Merge branch 'develop' of https://github.com/chkr1011/MQTTnet into develop

# Conflicts:
#	MQTTnet.Core/Serializer/MqttPacketReader.cs
#	MQTTnet.Core/Serializer/MqttPacketSerializer.cs
#	Tests/MQTTnet.TestApp.NetFramework/PerformanceTest.cs

Build/MQTTnet.nuspec

@@ -11,7 +11,7 @@
     <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>* [Client] Added support for web socket communication channel (thanks to nowakpiotr)
-* [Core] Performance optimizations (thanks to JanEggers)
+* [Core] Huge performance optimizations (thanks to JanEggers)
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2017</copyright>
     <tags>MQTT MQTTClient MQTTServer MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Queue Hardware Arduino</tags> 

Frameworks/MQTTnet.NetFramework/Implementations/MqttServerAdapter.cs

@@ -10,7 +10,6 @@ using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Diagnostics;
 using MQTTnet.Core.Serializer;
 using MQTTnet.Core.Server;
-using MQTTnet.Core.Channel;
 
 namespace MQTTnet.Implementations
 {
@@ -87,7 +86,9 @@ namespace MQTTnet.Implementations
                 try
                 {
                     var clientSocket = await Task.Factory.FromAsync(_defaultEndpointSocket.BeginAccept, _defaultEndpointSocket.EndAccept, null).ConfigureAwait(false);
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new BufferedCommunicationChannel(new MqttTcpChannel(clientSocket, null)), new MqttPacketSerializer());
+
+                    var tcpChannel = new MqttTcpChannel(clientSocket, null);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(tcpChannel, new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception) when (!(exception is ObjectDisposedException))
@@ -110,8 +111,9 @@ namespace MQTTnet.Implementations
 
                     var sslStream = new SslStream(new NetworkStream(clientSocket));
                     await sslStream.AuthenticateAsServerAsync(_tlsCertificate, false, SslProtocols.Tls12, false).ConfigureAwait(false);
-                    
+
-                    var clientAdapter = new MqttChannelCommunicationAdapter(new MqttTcpChannel(clientSocket, sslStream), new MqttPacketSerializer());
+                    var tcpChannel = new MqttTcpChannel(clientSocket, sslStream);
+                    var clientAdapter = new MqttChannelCommunicationAdapter(tcpChannel, new MqttPacketSerializer());
                     ClientConnected?.Invoke(this, new MqttClientConnectedEventArgs(clientSocket.RemoteEndPoint.ToString(), clientAdapter));
                 }
                 catch (Exception exception)

Frameworks/MQTTnet.NetFramework/Implementations/MqttTcpChannel.cs

@@ -13,16 +13,19 @@ namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
-        private Stream _dataStream;
         private Socket _socket;
         private SslStream _sslStream;
 
+        public Stream RawStream { get; private set; }
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+
         /// <summary>
         /// called on client sockets are created in connect
         /// </summary>
         public MqttTcpChannel()
         {
-            
+
         }
 
         /// <summary>
@@ -33,7 +36,7 @@ namespace MQTTnet.Implementations
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
             _sslStream = sslStream;
-            _dataStream = (Stream)sslStream ?? new NetworkStream(socket);
+            CreateCommStreams(socket, sslStream);
         }
 
         public async Task ConnectAsync(MqttClientOptions options)
@@ -51,14 +54,11 @@ namespace MQTTnet.Implementations
                 if (options.TlsOptions.UseTls)
                 {
                     _sslStream = new SslStream(new NetworkStream(_socket, true));
-                    
+
-                    _dataStream = _sslStream;
                     await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation).ConfigureAwait(false);
                 }
-                else
+
-                {
+                CreateCommStreams(_socket, _sslStream);
-                    _dataStream = new NetworkStream(_socket);
-                }
             }
             catch (SocketException exception)
             {
@@ -79,45 +79,6 @@ namespace MQTTnet.Implementations
             }
         }
 
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await _dataStream.WriteAsync(buffer, 0, buffer.Length);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            try
-            {
-                var totalBytes = 0;
-
-                do
-                {
-                    var read = await _dataStream.ReadAsync(buffer, totalBytes, length - totalBytes).ConfigureAwait(false);
-                    if (read == 0)
-                    {
-                        throw new MqttCommunicationException(new SocketException((int)SocketError.Disconnecting));
-                    }
-
-                    totalBytes += read;
-                }
-                while (totalBytes < length);
-                return new ArraySegment<byte>(buffer, 0, length);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
         public void Dispose()
         {
             _socket?.Dispose();
@@ -127,6 +88,16 @@ namespace MQTTnet.Implementations
             _sslStream = null;
         }
 
+        private void CreateCommStreams(Socket socket, SslStream sslStream)
+        {
+            RawStream = (Stream)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(RawStream, BufferConstants.Size);
+            ReceiveStream = new BufferedStream(RawStream, BufferConstants.Size);
+        }
+
         private static X509CertificateCollection LoadCertificates(MqttClientOptions options)
         {
             var certificates = new X509CertificateCollection();
@@ -142,10 +113,5 @@ namespace MQTTnet.Implementations
 
             return certificates;
         }
-
-        public int Peek()
-        {
-            return _socket.Available;
-        }
     }
 }

Frameworks/MQTTnet.NetFramework/Implementations/MqttWebSocketChannel.cs

@@ -2,6 +2,7 @@
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Exceptions;
 using System;
+using System.IO;
 using System.Net.WebSockets;
 using System.Threading;
 using System.Threading.Tasks;
@@ -11,8 +12,11 @@ namespace MQTTnet.Implementations
     public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
     {
         private ClientWebSocket _webSocket = new ClientWebSocket();
-        private int WebSocketBufferSize;
+
-        private int WebSocketBufferOffset;
+        public Stream RawStream { get; private set; }
+
+        public Stream SendStream => RawStream;
+        public Stream ReceiveStream => RawStream;
 
         public async Task ConnectAsync(MqttClientOptions options)
         {
@@ -22,6 +26,8 @@ namespace MQTTnet.Implementations
             {
                 _webSocket = new ClientWebSocket();
                 await _webSocket.ConnectAsync(new Uri(options.Server), CancellationToken.None);
+
+                RawStream = new WebSocketStream(_webSocket);
             }
             catch (WebSocketException exception)
             {
@@ -31,6 +37,7 @@ namespace MQTTnet.Implementations
 
         public Task DisconnectAsync()
         {
+            RawStream = null;
             return _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
         }
 
@@ -38,62 +45,5 @@ namespace MQTTnet.Implementations
         {
             _webSocket?.Dispose();
         }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            await ReadToBufferAsync(length, buffer).ConfigureAwait(false);
-            
-            var result = new ArraySegment<byte>(buffer, WebSocketBufferOffset, length);
-            WebSocketBufferSize -= length;
-            WebSocketBufferOffset += length;
-            
-            return result;
-        }
-
-        private async Task ReadToBufferAsync(int length, byte[] buffer)
-        {
-            if (WebSocketBufferSize > 0)
-            {
-                return;
-            }
-
-            var offset = 0;
-            while (_webSocket.State == WebSocketState.Open && WebSocketBufferSize < length)
-            {
-                WebSocketReceiveResult response;
-                do
-                {
-                    response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, offset, buffer.Length - offset), CancellationToken.None).ConfigureAwait(false);
-                    offset += response.Count;
-                } while (!response.EndOfMessage);
-
-                WebSocketBufferSize = response.Count;
-                if (response.MessageType == WebSocketMessageType.Close)
-                {
-                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
-                }
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) {
-                throw new ArgumentNullException(nameof(buffer));
-            }
-
-            try
-            {
-                await _webSocket.SendAsync(new ArraySegment<byte>(buffer), WebSocketMessageType.Binary, true, CancellationToken.None);
-            }
-            catch (WebSocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public int Peek()
-        {
-            return WebSocketBufferSize;
-        }
     }
 }

Frameworks/MQTTnet.NetFramework/Implementations/WebSocketStream.cs

@@ -0,0 +1,80 @@
+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
+        {
+            get { 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

@@ -101,6 +101,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Implementations\MqttWebSocketChannel.cs" />
+    <Compile Include="Implementations\WebSocketStream.cs" />
     <Compile Include="MqttClientFactory.cs" />
     <Compile Include="MqttServerFactory.cs" />
     <Compile Include="Implementations\MqttServerAdapter.cs" />

Frameworks/MQTTnet.NetFramework/MqttClientFactory.cs

@@ -22,7 +22,7 @@ namespace MQTTnet
             {
                 case MqttConnectionType.Tcp:
                 case MqttConnectionType.Tls:
-                    return new BufferedCommunicationChannel( new MqttTcpChannel() );
+                    return new MqttTcpChannel();
                 case MqttConnectionType.Ws:
                 case MqttConnectionType.Wss:
                     return new MqttWebSocketChannel();

Frameworks/MQTTnet.NetStandard/Implementations/MqttServerAdapter.cs

@@ -27,6 +27,7 @@ namespace MQTTnet.Implementations
         public void Start(MqttServerOptions options)
         {
             if (_isRunning) throw new InvalidOperationException("Server is already started.");
+
             _isRunning = true;
 
             _cancellationTokenSource = new CancellationTokenSource();
@@ -107,7 +108,7 @@ namespace MQTTnet.Implementations
 
                     var sslStream = new SslStream(new NetworkStream(clientSocket));
                     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));
                 }

Frameworks/MQTTnet.NetStandard/Implementations/MqttTcpChannel.cs

@@ -13,9 +13,12 @@ namespace MQTTnet.Implementations
 {
     public sealed class MqttTcpChannel : IMqttCommunicationChannel, IDisposable
     {
-        private Stream _dataStream;
         private Socket _socket;
         private SslStream _sslStream;
+        
+        public Stream ReceiveStream { get; private set; }
+        public Stream RawStream => ReceiveStream;
+        public Stream SendStream => ReceiveStream;
 
         /// <summary>
         /// called on client sockets are created in connect
@@ -32,7 +35,7 @@ namespace MQTTnet.Implementations
         {
             _socket = socket ?? throw new ArgumentNullException(nameof(socket));
             _sslStream = sslStream;
-            _dataStream = (Stream)sslStream ?? new NetworkStream(socket);
+            ReceiveStream = (Stream)sslStream ?? new NetworkStream(socket);
         }
 
         public async Task ConnectAsync(MqttClientOptions options)
@@ -51,12 +54,12 @@ namespace MQTTnet.Implementations
                 if (options.TlsOptions.UseTls)
                 {
                     _sslStream = new SslStream(new NetworkStream(_socket, true));
-                    _dataStream = _sslStream;
+                    ReceiveStream = _sslStream;
                     await _sslStream.AuthenticateAsClientAsync(options.Server, LoadCertificates(options), SslProtocols.Tls12, options.TlsOptions.CheckCertificateRevocation).ConfigureAwait(false);
                 }
                 else
                 {
-                    _dataStream = new NetworkStream(_socket);
+                    ReceiveStream = new NetworkStream(_socket);
                 }
             }
             catch (SocketException exception)
@@ -78,45 +81,6 @@ namespace MQTTnet.Implementations
             }
         }
 
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
-
-            try
-            {
-                await _dataStream.WriteAsync(buffer, 0, buffer.Length);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            try
-            {
-                var totalBytes = 0;
-
-                do
-                {
-                    var read = await _dataStream.ReadAsync(buffer, totalBytes, length - totalBytes).ConfigureAwait(false);
-                    if (read == 0)
-                    {
-                        throw new MqttCommunicationException(new SocketException((int)SocketError.Disconnecting));
-                    }
-
-                    totalBytes += read;
-                }
-                while (totalBytes < length);
-                return new ArraySegment<byte>(buffer, 0, length);
-            }
-            catch (SocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
         public void Dispose()
         {
             _socket?.Dispose();
@@ -141,10 +105,5 @@ namespace MQTTnet.Implementations
 
             return certificates;
         }
-
-        public int Peek()
-        {
-            return _socket.Available;
-        }
     }
 }

Frameworks/MQTTnet.NetStandard/Implementations/MqttWebSocketChannel.cs

@@ -2,6 +2,7 @@
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Exceptions;
 using System;
+using System.IO;
 using System.Net.WebSockets;
 using System.Threading;
 using System.Threading.Tasks;
@@ -11,8 +12,10 @@ namespace MQTTnet.Implementations
     public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
     {
         private ClientWebSocket _webSocket = new ClientWebSocket();
-        private int _bufferSize;
+
-        private int _bufferOffset;
+        public Stream SendStream => RawStream;
+        public Stream ReceiveStream => RawStream;
+        public Stream RawStream { get; private set; }
 
         public async Task ConnectAsync(MqttClientOptions options)
         {
@@ -22,6 +25,8 @@ namespace MQTTnet.Implementations
             {
                 _webSocket = new ClientWebSocket();
                 await _webSocket.ConnectAsync(new Uri(options.Server), CancellationToken.None);
+
+                RawStream = new WebSocketStream(_webSocket);
             }
             catch (WebSocketException exception)
             {
@@ -31,6 +36,7 @@ namespace MQTTnet.Implementations
 
         public Task DisconnectAsync()
         {
+            RawStream = null;
             return _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
         }
 
@@ -38,64 +44,5 @@ namespace MQTTnet.Implementations
         {
             _webSocket?.Dispose();
         }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            await ReadToBufferAsync(length, buffer).ConfigureAwait(false);
-
-            var result = new ArraySegment<byte>(buffer, _bufferOffset, length);
-            _bufferSize -= length;
-            _bufferOffset += length;
-
-            return result;
-        }
-
-        private async Task ReadToBufferAsync(int length, byte[] buffer)
-        {
-            if (_bufferSize > 0)
-            {
-                return;
-            }
-
-            var offset = 0;
-            while (_webSocket.State == WebSocketState.Open && _bufferSize < length)
-            {
-                WebSocketReceiveResult response;
-                do
-                {
-                    response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, offset, buffer.Length - offset), CancellationToken.None).ConfigureAwait(false);
-                    offset += response.Count;
-                } while (!response.EndOfMessage);
-
-                _bufferSize = response.Count;
-
-                if (response.MessageType == WebSocketMessageType.Close)
-                {
-                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
-                }
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null)
-            {
-                throw new ArgumentNullException(nameof(buffer));
-            }
-
-            try
-            {
-                await _webSocket.SendAsync(new ArraySegment<byte>(buffer), WebSocketMessageType.Binary, true, CancellationToken.None);
-            }
-            catch (WebSocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public int Peek()
-        {
-            return _bufferSize;
-        }
     }
 }

Frameworks/MQTTnet.NetStandard/Implementations/WebSocketStream.cs

@@ -0,0 +1,80 @@
+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
+        {
+            get { 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.NetStandard/MqttClientFactory.cs

@@ -11,9 +11,7 @@ namespace MQTTnet
     {
         public IMqttClient CreateMqttClient(MqttClientOptions options)
         {
-            if (options == null) {
+            if (options == null) throw new ArgumentNullException(nameof(options));
-                throw new ArgumentNullException(nameof(options));
-            }
 
             return new MqttClient(options, new MqttChannelCommunicationAdapter(GetMqttCommunicationChannel(options), new MqttPacketSerializer()));
         }

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttServerAdapter.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Implementations
     public class MqttServerAdapter : IMqttServerAdapter, IDisposable
     {
         private StreamSocketListener _defaultEndpointSocket;
-        
+
         private bool _isRunning;
 
         public event EventHandler<MqttClientConnectedEventArgs> ClientConnected;
@@ -20,13 +20,14 @@ namespace MQTTnet.Implementations
             if (options == null) throw new ArgumentNullException(nameof(options));
 
             if (_isRunning) throw new InvalidOperationException("Server is already started.");
+
             _isRunning = true;
 
             if (options.DefaultEndpointOptions.IsEnabled)
             {
                 _defaultEndpointSocket = new StreamSocketListener();
                 _defaultEndpointSocket.BindServiceNameAsync(options.GetDefaultEndpointPort().ToString(), SocketProtectionLevel.PlainSocket).GetAwaiter().GetResult();
-                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;                
+                _defaultEndpointSocket.ConnectionReceived += AcceptDefaultEndpointConnectionsAsync;
             }
 
             if (options.TlsEndpointOptions.IsEnabled)

Frameworks/MQTTnet.UniversalWindows/Implementations/MqttWebSocketChannel.cs

@@ -2,6 +2,7 @@
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Exceptions;
 using System;
+using System.IO;
 using System.Net.WebSockets;
 using System.Threading;
 using System.Threading.Tasks;
@@ -11,8 +12,11 @@ namespace MQTTnet.Implementations
     public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
     {
         private ClientWebSocket _webSocket = new ClientWebSocket();
-        private int _bufferSize;
+
-        private int _bufferOffset;
+        public Stream RawStream { get; private set; }
+
+        public Stream SendStream => RawStream;
+        public Stream ReceiveStream => RawStream;
 
         public async Task ConnectAsync(MqttClientOptions options)
         {
@@ -22,6 +26,8 @@ namespace MQTTnet.Implementations
             {
                 _webSocket = new ClientWebSocket();
                 await _webSocket.ConnectAsync(new Uri(options.Server), CancellationToken.None);
+
+                RawStream = new WebSocketStream(_webSocket);
             }
             catch (WebSocketException exception)
             {
@@ -31,6 +37,7 @@ namespace MQTTnet.Implementations
 
         public Task DisconnectAsync()
         {
+            RawStream = null;
             return _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
         }
 
@@ -38,64 +45,5 @@ namespace MQTTnet.Implementations
         {
             _webSocket?.Dispose();
         }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            await ReadToBufferAsync(length, buffer).ConfigureAwait(false);
-
-            var result = new ArraySegment<byte>(buffer, _bufferOffset, length);
-            _bufferSize -= length;
-            _bufferOffset += length;
-
-            return result;
-        }
-
-        private async Task ReadToBufferAsync(int length, byte[] buffer)
-        {
-            if (_bufferSize > 0)
-            {
-                return;
-            }
-
-            var offset = 0;
-            while (_webSocket.State == WebSocketState.Open && _bufferSize < length)
-            {
-                WebSocketReceiveResult response;
-                do
-                {
-                    response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(buffer, offset, buffer.Length - offset), CancellationToken.None).ConfigureAwait(false);
-                    offset += response.Count;
-                } while (!response.EndOfMessage);
-
-                _bufferSize = response.Count;
-
-                if (response.MessageType == WebSocketMessageType.Close)
-                {
-                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
-                }
-            }
-        }
-
-        public async Task WriteAsync(byte[] buffer)
-        {
-            if (buffer == null)
-            {
-                throw new ArgumentNullException(nameof(buffer));
-            }
-
-            try
-            {
-                await _webSocket.SendAsync(new ArraySegment<byte>(buffer), WebSocketMessageType.Binary, true, CancellationToken.None);
-            }
-            catch (WebSocketException exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-
-        public int Peek()
-        {
-            return _bufferSize;
-        }
     }
 }

Frameworks/MQTTnet.UniversalWindows/Implementations/WebSocketStream.cs

@@ -0,0 +1,80 @@
+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
+        {
+            get { 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

@@ -116,6 +116,7 @@
     <Compile Include="MqttServerFactory.cs" />
     <Compile Include="Implementations\MqttTcpChannel.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Implementations\WebSocketStream.cs" />
     <EmbeddedResource Include="Properties\MQTTnet.Universal.rd.xml" />
   </ItemGroup>
   <ItemGroup>

MQTTnet.Core/Adapter/IMqttCommunicationAdapter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using MQTTnet.Core.Client;
 using MQTTnet.Core.Packets;
@@ -12,7 +13,7 @@ namespace MQTTnet.Core.Adapter
 
         Task DisconnectAsync();
 
-        Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout);
+        Task SendPacketsAsync(TimeSpan timeout, IEnumerable<MqttBasePacket> packets);
 
         Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout);
 

MQTTnet.Core/Adapter/MqttChannelCommunicationAdapter.cs

@@ -1,9 +1,12 @@
 using System;
+using System.Collections.Generic;
+using System.IO;
 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 +15,9 @@ namespace MQTTnet.Core.Adapter
     public class MqttChannelCommunicationAdapter : IMqttCommunicationAdapter
     {
         private readonly IMqttCommunicationChannel _channel;
+        private readonly byte[] _readBuffer = new byte[BufferConstants.Size];
+
+        private Task _sendTask = Task.FromResult(0); // this task is used to prevent overlapping write
 
         public MqttChannelCommunicationAdapter(IMqttCommunicationChannel channel, IMqttPacketSerializer serializer)
         {
@@ -23,7 +29,7 @@ namespace MQTTnet.Core.Adapter
 
         public Task ConnectAsync(MqttClientOptions options, TimeSpan timeout)
         {
-            return ExecuteWithTimeoutAsync(_channel.ConnectAsync(options), timeout);
+            return _channel.ConnectAsync(options).TimeoutAfter(timeout);
         }
 
         public Task DisconnectAsync()
@@ -31,25 +37,38 @@ namespace MQTTnet.Core.Adapter
             return _channel.DisconnectAsync();
         }
 
-        public Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
+        public async Task SendPacketsAsync(TimeSpan timeout, IEnumerable<MqttBasePacket> packets)
         {
-            MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), "TX >>> {0} [Timeout={1}]", packet, timeout);
+            lock (_channel)
+            {
+                foreach (var packet in packets)
+                {
+                    MqttTrace.Information(nameof(MqttChannelCommunicationAdapter), "TX >>> {0} [Timeout={1}]", packet, timeout);
 
-            return ExecuteWithTimeoutAsync(PacketSerializer.SerializeAsync(packet, _channel), timeout);
+                    var writeBuffer = PacketSerializer.Serialize(packet);
+
+                    _sendTask = _sendTask.ContinueWith(p => _channel.SendStream.WriteAsync(writeBuffer, 0, writeBuffer.Length));
+                }
+            }
+
+            await _sendTask; // configure await false geneates stackoverflow
+            await _channel.SendStream.FlushAsync().TimeoutAfter(timeout).ConfigureAwait(false);
         }
 
         public async Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout)
         {
-            MqttBasePacket packet;
+            Tuple<MqttPacketHeader, MemoryStream> tuple;
             if (timeout > TimeSpan.Zero)
             {
-                packet = await ExecuteWithTimeoutAsync(PacketSerializer.DeserializeAsync(_channel), timeout).ConfigureAwait(false);
+                tuple = await ReceiveAsync(_channel.RawStream).TimeoutAfter(timeout).ConfigureAwait(false);
             }
             else
             {
-                packet = await PacketSerializer.DeserializeAsync(_channel).ConfigureAwait(false);
+                tuple = await ReceiveAsync(_channel.ReceiveStream).ConfigureAwait(false);
             }
 
+            var packet = PacketSerializer.Deserialize(tuple.Item1, tuple.Item2);
+
             if (packet == null)
             {
                 throw new MqttProtocolViolationException("Received malformed packet.");
@@ -59,34 +78,27 @@ namespace MQTTnet.Core.Adapter
             return packet;
         }
 
-        private static async Task<TResult> ExecuteWithTimeoutAsync<TResult>(Task<TResult> task, TimeSpan timeout)
+        private async Task<Tuple<MqttPacketHeader, MemoryStream>> ReceiveAsync(Stream stream)
         {
-            var timeoutTask = Task.Delay(timeout);
+            var header = MqttPacketReader.ReadHeaderFromSource(stream);
-            if (await Task.WhenAny(timeoutTask, task).ConfigureAwait(false) == timeoutTask)
+
+            MemoryStream body;
+            if (header.BodyLength > 0)
             {
-                throw new MqttCommunicationTimedOutException();
+                var totalRead = 0;
+                do
+                {
+                    var read = await stream.ReadAsync(_readBuffer, totalRead, header.BodyLength - totalRead).ConfigureAwait(false);
+                    totalRead += read;
+                } while (totalRead < header.BodyLength);
+                body = new MemoryStream(_readBuffer, 0, header.BodyLength);
+            }
+            else
+            {
+                body = new MemoryStream();
             }
 
-            if (task.IsFaulted)
+            return Tuple.Create(header, body);
-            {
-                throw new MqttCommunicationException(task.Exception);
-            }
-
-            return task.Result;
-        }
-
-        private static async Task ExecuteWithTimeoutAsync(Task task, TimeSpan timeout)
-        {
-            var timeoutTask = Task.Delay(timeout);
-            if (await Task.WhenAny(timeoutTask, task).ConfigureAwait(false) == timeoutTask)
-            {
-                throw new MqttCommunicationTimedOutException();
-            }
-
-            if (task.IsFaulted)
-            {
-                throw new MqttCommunicationException(task.Exception);
-            }
         }
     }
 }

MQTTnet.Core/Adapter/MqttCommunicationAdapterExtensions.cs

@@ -0,0 +1,14 @@
+using System;
+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, params MqttBasePacket[] packets)
+        {
+            return adapter.SendPacketsAsync(timeout, 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/Channel/BufferedCommunicationChannel.cs

@@ -1,77 +0,0 @@
-using System.Threading.Tasks;
-using MQTTnet.Core.Client;
-using System;
-
-namespace MQTTnet.Core.Channel
-{
-    public class BufferedCommunicationChannel : IMqttCommunicationChannel
-    {
-        private readonly IMqttCommunicationChannel _inner;
-        private int _bufferSize;
-        private int _bufferOffset;
-
-        public BufferedCommunicationChannel(IMqttCommunicationChannel inner)
-        {
-            _inner = inner;
-        }
-
-        public Task ConnectAsync(MqttClientOptions options)
-        {
-            return _inner.ConnectAsync(options);
-        }
-
-        public Task DisconnectAsync()
-        {
-            return _inner.DisconnectAsync();
-        }
-
-        public int Peek()
-        {
-            return _inner.Peek();
-        }
-
-        public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-        {
-            //read from buffer
-            if (_bufferSize > 0)
-            {
-                return ReadFomBuffer(length, buffer);
-            }
-
-            var available = _inner.Peek();
-            // if there are less or equal bytes available then requested then just read em
-            if (available <= length)
-            {
-                return await _inner.ReadAsync(length, buffer);
-            }
-
-            //if more bytes are available than requested do buffer them to reduce calls to network buffers
-            await WriteToBuffer(available, buffer).ConfigureAwait(false);
-            return ReadFomBuffer(length, buffer);
-        }
-
-        private async Task WriteToBuffer(int available, byte[] buffer)
-        {
-            await _inner.ReadAsync(available, buffer).ConfigureAwait(false);
-            _bufferSize = available;
-            _bufferOffset = 0;
-        }
-
-        private ArraySegment<byte> ReadFomBuffer(int length, byte[] buffer)
-        {
-            var result = new ArraySegment<byte>(buffer, _bufferOffset, length);
-            _bufferSize -= length;
-            _bufferOffset += length;
-
-            if (_bufferSize < 0)
-            {
-            }
-            return result;
-        }
-
-        public Task WriteAsync(byte[] buffer)
-        {
-            return _inner.WriteAsync(buffer);
-        }
-    }
-}

MQTTnet.Core/Channel/IMqttCommunicationChannel.cs

@@ -1,6 +1,6 @@
 using System.Threading.Tasks;
 using MQTTnet.Core.Client;
-using System;
+using System.IO;
 
 namespace MQTTnet.Core.Channel
 {
@@ -9,14 +9,11 @@ namespace MQTTnet.Core.Channel
         Task ConnectAsync(MqttClientOptions options);
 
         Task DisconnectAsync();
+        
+        Stream SendStream { get; }
 
-        Task WriteAsync(byte[] buffer);
+        Stream ReceiveStream { get; }
 
-        /// <summary>
+        Stream RawStream { get; }
-        /// get the currently available number of bytes without reading them
-        /// </summary>
-        int Peek();
-
-        Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer);
     }
 }

MQTTnet.Core/Client/IMqttClient.cs

@@ -15,7 +15,7 @@ namespace MQTTnet.Core.Client
 
         Task ConnectAsync(MqttApplicationMessage willApplicationMessage = null);
         Task DisconnectAsync();
-        Task PublishAsync(MqttApplicationMessage applicationMessage);
+        Task PublishAsync(IEnumerable<MqttApplicationMessage> applicationMessages);
         Task<IList<MqttSubscribeResult>> SubscribeAsync(IList<TopicFilter> topicFilters);
         Task<IList<MqttSubscribeResult>> SubscribeAsync(params TopicFilter[] topicFilters);
         Task Unsubscribe(IList<string> topicFilters);

MQTTnet.Core/Client/MqttClient.cs

@@ -161,32 +161,43 @@ namespace MQTTnet.Core.Client
             return SendAndReceiveAsync<MqttUnsubAckPacket>(unsubscribePacket);
         }
 
-        public 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]
+                var qosPackets = qosGroup.ToArray();
-                return SendAsync(publishPacket);
+                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, 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();
+                                await PublishExactlyOncePacketAsync(publishPacket);
+                            }
+                            break;
+                        }
+                    default:
+                        throw new InvalidOperationException();
+                }
             }
-
-            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
-            {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                return SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
-            }
-
-            if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
-            {
-                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                return PublishExactlyOncePacketAsync(publishPacket);
-            }
-
-            throw new InvalidOperationException();
         }
 
         private async Task PublishExactlyOncePacketAsync(MqttBasePacket publishPacket)
@@ -277,12 +288,14 @@ namespace MQTTnet.Core.Client
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtMostOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
                 await SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
@@ -295,6 +308,7 @@ namespace MQTTnet.Core.Client
 
                 FireApplicationMessageReceivedEvent(publishPacket);
                 await SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                return;
             }
 
             throw new MqttCommunicationException("Received a not supported QoS level.");
@@ -312,13 +326,12 @@ namespace MQTTnet.Core.Client
 
         private Task SendAsync(MqttBasePacket packet)
         {
-            return _adapter.SendPacketAsync(packet, _options.DefaultCommunicationTimeout);
+            return _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, packet);
         }
 
         private async Task<TResponsePacket> SendAndReceiveAsync<TResponsePacket>(MqttBasePacket requestPacket) where TResponsePacket : MqttBasePacket
         {
-            await _adapter.SendPacketAsync(requestPacket, _options.DefaultCommunicationTimeout).ConfigureAwait(false);
+            await _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, requestPacket).ConfigureAwait(false);
-
             return (TResponsePacket)await _packetDispatcher.WaitForPacketAsync(requestPacket, typeof(TResponsePacket), _options.DefaultCommunicationTimeout).ConfigureAwait(false);
         }
 

MQTTnet.Core/Client/MqttClientExtensions.cs

@@ -0,0 +1,12 @@
+using System.Threading.Tasks;
+
+namespace MQTTnet.Core.Client
+{
+    public static class MqttClientExtensions
+    {
+        public static Task PublishAsync(this IMqttClient client, params MqttApplicationMessage[] applicationMessages)
+        {
+            return client.PublishAsync(applicationMessages);
+        }
+    }
+}

MQTTnet.Core/Client/MqttPacketDispatcher.cs

@@ -3,6 +3,7 @@ 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;
 
@@ -13,7 +14,7 @@ namespace MQTTnet.Core.Client
         private readonly object _syncRoot = new object();
         private readonly HashSet<MqttBasePacket> _receivedPackets = new HashSet<MqttBasePacket>();
         private readonly ConcurrentDictionary<Type, TaskCompletionSource<MqttBasePacket>> _packetByResponseType = new ConcurrentDictionary<Type, TaskCompletionSource<MqttBasePacket>>();
-        private readonly ConcurrentDictionary<ushort,TaskCompletionSource<MqttBasePacket>> _packetByIdentifier = new ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>();
+        private readonly ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>> _packetByIdentifier = new ConcurrentDictionary<ushort, TaskCompletionSource<MqttBasePacket>>();
 
         public async Task<MqttBasePacket> WaitForPacketAsync(MqttBasePacket request, Type responseType, TimeSpan timeout)
         {
@@ -22,16 +23,19 @@ namespace MQTTnet.Core.Client
             var packetAwaiter = AddPacketAwaiter(request, responseType);
             DispatchPendingPackets();
 
-            var hasTimeout = await Task.WhenAny(Task.Delay(timeout), packetAwaiter.Task).ConfigureAwait(false) != packetAwaiter.Task;
+            try
-            RemovePacketAwaiter(request, responseType);
+            {
-
+                return await packetAwaiter.Task.TimeoutAfter(timeout);
-            if (hasTimeout)
+            }
+            catch (MqttCommunicationTimedOutException)
             {
                 MqttTrace.Warning(nameof(MqttPacketDispatcher), "Timeout while waiting for packet.");
-                throw new MqttCommunicationTimedOutException();
+                throw;
+            }
+            finally
+            {
+                RemovePacketAwaiter(request, responseType);
             }
-
-            return packetAwaiter.Task.Result;
         }
 
         public void Dispatch(MqttBasePacket packet)
@@ -48,9 +52,9 @@ namespace MQTTnet.Core.Client
                     packetDispatched = true;
                 }
             }
-            else if (_packetByResponseType.TryRemove(packet.GetType(), out var tcs) )
+            else if (_packetByResponseType.TryRemove(packet.GetType(), out var tcs))
             {
-                tcs.TrySetResult( packet);
+                tcs.TrySetResult(packet);
                 packetDispatched = true;
             }
 
@@ -96,11 +100,11 @@ namespace MQTTnet.Core.Client
         {
             if (request is IMqttPacketWithIdentifier withIdent)
             {
-                _packetByIdentifier.TryRemove(withIdent.PacketIdentifier, out var tcs);
+                _packetByIdentifier.TryRemove(withIdent.PacketIdentifier, out var _);
             }
             else
             {
-                _packetByResponseType.TryRemove(responseType, out var tcs);
+                _packetByResponseType.TryRemove(responseType, out var _);
             }
         }
 

MQTTnet.Core/Diagnostics/MqttTrace.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Linq;
 
 namespace MQTTnet.Core.Diagnostics
 {

MQTTnet.Core/Diagnostics/MqttTraceLevel.cs

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

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 +1,55 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Exceptions;
+
+namespace MQTTnet.Core.Internal
+{
+    public static class TaskExtensions
+    {
+        public static Task TimeoutAfter(this Task task, TimeSpan timeout)
+        {
+            return TimeoutAfter(task.ContinueWith(t => 0), timeout);
+        }
+
+        public static async Task<TResult> TimeoutAfter<TResult>(this Task<TResult> task, TimeSpan timeout)
+        {
+            using (var cancellationTokenSource = new CancellationTokenSource())
+            {
+                var tcs = new TaskCompletionSource<TResult>();
+
+                cancellationTokenSource.Token.Register(() =>
+                {
+                    tcs.TrySetCanceled();
+                });
+
+                try
+                {
+                    cancellationTokenSource.CancelAfter(timeout);
+                    task.ContinueWith(t =>
+                   {
+                       if (t.IsFaulted)
+                       {
+                           tcs.TrySetException(t.Exception);
+                       }
+
+                       if (t.IsCompleted)
+                       {
+                           tcs.TrySetResult(t.Result);
+                       }
+                   }, cancellationTokenSource.Token);
+
+                    return await tcs.Task;
+                }
+                catch (TaskCanceledException)
+                {
+                    throw new MqttCommunicationTimedOutException();
+                }
+                catch (Exception e)
+                {
+                    throw new MqttCommunicationException(e);
+                }
+            }
+        }
+    }
+}

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>

MQTTnet.Core/Packets/MqttPublishPacket.cs

@@ -17,7 +17,7 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return nameof(MqttPublishPacket) + 
+            return nameof(MqttPublishPacket) +
                 ": [Topic=" + Topic + "]" +
                 " [Payload=" + Convert.ToBase64String(Payload) + "]" +
                 " [QoSLevel=" + QualityOfServiceLevel + "]" +

MQTTnet.Core/Packets/MqttSubscribePacket.cs

@@ -6,7 +6,7 @@ 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()

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 System.IO;
-using MQTTnet.Core.Channel;
 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(MqttPacketHeader header, MemoryStream stream);
     }
 }

MQTTnet.Core/Serializer/MqttPacketReader.cs

@@ -1,10 +1,8 @@
 using System;
 using System.IO;
 using System.Text;
-using System.Threading.Tasks;
 using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Protocol;
-using MQTTnet.Core.Channel;
 using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Serializer
@@ -13,14 +11,14 @@ namespace MQTTnet.Core.Serializer
     {
         private readonly MqttPacketHeader _header;
 
-        public MqttPacketReader(MqttPacketHeader header, Stream body)
+        public MqttPacketReader(Stream stream, MqttPacketHeader header)
-            : base(body)
+            : base(stream, Encoding.UTF8, true)
         {
             _header = header;
         }
-        
+
         public bool EndOfRemainingData => BaseStream.Position == _header.BodyLength;
-        
+
         public override ushort ReadUInt16()
         {
             var buffer = ReadBytes(2);
@@ -49,14 +47,11 @@ namespace MQTTnet.Core.Serializer
             return ReadBytes(_header.BodyLength - (int)BaseStream.Position);
         }
 
-        public static async Task<MqttPacketHeader> ReadHeaderFromSourceAsync(IMqttCommunicationChannel source, byte[] buffer)
+        public static MqttPacketHeader ReadHeaderFromSource(Stream stream)
         {
-            var fixedHeader = await ReadStreamByteAsync(source, buffer).ConfigureAwait(false);
+            var fixedHeader = (byte)stream.ReadByte();
-            var byteReader = new ByteReader(fixedHeader);
+            var controlPacketType = (MqttControlPacketType)(fixedHeader >> 4);
-            byteReader.Read(4);
+            var bodyLength = ReadBodyLengthFromSource(stream);
-
-            var controlPacketType = (MqttControlPacketType)byteReader.Read(4);
-            var bodyLength = await ReadBodyLengthFromSourceAsync(source, buffer).ConfigureAwait(false);
 
             return new MqttPacketHeader
             {
@@ -66,25 +61,7 @@ namespace MQTTnet.Core.Serializer
             };
         }
 
-        private static async Task<byte> ReadStreamByteAsync(IMqttCommunicationChannel source, byte[] readBuffer)
+        private static int ReadBodyLengthFromSource(Stream stream)
-        {
-            var result = await ReadFromSourceAsync(source, 1, readBuffer).ConfigureAwait(false);
-            return result.Array[result.Offset];
-        }
-
-        public static async Task<ArraySegment<byte>> ReadFromSourceAsync(IMqttCommunicationChannel source, int length, byte[] buffer)
-        {
-            try
-            {
-                return await source.ReadAsync(length, buffer);
-            }
-            catch (Exception exception)
-            {
-                throw new MqttCommunicationException(exception);
-            }
-        }
-        
-        private static async Task<int> ReadBodyLengthFromSourceAsync(IMqttCommunicationChannel source, byte[] buffer)
         {
             // Alorithm taken from http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html.
             var multiplier = 1;
@@ -92,7 +69,7 @@ namespace MQTTnet.Core.Serializer
             byte encodedByte;
             do
             {
-                encodedByte = await ReadStreamByteAsync(source, buffer).ConfigureAwait(false);
+                encodedByte = (byte)stream.ReadByte();
                 value += (encodedByte & 127) * multiplier;
                 multiplier *= 128;
                 if (multiplier > 128 * 128 * 128)

MQTTnet.Core/Serializer/MqttPacketSerializer.cs

@@ -3,8 +3,6 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Text;
-using System.Threading.Tasks;
-using MQTTnet.Core.Channel;
 using MQTTnet.Core.Exceptions;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
@@ -17,12 +15,10 @@ namespace MQTTnet.Core.Serializer
         private static byte[] ProtocolVersionV310Name { get; } = Encoding.UTF8.GetBytes("MQIs");
 
         public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
-        private byte[] _readBuffer = new byte[BufferConstants.Size];  // TODO: What happens if the message is bigger?
 
-        public async 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))
@@ -30,9 +26,12 @@ namespace MQTTnet.Core.Serializer
                 var header = new List<byte> { SerializePacket(packet, writer) };
                 var body = stream.ToArray();
                 MqttPacketWriter.BuildLengthHeader(body.Length, header);
-                
+                var headerArray = header.ToArray();
-                await destination.WriteAsync(header.ToArray()).ConfigureAwait(false);
+                var writeBuffer = new byte[header.Count + body.Length];
-                await destination.WriteAsync(body).ConfigureAwait(false);
+                Buffer.BlockCopy(headerArray, 0, writeBuffer, 0, headerArray.Length);
+                Buffer.BlockCopy(body, 0, writeBuffer, headerArray.Length, body.Length);
+
+                return writeBuffer;
             }
         }
 
@@ -111,119 +110,112 @@ namespace MQTTnet.Core.Serializer
             throw new MqttProtocolViolationException("Packet type invalid.");
         }
 
-        public async Task<MqttBasePacket> DeserializeAsync(IMqttCommunicationChannel source)
+        public MqttBasePacket Deserialize(MqttPacketHeader header, MemoryStream body)
         {
-            if (source == null) throw new ArgumentNullException(nameof(source));
+            if (header == null) throw new ArgumentNullException(nameof(header));
+            if (body == null) throw new ArgumentNullException(nameof(body));
 
-            var header = await MqttPacketReader.ReadHeaderFromSourceAsync(source, _readBuffer).ConfigureAwait(false);
+            using (var reader = new MqttPacketReader(body, header))
-            var body = await GetBody(source, header).ConfigureAwait(false);
-
-            using (var mqttPacketReader = new MqttPacketReader(header, body))
             {
-                switch (header.ControlPacketType)
+                return Deserialize(header, reader);
-                {
-                    case MqttControlPacketType.Connect:
-                        {
-                            return DeserializeConnect(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.ConnAck:
-                        {
-                            return DeserializeConnAck(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.Disconnect:
-                        {
-                            return new MqttDisconnectPacket();
-                        }
-
-                    case MqttControlPacketType.Publish:
-                        {
-                            return DeserializePublish(mqttPacketReader, header);
-                        }
-
-                    case MqttControlPacketType.PubAck:
-                        {
-                            return new MqttPubAckPacket
-                            {
-                                PacketIdentifier = mqttPacketReader.ReadUInt16()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubRec:
-                        {
-                            return new MqttPubRecPacket
-                            {
-                                PacketIdentifier = mqttPacketReader.ReadUInt16()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubRel:
-                        {
-                            return new MqttPubRelPacket
-                            {
-                                PacketIdentifier = mqttPacketReader.ReadUInt16()
-                            };
-                        }
-
-                    case MqttControlPacketType.PubComp:
-                        {
-                            return new MqttPubCompPacket
-                            {
-                                PacketIdentifier = mqttPacketReader.ReadUInt16()
-                            };
-                        }
-
-                    case MqttControlPacketType.PingReq:
-                        {
-                            return new MqttPingReqPacket();
-                        }
-
-                    case MqttControlPacketType.PingResp:
-                        {
-                            return new MqttPingRespPacket();
-                        }
-
-                    case MqttControlPacketType.Subscribe:
-                        {
-                            return DeserializeSubscribe(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.SubAck:
-                        {
-                            return DeserializeSubAck(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.Unsubscibe:
-                        {
-                            return DeserializeUnsubscribe(mqttPacketReader);
-                        }
-
-                    case MqttControlPacketType.UnsubAck:
-                        {
-                            return new MqttUnsubAckPacket
-                            {
-                                PacketIdentifier = mqttPacketReader.ReadUInt16()
-                            };
-                        }
-
-                    default:
-                        {
-                            throw new MqttProtocolViolationException($"Packet type ({(int)header.ControlPacketType}) not supported.");
-                        }
-                }
             }
         }
 
-        private async Task<MemoryStream> GetBody(IMqttCommunicationChannel source, MqttPacketHeader header)
+        private static MqttBasePacket Deserialize(MqttPacketHeader header, MqttPacketReader reader)
         {
-            if (header.BodyLength > 0)
+            switch (header.ControlPacketType)
             {
-                var segment = await MqttPacketReader.ReadFromSourceAsync(source, header.BodyLength, _readBuffer).ConfigureAwait(false);
+                case MqttControlPacketType.Connect:
-                return new MemoryStream(segment.Array, segment.Offset, segment.Count);
+                    {
+                        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.");
+                    }
             }
-           
-            return new MemoryStream();
         }
 
         private static MqttBasePacket DeserializeUnsubscribe(MqttPacketReader reader)
@@ -514,12 +506,21 @@ namespace MQTTnet.Core.Serializer
                 writer.Write(packet.Payload);
             }
 
-            var fixedHeader = new ByteWriter();
+            byte fixedHeader = 0;
-            fixedHeader.Write(packet.Retain);
-            fixedHeader.Write((byte)packet.QualityOfServiceLevel, 2);
-            fixedHeader.Write(packet.Dup);
 
-            return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.Publish, fixedHeader.Value);
+            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)

MQTTnet.Core/Serializer/MqttPacketWriter.cs

@@ -8,10 +8,9 @@ namespace MQTTnet.Core.Serializer
 {
     public sealed class MqttPacketWriter : BinaryWriter
     {
-        public MqttPacketWriter( Stream stream )
+        public MqttPacketWriter(Stream stream)
             : base(stream)
         {
-
         }
 
         public static byte BuildFixedHeader(MqttControlPacketType packetType, byte flags = 0)
@@ -20,7 +19,7 @@ namespace MQTTnet.Core.Serializer
             fixedHeader |= flags;
             return (byte)fixedHeader;
         }
-        
+
         public override void Write(ushort value)
         {
             var buffer = BitConverter.GetBytes(value);
@@ -43,7 +42,7 @@ namespace MQTTnet.Core.Serializer
 
             Write(value.Value);
         }
-        
+
         public void WriteWithLengthPrefix(string value)
         {
             WriteWithLengthPrefix(Encoding.UTF8.GetBytes(value ?? string.Empty));

MQTTnet.Core/Server/MqttClientMessageQueue.cs

@@ -1,20 +1,17 @@
 using System;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
-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 BlockingCollection<MqttClientPublishPacketContext> _pendingPublishPackets = new BlockingCollection<MqttClientPublishPacketContext>();
-        private readonly AsyncGate _gate = new AsyncGate();
 
         private readonly MqttServerOptions _options;
         private CancellationTokenSource _cancellationTokenSource;
@@ -43,26 +40,22 @@ namespace MQTTnet.Core.Server
             _adapter = null;
             _cancellationTokenSource?.Cancel();
             _cancellationTokenSource = null;
+            _pendingPublishPackets?.Dispose();
         }
 
         public void Enqueue(MqttPublishPacket publishPacket)
         {
             if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
 
-            lock (_pendingPublishPackets)
+            _pendingPublishPackets.Add(new MqttClientPublishPacketContext(publishPacket));
-            {
-                _pendingPublishPackets.Add(new MqttClientPublishPacketContext(publishPacket));
-                _gate.Set();
-            }
         }
 
         private async Task SendPendingPublishPacketsAsync(CancellationToken cancellationToken)
         {
-            while (!cancellationToken.IsCancellationRequested)
+            foreach (var publishPacket in _pendingPublishPackets.GetConsumingEnumerable(cancellationToken))
             {
                 try
                 {
-                    await _gate.WaitOneAsync().ConfigureAwait(false);
                     if (cancellationToken.IsCancellationRequested)
                     {
                         return;
@@ -73,25 +66,12 @@ namespace MQTTnet.Core.Server
                         continue;
                     }
 
-                    List<MqttClientPublishPacketContext> pendingPublishPackets;
+                    await TrySendPendingPublishPacketAsync(publishPacket).ConfigureAwait(false);
-                    lock (_pendingPublishPackets)
-                    {
-                        pendingPublishPackets = _pendingPublishPackets.ToList();
-                    }
-
-                    foreach (var publishPacket in pendingPublishPackets)
-                    {
-                        await TrySendPendingPublishPacketAsync(publishPacket).ConfigureAwait(false);
-                    }
                 }
                 catch (Exception e)
                 {
                     MqttTrace.Error(nameof(MqttClientMessageQueue), e, "Error while sending pending publish packets.");
                 }
-                finally
-                {
-                    Cleanup();
-                }               
             }
         }
 
@@ -105,30 +85,24 @@ namespace MQTTnet.Core.Server
                 }
 
                 publishPacketContext.PublishPacket.Dup = publishPacketContext.SendTries > 0;
-                await _adapter.SendPacketAsync(publishPacketContext.PublishPacket, _options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                await _adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, publishPacketContext.PublishPacket).ConfigureAwait(false);
 
                 publishPacketContext.IsSent = true;
             }
             catch (MqttCommunicationException exception)
             {
                 MqttTrace.Warning(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
+                _pendingPublishPackets.Add(publishPacketContext);
             }
             catch (Exception exception)
             {
                 MqttTrace.Error(nameof(MqttClientMessageQueue), exception, "Sending publish packet failed.");
+                _pendingPublishPackets.Add(publishPacketContext);
             }
             finally
             {
                 publishPacketContext.SendTries++;
             }
         }
-
-        private void Cleanup()
-        {
-            lock (_pendingPublishPackets)
-            {
-                _pendingPublishPackets.RemoveAll(p => p.IsSent);
-            }
-        }
     }
 }

MQTTnet.Core/Server/MqttClientSession.cs

@@ -103,12 +103,12 @@ namespace MQTTnet.Core.Server
         {
             if (packet is MqttSubscribePacket subscribePacket)
             {
-                return Adapter.SendPacketAsync(_subscriptionsManager.Subscribe(subscribePacket), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _subscriptionsManager.Subscribe(subscribePacket));
             }
 
             if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                return Adapter.SendPacketAsync(_subscriptionsManager.Unsubscribe(unsubscribePacket), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _subscriptionsManager.Unsubscribe(unsubscribePacket));
             }
 
             if (packet is MqttPublishPacket publishPacket)
@@ -123,7 +123,7 @@ namespace MQTTnet.Core.Server
 
             if (packet is MqttPubRecPacket pubRecPacket)
             {
-                return Adapter.SendPacketAsync(pubRecPacket.CreateResponse<MqttPubRelPacket>(), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, pubRecPacket.CreateResponse<MqttPubRelPacket>());
             }
 
             if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
@@ -134,7 +134,7 @@ namespace MQTTnet.Core.Server
 
             if (packet is MqttPingReqPacket)
             {
-                return Adapter.SendPacketAsync(new MqttPingRespPacket(), _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttPingRespPacket());
             }
 
             if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
@@ -160,7 +160,7 @@ namespace MQTTnet.Core.Server
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 _publishPacketReceivedCallback(this, publishPacket);
-                return Adapter.SendPacketAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
             }
 
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.ExactlyOnce)
@@ -173,7 +173,7 @@ namespace MQTTnet.Core.Server
 
                 _publishPacketReceivedCallback(this, publishPacket);
 
-                return Adapter.SendPacketAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+                return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
             }
 
             throw new MqttCommunicationException("Received a not supported QoS level.");
@@ -186,7 +186,7 @@ namespace MQTTnet.Core.Server
                 _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
 
-            return Adapter.SendPacketAsync(new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier }, _options.DefaultCommunicationTimeout);
+            return Adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier });
         }
     }
 }

MQTTnet.Core/Server/MqttClientSessionsManager.cs

@@ -40,21 +40,21 @@ namespace MQTTnet.Core.Server
                 var connectReturnCode = ValidateConnection(connectPacket);
                 if (connectReturnCode != MqttConnectReturnCode.ConnectionAccepted)
                 {
-                    await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                    await eventArgs.ClientAdapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttConnAckPacket
                     {
                         ConnectReturnCode = connectReturnCode
-                    }, _options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                    }).ConfigureAwait(false);
 
                     return;
                 }
 
                 var clientSession = GetOrCreateClientSession(connectPacket);
 
-                await eventArgs.ClientAdapter.SendPacketAsync(new MqttConnAckPacket
+                await eventArgs.ClientAdapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, new MqttConnAckPacket
                 {
                     ConnectReturnCode = connectReturnCode,
                     IsSessionPresent = clientSession.IsExistingSession
-                }, _options.DefaultCommunicationTimeout).ConfigureAwait(false);
+                }).ConfigureAwait(false);
 
                 await clientSession.Session.RunAsync(eventArgs.Identifier, connectPacket.WillMessage, eventArgs.ClientAdapter).ConfigureAwait(false);
             }

MQTTnet.Core/Server/MqttServer.cs

@@ -20,7 +20,7 @@ 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);
         }
@@ -61,7 +61,7 @@ namespace MQTTnet.Core.Server
                 adapter.ClientConnected += OnClientConnected;
                 adapter.Start(_options);
             }
-            
+
             MqttTrace.Information(nameof(MqttServer), "Started.");
         }
 

MQTTnet.Core/Server/MqttServerOptions.cs

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

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

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
+    <DebugType>Full</DebugType>
     <TargetFramework>netcoreapp2.0</TargetFramework>
   </PropertyGroup>
 

README.md

@@ -10,13 +10,14 @@ MQTTnet is a .NET library for MQTT based communication. It provides a MQTT clien
 # Features
 
 ## General
+* Performance optimized (publishing ~18.000 messages per second on local machine)
 * Async support
 * TLS 1.2 support for client and server (but not UWP servers)
 * Extensible communication channels (i.e. In-Memory, TCP, TCP+TLS, WS)
 * Interfaces included for mocking and testing
 * Lightweight (only the low level implementation of MQTT, no overhead)
 * Access to internal trace messages
-* Unit tested (50+ tests)
+* Unit tested (55+ tests)
 
 ## Client
 * Rx support (via another project)

Tests/MQTTnet.Core.Tests/ExtensionTests.cs

@@ -0,0 +1,33 @@
+using System;
+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 TestTimeoutAfter()
+        {
+            await Task.Delay(TimeSpan.FromMilliseconds(500)).TimeoutAfter(TimeSpan.FromMilliseconds(100));
+        }
+
+        [ExpectedException(typeof( MqttCommunicationTimedOutException))]
+        [TestMethod]
+        public async Task TestTimeoutAfterWithResult()
+        {
+            await Task.Delay(TimeSpan.FromMilliseconds(500)).ContinueWith(t =>  5).TimeoutAfter(TimeSpan.FromMilliseconds(100));
+        }
+        
+        [TestMethod]
+        public async Task TestTimeoutAfterCompleteInTime()
+        {
+            var result = await Task.Delay( TimeSpan.FromMilliseconds( 100 ) ).ContinueWith( t => 5 ).TimeoutAfter( TimeSpan.FromMilliseconds( 500 ) );
+            Assert.AreEqual( 5, result );
+        }
+    }
+}

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

@@ -86,6 +86,7 @@
   <ItemGroup>
     <Compile Include="ByteReaderTests.cs" />
     <Compile Include="ByteWriterTests.cs" />
+    <Compile Include="ExtensionTests.cs" />
     <Compile Include="MqttPacketSerializerTests.cs" />
     <Compile Include="MqttServerTests.cs" />
     <Compile Include="MqttSubscriptionsManagerTests.cs" />

Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs

@@ -391,6 +391,12 @@ namespace MQTTnet.Core.Tests
         {
             private readonly MemoryStream _stream = new MemoryStream();
 
+            public Stream ReceiveStream => _stream;
+
+            public Stream RawStream => _stream;
+
+            public Stream SendStream => _stream;
+
             public bool IsConnected { get; } = true;
 
             public TestChannel()
@@ -413,34 +419,16 @@ namespace MQTTnet.Core.Tests
                 return Task.FromResult(0);
             }
 
-            public Task WriteAsync(byte[] buffer)
-            {
-                return _stream.WriteAsync(buffer, 0, buffer.Length);
-            }
-
-            public async Task<ArraySegment<byte>> ReadAsync(int length, byte[] buffer)
-            {
-                await _stream.ReadAsync(buffer, 0, length);
-                return new ArraySegment<byte>(buffer, 0, length);
-            }
-
             public byte[] ToArray()
             {
                 return _stream.ToArray();
             }
-
-            public int Peek()
-            {
-                return (int)_stream.Length - (int)_stream.Position;
-            }
         }
 
         private static void SerializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
             var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
-            var channel = new TestChannel();
+            var buffer = serializer.Serialize(packet);
-            serializer.SerializeAsync(packet, channel).Wait();
-            var buffer = channel.ToArray();
 
             Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(buffer));
         }
@@ -448,19 +436,21 @@ namespace MQTTnet.Core.Tests
         private static void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value)
         {
             var serializer = new MqttPacketSerializer();
+            
+            var buffer1 = serializer.Serialize(packet);
 
-            var channel1 = new TestChannel();
+            using (var headerStream = new MemoryStream( buffer1 ))
-            serializer.SerializeAsync(packet, channel1).Wait();
+            {
-            var buffer1 = channel1.ToArray();
+                var header = MqttPacketReader.ReadHeaderFromSource( headerStream );
 
-            var channel2 = new TestChannel(buffer1);
+                using (var bodyStream = new MemoryStream( buffer1, (int)headerStream.Position, header.BodyLength ))
-            var deserializedPacket = serializer.DeserializeAsync(channel2).Result;
+                {
-            var buffer2 = channel2.ToArray();
+                    var deserializedPacket = serializer.Deserialize(header, bodyStream);
+                    var buffer2 = serializer.Serialize( deserializedPacket );
 
-            var channel3 = new TestChannel(buffer2);
+                    Assert.AreEqual( expectedBase64Value, Convert.ToBase64String( buffer2 ) );
-            serializer.SerializeAsync(deserializedPacket, channel3).Wait();
+                } 
-
+            }
-            Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(channel3.ToArray()));
         }
     }
 }

Tests/MQTTnet.Core.Tests/TestMqttCommunicationAdapter.cs

@@ -1,5 +1,7 @@
 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;
@@ -26,11 +28,15 @@ namespace MQTTnet.Core.Tests
             return Task.FromResult(0);
         }
 
-        public Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout)
+        public Task SendPacketsAsync(TimeSpan timeout, IEnumerable<MqttBasePacket> packets)
         {
             ThrowIfPartnerIsNull();
 
-            Partner.SendPacketInternal(packet);
+            foreach (var packet in packets)
+            {
+                Partner.SendPacketInternal(packet);
+            }
+
             return Task.FromResult(0);
         }
 
@@ -41,6 +47,11 @@ namespace MQTTnet.Core.Tests
             return Task.Run(() => _incomingPackets.Take());
         }
 
+        public IEnumerable<MqttBasePacket> ReceivePackets( CancellationToken cancellationToken )
+        {
+            return _incomingPackets.GetConsumingEnumerable();
+        }
+
         private void SendPacketInternal(MqttBasePacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));

Tests/MQTTnet.TestApp.NetFramework/PerformanceTest.cs

@@ -8,6 +8,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace MQTTnet.TestApp.NetFramework
@@ -17,12 +18,12 @@ namespace MQTTnet.TestApp.NetFramework
         public static async Task RunAsync()
         {
             var server = Task.Run(() => RunServerAsync());
-            var client = Task.Run(() => RunClientAsync(1000, 50000, TimeSpan.FromMilliseconds(10)));
+            var client = Task.Run(() => RunClientAsync(300, TimeSpan.FromMilliseconds(10)));
 
             await Task.WhenAll(server, client).ConfigureAwait(false);
         }
 
-        private static async Task RunClientAsync(int messageChunkSize, int totalMessageCount, TimeSpan interval)
+        private static async Task RunClientAsync( int msgChunkSize, TimeSpan interval )
         {
             try
             {
@@ -77,33 +78,64 @@ namespace MQTTnet.TestApp.NetFramework
 
                 Console.WriteLine("### WAITING FOR APPLICATION MESSAGES ###");
 
-                var applicationMessage = new MqttApplicationMessage(
+                var testMessageCount = 1000;
-                    "A/B/C",
+                var message = CreateMessage();
-                    Encoding.UTF8.GetBytes("Hello World"),
+                var stopwatch = Stopwatch.StartNew();
-                    MqttQualityOfServiceLevel.AtLeastOnce,
+                for (var i = 0; i < testMessageCount; i++)
-                    false
-                );
-
-                var overallCount = 0;
-                while (overallCount < totalMessageCount)
                 {
-                    var stopwatch = Stopwatch.StartNew();
+                    await client.PublishAsync(message);
-                    var count = 0;
-                    for (var i = 0; i < messageChunkSize; i++)
-                    {
-                        //do not await to send as much messages as possible 
-                        await client.PublishAsync(applicationMessage).ConfigureAwait(false);
-                        count++;
-                        overallCount++;
-                    }
-
-                    stopwatch.Stop();
-
-                    Console.WriteLine($"Sent {count} messages within {stopwatch.ElapsedMilliseconds} ms ({stopwatch.ElapsedMilliseconds / (float)count} ms / message).");
-                    await Task.Delay(interval).ConfigureAwait(false);
                 }
 
-                Console.WriteLine($"Completed sending {totalMessageCount} messages.");
+                stopwatch.Stop();
+                Console.WriteLine($"Sent 1000 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 (false)
+                    {
+                        //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} inteded {msgChunkSize / interval.TotalSeconds}" );
+                        msgCount = 0;
+                        last = now;
+                    }
+
+                    await Task.Delay(interval).ConfigureAwait(false);
+                }
             }
             catch (Exception exception)
             {
@@ -111,6 +143,25 @@ namespace MQTTnet.TestApp.NetFramework
             }
         }
 
+        private static MqttApplicationMessage CreateMessage()
+        {
+            return new MqttApplicationMessage(
+                "A/B/C",
+                Encoding.UTF8.GetBytes( "Hello World" ),
+                MqttQualityOfServiceLevel.AtMostOnce,
+                false
+            );
+        }
+
+        private static Task PublishSingleMessage( IMqttClient client, MqttApplicationMessage applicationMessage, ref int count )
+        {
+            Interlocked.Increment( ref count );
+            return Task.Run( () =>
+            {
+                return client.PublishAsync( applicationMessage );
+            } );
+        }
+
         private static void RunServerAsync()
         {
             try
@@ -133,12 +184,12 @@ namespace MQTTnet.TestApp.NetFramework
                 };
                 
                 var mqttServer = new MqttServerFactory().CreateMqttServer(options);
-                var last = DateTime.UtcNow;
+                var last = DateTime.Now;
                 var msgs = 0;
                 mqttServer.ApplicationMessageReceived += (sender, args) => 
                 {
                     msgs++;
-                    var now = DateTime.UtcNow;
+                    var now = DateTime.Now;
                     if (last < now - TimeSpan.FromSeconds(1))
                     {
                         Console.WriteLine($"received {msgs}");