,20 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+<Project Sdk="Microsoft.NET.Sdk">
+
   <PropertyGroup>
-    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
-    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
-    <ProjectGuid>{A7FF0C91-25DE-4BA6-B39E-F54E8DADF1CC}</ProjectGuid>
-    <OutputType>Library</OutputType>
-    <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>MQTTnet.Core.Tests</RootNamespace>
-    <AssemblyName>MQTTnet.Core.Tests</AssemblyName>
-    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
-    <FileAlignment>512</FileAlignment>
-    <TargetFrameworkProfile />
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
-    <DebugSymbols>true</DebugSymbols>
-    <DebugType>full</DebugType>
-    <Optimize>false</Optimize>
-    <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>DEBUG;TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
-    <DebugType>pdbonly</DebugType>
-    <Optimize>true</Optimize>
-    <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|AnyCPU'">
-    <OutputPath>bin\Any CPU\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <Optimize>true</Optimize>
-    <DebugType>pdbonly</DebugType>
-    <PlatformTarget>AnyCPU</PlatformTarget>
-    <ErrorReport>prompt</ErrorReport>
-    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x64'">
-    <DebugSymbols>true</DebugSymbols>
-    <OutputPath>bin\x64\Debug\</OutputPath>
-    <DefineConstants>DEBUG;TRACE</DefineConstants>
-    <DebugType>full</DebugType>
-    <PlatformTarget>x64</PlatformTarget>
-    <ErrorReport>prompt</ErrorReport>
-    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x64'">
-    <OutputPath>bin\x64\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <Optimize>true</Optimize>
-    <DebugType>pdbonly</DebugType>
-    <PlatformTarget>x64</PlatformTarget>
-    <ErrorReport>prompt</ErrorReport>
-    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x64'">
-    <OutputPath>bin\x64\Any CPU\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <Optimize>true</Optimize>
-    <DebugType>pdbonly</DebugType>
-    <PlatformTarget>x64</PlatformTarget>
-    <ErrorReport>prompt</ErrorReport>
-    <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|x86'">
-    <PlatformTarget>x86</PlatformTarget>
-    <OutputPath>bin\x86\Debug\</OutputPath>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release|x86'">
-    <PlatformTarget>x86</PlatformTarget>
-    <OutputPath>bin\x86\Release\</OutputPath>
-  </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Any CPU|x86'">
-    <PlatformTarget>x86</PlatformTarget>
-    <OutputPath>bin\x86\Any CPU\</OutputPath>
+    <OutputType>Exe</OutputType>
+    <DebugType>Full</DebugType>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
   </PropertyGroup>
+
   <ItemGroup>
-    <Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
+    <PackageReference Include="MSTest.TestAdapter" Version="1.1.18" />
+    <PackageReference Include="MSTest.TestFramework" Version="1.1.18" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
   </ItemGroup>
+
   <ItemGroup>
-    <Compile Include="ByteReaderTests.cs" />
-    <Compile Include="ByteWriterTests.cs" />
-    <Compile Include="MqttPacketSerializerTests.cs" />
-    <Compile Include="MqttServerTests.cs" />
-    <Compile Include="MqttSubscriptionsManagerTests.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="TestMqttCommunicationAdapter.cs" />
-    <Compile Include="TestMqttServerAdapter.cs" />
-    <Compile Include="TopicFilterComparerTests.cs" />
+    <ProjectReference Include="..\..\Frameworks\MQTTnet.Netstandard\MQTTnet.NetStandard.csproj" />
+    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj" />
   </ItemGroup>
-  <ItemGroup>
-    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
-  </ItemGroup>
-  <ItemGroup>
-    <ProjectReference Include="..\..\MQTTnet.Core\MQTTnet.Core.csproj">
-      <Project>{2ecb99e4-72d0-4c23-99ba-93d511d3967d}</Project>
-      <Name>MQTTnet.Core</Name>
-    </ProjectReference>
-  </ItemGroup>
-  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
-       Other similar extension points exist, see Microsoft.Common.targets.
-  <Target Name="BeforeBuild">
-  </Target>
-  <Target Name="AfterBuild">
-  </Target>
-  -->
+
 </Project>

Tests/MQTTnet.Core.Tests/MqttCommunicationAdapterFactory.cs

@@ -0,0 +1,20 @@
+using MQTTnet.Core.Adapter;
+using MQTTnet.Core.Client;
+
+namespace MQTTnet.Core.Tests
+{
+    public class MqttCommunicationAdapterFactory : IMqttCommunicationAdapterFactory
+    {
+        private readonly IMqttCommunicationAdapter _adapter;
+
+        public MqttCommunicationAdapterFactory(IMqttCommunicationAdapter adapter)
+        {
+            _adapter = adapter;
+        }
+
+        public IMqttCommunicationAdapter CreateMqttCommunicationAdapter(MqttClientOptions options)
+        {
+            return _adapter;
+        }
+    }
+}

Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs

@@ -1,10 +1,11 @@
 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;
 using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Serializer;
@@ -391,6 +392,12 @@ 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()
@@ -403,24 +410,14 @@ namespace MQTTnet.Core.Tests
                 _stream.Position = 0;
             }
 
-            public async Task ConnectAsync(MqttClientOptions options)
+            public Task ConnectAsync()
             {
-                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()
@@ -429,32 +426,32 @@ namespace MQTTnet.Core.Tests
             }
         }
 
-        private void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
+        private static void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
             var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
-            var channel = new TestChannel();
-            serializer.SerializeAsync(packet, channel).Wait();
-            var buffer = channel.ToArray();
+            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 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

@@ -13,47 +13,48 @@ 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]
         public async Task MqttServer_WillMessage()
         {
-            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
-            s.Start();
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
 
             var willMessage = new MqttApplicationMessage("My/last/will", new byte[0], MqttQualityOfServiceLevel.AtMostOnce, false);
-            var c1 = ConnectTestClient("c1", null, s);
-            var c2 = ConnectTestClient("c2", willMessage, s);
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2", willMessage);
 
             var receivedMessagesCount = 0;
             c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
@@ -63,7 +64,7 @@ namespace MQTTnet.Core.Tests
 
             await Task.Delay(1000);
 
-            s.Stop();
+            await s.StopAsync();
 
             Assert.AreEqual(1, receivedMessagesCount);
         }
@@ -71,15 +72,16 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public async Task MqttServer_Unsubscribe()
         {
-            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
-            s.Start();
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
 
-            var c1 = ConnectTestClient("c1", null, s);
-            var c2 = ConnectTestClient("c2", null, s);
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
 
             var receivedMessagesCount = 0;
             c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
-            
+
             var message = new MqttApplicationMessage("a", new byte[0], MqttQualityOfServiceLevel.AtLeastOnce, false);
 
             await c2.PublishAsync(message);
@@ -91,13 +93,13 @@ 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);
             Assert.AreEqual(1, receivedMessagesCount);
 
-            s.Stop();
+            await s.StopAsync();
             await Task.Delay(500);
 
             Assert.AreEqual(1, receivedMessagesCount);
@@ -106,10 +108,11 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public async Task MqttServer_Publish()
         {
-            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
-            s.Start();
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
 
-            var c1 = ConnectTestClient("c1", null, s);
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
 
             var receivedMessagesCount = 0;
             c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
@@ -120,36 +123,140 @@ namespace MQTTnet.Core.Tests
             s.Publish(message);
             await Task.Delay(500);
 
-            s.Stop();
+            await s.StopAsync();
 
             Assert.AreEqual(1, receivedMessagesCount);
         }
 
-        private static MqttClient ConnectTestClient(string clientId, MqttApplicationMessage willMessage, MqttServer server)
+        [TestMethod]
+        public async Task MqttServer_NoRetainedMessage()
         {
-            var adapterA = new TestMqttCommunicationAdapter();
-            var adapterB = new TestMqttCommunicationAdapter();
-            adapterA.Partner = adapterB;
-            adapterB.Partner = adapterA;
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
 
-            var client = new MqttClient(new MqttClientOptions(), adapterA);
-            server.InjectClient(clientId, adapterB);
-            client.ConnectAsync(willMessage).Wait();
-            return client;
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            await c1.PublishAsync(new MqttApplicationMessage("retained", new byte[3], MqttQualityOfServiceLevel.AtLeastOnce, false));
+            await c1.DisconnectAsync();
+
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
+            var receivedMessagesCount = 0;
+            c2.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+            await c2.SubscribeAsync(new TopicFilter("retained", MqttQualityOfServiceLevel.AtLeastOnce));
+
+            await Task.Delay(500);
+
+            await s.StopAsync();
+
+            Assert.AreEqual(0, receivedMessagesCount);
         }
 
-        private async Task TestPublishAsync(
+        [TestMethod]
+        public async Task MqttServer_RetainedMessage()
+        {
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
+
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            await c1.PublishAsync(new MqttApplicationMessage("retained", new byte[3], MqttQualityOfServiceLevel.AtLeastOnce, true));
+            await c1.DisconnectAsync();
+
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
+            var receivedMessagesCount = 0;
+            c2.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+            await c2.SubscribeAsync(new TopicFilter("retained", MqttQualityOfServiceLevel.AtLeastOnce));
+
+            await Task.Delay(500);
+
+            await s.StopAsync();
+
+            Assert.AreEqual(1, receivedMessagesCount);
+        }
+
+        [TestMethod]
+        public async Task MqttServer_ClearRetainedMessage()
+        {
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
+
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            await c1.PublishAsync(new MqttApplicationMessage("retained", new byte[3], MqttQualityOfServiceLevel.AtLeastOnce, true));
+            await c1.PublishAsync(new MqttApplicationMessage("retained", new byte[0], MqttQualityOfServiceLevel.AtLeastOnce, true));
+            await c1.DisconnectAsync();
+
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
+            var receivedMessagesCount = 0;
+            c2.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+            await c2.SubscribeAsync(new TopicFilter("retained", MqttQualityOfServiceLevel.AtLeastOnce));
+
+            await Task.Delay(500);
+
+            await s.StopAsync();
+
+            Assert.AreEqual(0, receivedMessagesCount);
+        }
+
+        [TestMethod]
+        public async Task MqttServer_PersistRetainedMessage()
+        {
+            var storage = new TestStorage();
+
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions { Storage = storage }, new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
+
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            await c1.PublishAsync(new MqttApplicationMessage("retained", new byte[3], MqttQualityOfServiceLevel.AtLeastOnce, true));
+            await c1.DisconnectAsync();
+
+            await s.StopAsync();
+
+            s = new MqttServer(new MqttServerOptions { Storage = storage }, new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
+
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
+            var receivedMessagesCount = 0;
+            c2.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
+            await c2.SubscribeAsync(new TopicFilter("retained", MqttQualityOfServiceLevel.AtLeastOnce));
+
+            await Task.Delay(500);
+
+            await s.StopAsync();
+
+            Assert.AreEqual(1, receivedMessagesCount);
+        }
+
+        private class TestStorage : IMqttServerStorage
+        {
+            private IList<MqttApplicationMessage> _messages = new List<MqttApplicationMessage>();
+
+            public Task SaveRetainedMessagesAsync(IList<MqttApplicationMessage> messages)
+            {
+                _messages = messages;
+                return Task.FromResult(0);
+            }
+
+            public Task<IList<MqttApplicationMessage>> LoadRetainedMessagesAsync()
+            {
+                return Task.FromResult(_messages);
+            }
+        }
+
+        private static async Task TestPublishAsync(
             string topic,
             MqttQualityOfServiceLevel qualityOfServiceLevel,
             string topicFilter,
             MqttQualityOfServiceLevel filterQualityOfServiceLevel,
             int expectedReceivedMessagesCount)
         {
-            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { new TestMqttServerAdapter() });
-            s.Start();
+            var serverAdapter = new TestMqttServerAdapter();
+            var s = new MqttServer(new MqttServerOptions(), new List<IMqttServerAdapter> { serverAdapter });
+            await s.StartAsync();
 
-            var c1 = ConnectTestClient("c1", null, s);
-            var c2 = ConnectTestClient("c2", null, s);
+            var c1 = await serverAdapter.ConnectTestClient(s, "c1");
+            var c2 = await serverAdapter.ConnectTestClient(s, "c2");
 
             var receivedMessagesCount = 0;
             c1.ApplicationMessageReceived += (_, __) => receivedMessagesCount++;
@@ -158,11 +265,11 @@ 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);
 
-            s.Stop();
+            await s.StopAsync();
 
             Assert.AreEqual(expectedReceivedMessagesCount, receivedMessagesCount);
         }

Tests/MQTTnet.Core.Tests/Properties/AssemblyInfo.cs

@@ -1,15 +0,0 @@
-using System.Reflection;
-using System.Runtime.InteropServices;
-
-[assembly: AssemblyTitle("MQTTnet.Core.Tests")]
-[assembly: AssemblyDescription("")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("Christian Kratky")]
-[assembly: AssemblyProduct("MQTTnet")]
-[assembly: AssemblyCopyright("Copyright © Christian Kratky 2016-2017")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-[assembly: ComVisible(false)]
-[assembly: Guid("a7ff0c91-25de-4ba6-b39e-f54e8dadf1cc")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]

Tests/MQTTnet.Core.Tests/TestMqttCommunicationAdapter.cs

@@ -1,8 +1,9 @@
 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;
 
@@ -16,29 +17,33 @@ namespace MQTTnet.Core.Tests
 
         public IMqttPacketSerializer PacketSerializer { get; } = new MqttPacketSerializer();
 
-        public async Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
+        public Task ConnectAsync(TimeSpan timeout)
         {
-            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.Core.Tests/TestMqttServerAdapter.cs

@@ -1,24 +1,63 @@
 using System;
+using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Server;
+using MQTTnet.Core.Client;
 
 namespace MQTTnet.Core.Tests
 {
     public class TestMqttServerAdapter : IMqttServerAdapter
     {
-        public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
+        public event Action<IMqttCommunicationAdapter> ClientAccepted;
 
-        public void FireClientConnectedEvent(MqttClientConnectedEventArgs eventArgs)
+        public async Task<MqttClient> ConnectTestClient(IMqttServer server, string clientId, MqttApplicationMessage willMessage = null)
         {
-            ClientConnected?.Invoke(this, eventArgs);
+            var adapterA = new TestMqttCommunicationAdapter();
+            var adapterB = new TestMqttCommunicationAdapter();
+            adapterA.Partner = adapterB;
+            adapterB.Partner = adapterA;
+
+            var client = new MqttClient(new MqttCommunicationAdapterFactory(adapterA));
+            var connected = WaitForClientToConnect(server, clientId);
+
+            FireClientAcceptedEvent(adapterB);
+            await client.ConnectAsync(new MqttClientTcpOptions { ClientId = clientId, WillMessage = willMessage });
+            await connected;
+
+            return client;
+        }
+        
+        private static Task WaitForClientToConnect(IMqttServer s, string clientId)
+        {
+            var tcs = new TaskCompletionSource<object>();
+
+            void Handler(object sender, MqttClientConnectedEventArgs args)
+            {
+                if (args.Client.ClientId == clientId)
+                {
+                    s.ClientConnected -= Handler;
+                    tcs.SetResult(null);
+                }
+            }
+
+            s.ClientConnected += Handler;
+
+            return tcs.Task;
         }
 
-        public void Start(MqttServerOptions options)
+        private void FireClientAcceptedEvent(IMqttCommunicationAdapter adapter)
         {
+            ClientAccepted?.Invoke(adapter);
         }
 
-        public void Stop()
-        {                 
+        public Task StartAsync(MqttServerOptions options)
+        {
+            return Task.FromResult(0);
+        }
+
+        public Task StopAsync()
+        {
+            return Task.FromResult(0);
         }
     }
 }

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 +1,170 @@
+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)
+        {
+
+            MqttNetTrace.TraceMessagePublished += (s, e) =>
+            {
+                Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
+                if (e.Exception != null)
+                {
+                    Console.WriteLine(e.Exception);
+                }
+            };
+
+            try
+            {
+                var options = new MqttClientWebSocketOptions
+                {
+                    Uri = "localhost",
+                    ClientId = "XYZ",
+                    CleanSession = true
+                };
+
+                var client = new MqttClientFactory().CreateMqttClient();
+                client.ApplicationMessageReceived += (s, e) =>
+                {
+                    Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
+                    Console.WriteLine($"+ 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(options);
+                    }
+                    catch
+                    {
+                        Console.WriteLine("### RECONNECTING FAILED ###");
+                    }
+                };
+
+                try
+                {
+                    await client.ConnectAsync(options);
+                }
+                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)
+        {
+            MqttNetTrace.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.StartAsync();
+
+                Console.WriteLine("Press any key to exit.");
+                Console.ReadLine();
+
+                mqttServer.StopAsync();
+            }
+            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 MqttClientTcpOptions
+                {
+                    Server = "localhost",
+                    ClientId = "XYZ",
+                    CleanSession = true,
+                    DefaultCommunicationTimeout = TimeSpan.FromMinutes(10)
+                };
+
+                var client = new MqttClientFactory().CreateMqttClient();
+                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(options);
+                    }
+                    catch
+                    {
+                        Console.WriteLine("### RECONNECTING FAILED ###");
+                    }
+                };
+
+                try
+                {
+                    await client.ConnectAsync(options);
+                }
+                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 async Task 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();
+                    }
+                };
+                await mqttServer.StartAsync();
+
+                Console.WriteLine("Press any key to exit.");
+                Console.ReadLine();
+
+                await mqttServer.StopAsync();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            Console.ReadLine();
+        }
+    }
+}

Tests/MQTTnet.TestApp.NetFramework/Program.cs

@@ -9,6 +9,7 @@ using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Server;
+using MQTTnet.Implementations;
 
 namespace MQTTnet.TestApp.NetFramework
 {
@@ -19,6 +20,7 @@ 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)
             {
@@ -30,11 +32,17 @@ 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) =>
+
+            MqttNetTrace.TraceMessagePublished += (s, e) =>
             {
                 Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
                 if (e.Exception != null)
@@ -45,15 +53,20 @@ namespace MQTTnet.TestApp.NetFramework
 
             try
             {
-                var options = new MqttClientOptions
+                var options = new MqttClientWebSocketOptions
                 {
-                    Server = "localhost",
-                    ClientId = "XYZ",
-                    CleanSession = true
+                    Uri = "broker.hivemq.com:8000/mqtt"
                 };
 
-                var client = new MqttClientFactory().CreateMqttClient(options);
-                client.ApplicationMessageReceived += (s, e) =>
+                ////var options = new MqttClientOptions
+                ////{
+                ////    Server = "localhost",
+                ////    ClientId = "XYZ",
+                ////    CleanSession = true
+                ////};
+
+                var mqttClient = new MqttClientFactory().CreateMqttClient();
+                mqttClient.ApplicationMessageReceived += (s, e) =>
                 {
                     Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
                     Console.WriteLine($"+ Topic = {e.ApplicationMessage.Topic}");
@@ -63,26 +76,24 @@ namespace MQTTnet.TestApp.NetFramework
                     Console.WriteLine();
                 };
 
-                client.Connected += async (s, e) =>
+                mqttClient.Connected += async (s, e) =>
                 {
                     Console.WriteLine("### CONNECTED WITH SERVER ###");
 
-                    await client.SubscribeAsync(new List<TopicFilter>
+                    await mqttClient.SubscribeAsync(new List<TopicFilter>
                     {
                         new TopicFilter("#", MqttQualityOfServiceLevel.AtMostOnce)
                     });
-
-                    Console.WriteLine("### SUBSCRIBED ###");
                 };
 
-                client.Disconnected += async (s, e) =>
+                mqttClient.Disconnected += async (s, e) =>
                 {
                     Console.WriteLine("### DISCONNECTED FROM SERVER ###");
                     await Task.Delay(TimeSpan.FromSeconds(5));
 
                     try
                     {
-                        await client.ConnectAsync();
+                        await mqttClient.ConnectAsync(options);
                     }
                     catch
                     {
@@ -92,7 +103,7 @@ namespace MQTTnet.TestApp.NetFramework
 
                 try
                 {
-                    await client.ConnectAsync();
+                    await mqttClient.ConnectAsync(options);
                 }
                 catch (Exception exception)
                 {
@@ -101,18 +112,13 @@ 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
-                    );
-
-                    await client.PublishAsync(applicationMessage);
+                    var applicationMessage = messageFactory.CreateApplicationMessage("myTopic", "Hello World", MqttQualityOfServiceLevel.AtLeastOnce);
+                    await mqttClient.PublishAsync(applicationMessage);
                 }
             }
             catch (Exception exception)
@@ -121,9 +127,9 @@ namespace MQTTnet.TestApp.NetFramework
             }
         }
 
-        private static void RunServerAsync(string[] arguments)
+        private static async Task RunServerAsync(string[] arguments)
         {
-            MqttTrace.TraceMessagePublished += (s, e) =>
+            MqttNetTrace.TraceMessagePublished += (s, e) =>
             {
                 Console.WriteLine($">> [{e.ThreadId}] [{e.Source}] [{e.Level}]: {e.Message}");
                 if (e.Exception != null)
@@ -151,12 +157,12 @@ namespace MQTTnet.TestApp.NetFramework
                 };
 
                 var mqttServer = new MqttServerFactory().CreateMqttServer(options);
-                mqttServer.Start();
+                await mqttServer.StartAsync();
 
                 Console.WriteLine("Press any key to exit.");
                 Console.ReadLine();
 
-                mqttServer.Stop();
+                await mqttServer.StopAsync();
             }
             catch (Exception e)
             {
@@ -165,5 +171,19 @@ namespace MQTTnet.TestApp.NetFramework
 
             Console.ReadLine();
         }
+
+        private static async Task WikiCode()
+        {
+            // For .NET Framwork & netstandard apps:
+            MqttTcpChannel.CustomCertificateValidationCallback = (x509Certificate, x509Chain, sslPolicyErrors, mqttClientTcpOptions) =>
+            {
+                if (mqttClientTcpOptions.Server == "server_with_revoked_cert")
+                {
+                    return true;
+                }
+
+                return false;
+            };
+        }
     }
-}
+}

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>