Fixed WebSocket client stream

Build/MQTTnet.nuspec

@@ -10,9 +10,11 @@
     <iconUrl>https://raw.githubusercontent.com/chkr1011/MQTTnet/master/Images/Logo_128x128.png</iconUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker).</description>
-    <releaseNotes>* [Core] Fixed library reference issues for .NET 4.6 (Thanks to @JanEggers).
+    <releaseNotes>* [Core] Fixed library reference issues for .NET 4.6 and netstandard 2.0 (Thanks to @JanEggers).
 * [Core] Several COM exceptions are now wrapped properly resulting in less warnings in the trace.
+* [Core] Removed application message payload from trace to reduce trace size and increase performance.
 * [Client] Fixed WebSocket sub protocol negotiation for ASP.NET Core 2 servers (Thanks to @JanEggers).
+* [Client] Fixed broken connection after 30 seconds then using WebSocket protocol (Thanks to @ChristianRiedl).
 * [Server] Client connections are now closed when the server is stopped (Thanks to @zhudanfei).
 * [Server] Published messages from the server are now retained (if set) (Thanks to @ChristianRiedl). BREAKING CHANGE!
     </releaseNotes>

Frameworks/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -1,12 +1,8 @@
 using System;
-using System.IO;
 using System.Net.WebSockets;
-using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
-using MQTTnet.Core.Channel;
 using MQTTnet.Core.Server;
-using MQTTnet.Implementations;
 
 namespace MQTTnet.AspNetCore
 {
@@ -47,47 +43,5 @@ namespace MQTTnet.AspNetCore
         {
             StopAsync();
         }
-
-        private class MqttWebSocketServerChannel : IMqttCommunicationChannel, IDisposable
-        {
-            private readonly WebSocket _webSocket;
-
-            public MqttWebSocketServerChannel(WebSocket webSocket)
-            {
-                _webSocket = webSocket ?? throw new ArgumentNullException(nameof(webSocket));
-
-                RawReceiveStream = new WebSocketStream(_webSocket);
-            }
-
-            public Stream SendStream => RawReceiveStream;
-            public Stream ReceiveStream => RawReceiveStream;
-            public Stream RawReceiveStream { get; }
-
-            public Task ConnectAsync()
-            {
-                return Task.CompletedTask;
-            }
-
-            public Task DisconnectAsync()
-            {
-                RawReceiveStream?.Dispose();
-
-                if (_webSocket == null)
-                {
-                    return Task.CompletedTask;
-                }
-
-                return _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
-            }
-
-            public void Dispose()
-            {
-                RawReceiveStream?.Dispose();
-                SendStream?.Dispose();
-                ReceiveStream?.Dispose();
-
-                _webSocket?.Dispose();
-            }
-        }
     }
 }

Frameworks/MQTTnet.AspnetCore/MqttWebSocketServerChannel.cs

@@ -0,0 +1,60 @@
+using System;
+using System.IO;
+using System.Net.WebSockets;
+using System.Threading;
+using System.Threading.Tasks;
+using MQTTnet.Core.Channel;
+using MQTTnet.Implementations;
+
+namespace MQTTnet.AspNetCore
+{
+    public class MqttWebSocketServerChannel : IMqttCommunicationChannel, IDisposable
+    {
+        private WebSocket _webSocket;
+
+        public MqttWebSocketServerChannel(WebSocket webSocket)
+        {
+            _webSocket = webSocket ?? throw new ArgumentNullException(nameof(webSocket));
+
+            SendStream = new WebSocketStream(_webSocket);
+            ReceiveStream = SendStream;
+        }
+
+        public Stream SendStream { get; private set; }
+        public Stream ReceiveStream { get; private set; }
+
+        public Task ConnectAsync()
+        {
+            return Task.CompletedTask;
+        }
+
+        public async Task DisconnectAsync()
+        {
+            if (_webSocket == null)
+            {
+                return;
+            }
+
+            try
+            {
+                await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
+            }
+            finally
+            {
+                Dispose();
+            }
+        }
+
+        public void Dispose()
+        {
+            SendStream?.Dispose();
+            ReceiveStream?.Dispose();
+
+            _webSocket?.Dispose();
+
+            SendStream = null;
+            ReceiveStream = null;
+            _webSocket = null;
+        }
+    }
+}

Frameworks/MQTTnet.NetStandard/Implementations/MqttWebSocketChannel.cs

@@ -11,6 +11,10 @@ namespace MQTTnet.Implementations
 {
     public sealed class MqttWebSocketChannel : IMqttCommunicationChannel, IDisposable
     {
+        // ReSharper disable once MemberCanBePrivate.Global
+        // ReSharper disable once AutoPropertyCanBeMadeGetOnly.Global
+        public static int BufferSize { get; set; } = 4096 * 20; // Can be changed for fine tuning by library user.
+
         private readonly MqttClientWebSocketOptions _options;
         private ClientWebSocket _webSocket;
 
@@ -80,7 +84,7 @@ namespace MQTTnet.Implementations
                 await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None).ConfigureAwait(false);
             }
 
-            _webSocket = null;
+            Dispose();
         }
 
         public void Dispose()

Frameworks/MQTTnet.NetStandard/Implementations/WebSocketStream.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Net.WebSockets;
 using System.Threading;
 using System.Threading.Tasks;
@@ -10,7 +12,9 @@ namespace MQTTnet.Implementations
     public class WebSocketStream : Stream
     {
         private readonly WebSocket _webSocket;
-        
+        private readonly byte[] _chunkBuffer = new byte[MqttWebSocketChannel.BufferSize];
+        private readonly Queue<byte> _buffer = new Queue<byte>(MqttWebSocketChannel.BufferSize);
+
         public WebSocketStream(WebSocket webSocket)
         {
             _webSocket = webSocket ?? throw new ArgumentNullException(nameof(webSocket));
@@ -34,33 +38,9 @@ namespace MQTTnet.Implementations
         {
         }
 
-        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        public override Task FlushAsync(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;
-                count -= response.Count;
-                
-                if (response.MessageType == WebSocketMessageType.Close)
-                {
-                    await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, cancellationToken).ConfigureAwait(false);
-                }
-            }
-
-            if (_webSocket.State == WebSocketState.Closed)
-            {
-                throw new MqttCommunicationException( "connection closed" );
-            }
-
-            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);
+            return Task.FromResult(0);
         }
 
         public override int Read(byte[] buffer, int offset, int count)
@@ -68,11 +48,58 @@ namespace MQTTnet.Implementations
             return ReadAsync(buffer, offset, count).GetAwaiter().GetResult();
         }
 
+        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            var bytesRead = 0;
+
+            // Use existing date from buffer.
+            while (count > 0 && _buffer.Any())
+            {
+                buffer[offset++] = _buffer.Dequeue();
+                count--;
+                bytesRead++;
+            }
+
+            if (count == 0)
+            {
+                return bytesRead;
+            }
+            
+            while (_webSocket.State == WebSocketState.Open)
+            {
+                await FetchChunkAsync(cancellationToken);
+
+                while (count > 0 && _buffer.Any())
+                {
+                    buffer[offset++] = _buffer.Dequeue();
+                    count--;
+                    bytesRead++;
+                }
+
+                if (count == 0)
+                {
+                    return bytesRead;
+                }
+            }
+
+            if (_webSocket.State == WebSocketState.Closed)
+            {
+                throw new MqttCommunicationException("WebSocket connection closed.");
+            }
+
+            return bytesRead;
+        }
+
         public override void Write(byte[] buffer, int offset, int count)
         {
             WriteAsync(buffer, offset, count).GetAwaiter().GetResult();
         }
 
+        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 long Seek(long offset, SeekOrigin origin)
         {
             throw new NotSupportedException();
@@ -82,5 +109,21 @@ namespace MQTTnet.Implementations
         {
             throw new NotSupportedException();
         }
+
+        private async Task FetchChunkAsync(CancellationToken cancellationToken)
+        {
+            var response = await _webSocket.ReceiveAsync(new ArraySegment<byte>(_chunkBuffer, 0, _chunkBuffer.Length), cancellationToken).ConfigureAwait(false);
+
+            for (var i = 0; i < response.Count; i++)
+            {
+                var @byte = _chunkBuffer[i];
+                _buffer.Enqueue(@byte);
+            }
+
+            if (response.MessageType == WebSocketMessageType.Close)
+            {
+                await _webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, cancellationToken).ConfigureAwait(false);
+            }
+        }
     }
 }

Frameworks/MQTTnet.NetStandard/MqttFactory.cs

@@ -23,7 +23,7 @@ namespace MQTTnet
 
         public MqttFactory(IServiceProvider serviceProvider)
         {
-            _serviceProvider = serviceProvider;
+            _serviceProvider = serviceProvider ?? throw new ArgumentNullException(nameof(serviceProvider));
         }
 
         public ILoggerFactory GetLoggerFactory()

MQTTnet.Core/Client/MqttClient.cs

@@ -60,14 +60,14 @@ namespace MQTTnet.Core.Client
                 await _adapter.ConnectAsync(_options.CommunicationTimeout).ConfigureAwait(false);
                 _logger.LogTrace("Connection with server established.");
 
-                await SetupIncomingPacketProcessingAsync().ConfigureAwait(false);
+                await StartReceivingPacketsAsync(_cancellationTokenSource.Token).ConfigureAwait(false);
                 var connectResponse = await AuthenticateAsync(options.WillMessage).ConfigureAwait(false);
 
                 _logger.LogTrace("MQTT connection with server established.");
 
                 if (_options.KeepAlivePeriod != TimeSpan.Zero)
                 {
-                    StartSendKeepAliveMessages(_cancellationTokenSource.Token);
+                    StartSendingKeepAliveMessages(_cancellationTokenSource.Token);
                 }
 
                 IsConnected = true;
@@ -96,7 +96,6 @@ namespace MQTTnet.Core.Client
             finally
             {
                 await DisconnectInternalAsync().ConfigureAwait(false);
-                _scopeHandle.Dispose();
             }
         }
 
@@ -149,36 +148,36 @@ namespace MQTTnet.Core.Client
                 switch (qosGroup.Key)
                 {
                     case MqttQualityOfServiceLevel.AtMostOnce:
-                    {
-                        // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
-                        await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, qosPackets).ConfigureAwait(false);
-                        break;
-                    }
+                        {
+                            // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
+                            await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, qosPackets).ConfigureAwait(false);
+                            break;
+                        }
                     case MqttQualityOfServiceLevel.AtLeastOnce:
-                    {
-                        foreach (var publishPacket in qosPackets)
                         {
-                            publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                            await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket).ConfigureAwait(false);
-                        }
+                            foreach (var publishPacket in qosPackets)
+                            {
+                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                                await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket).ConfigureAwait(false);
+                            }
 
-                        break;
-                    }
+                            break;
+                        }
                     case MqttQualityOfServiceLevel.ExactlyOnce:
-                    {
-                        foreach (var publishPacket in qosPackets)
                         {
-                            publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                            var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket).ConfigureAwait(false);
-                            await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>()).ConfigureAwait(false);
-                        }
+                            foreach (var publishPacket in qosPackets)
+                            {
+                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket).ConfigureAwait(false);
+                                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>()).ConfigureAwait(false);
+                            }
 
-                        break;
-                    }
+                            break;
+                        }
                     default:
-                    {
-                        throw new InvalidOperationException();
-                    }
+                        {
+                            throw new InvalidOperationException();
+                        }
                 }
             }
         }
@@ -191,7 +190,7 @@ namespace MQTTnet.Core.Client
                 Username = _options.Credentials?.Username,
                 Password = _options.Credentials?.Password,
                 CleanSession = _options.CleanSession,
-                KeepAlivePeriod = (ushort) _options.KeepAlivePeriod.TotalSeconds,
+                KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
                 WillMessage = willApplicationMessage
             };
 
@@ -204,24 +203,6 @@ namespace MQTTnet.Core.Client
             return response;
         }
 
-        private async Task SetupIncomingPacketProcessingAsync()
-        {
-            _isReceivingPackets = false;
-
-#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            Task.Factory.StartNew(
-                () => ReceivePackets(_cancellationTokenSource.Token),
-                _cancellationTokenSource.Token,
-                TaskCreationOptions.LongRunning,
-                TaskScheduler.Default).ConfigureAwait(false);
-#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-
-            while (!_isReceivingPackets && _cancellationTokenSource != null && !_cancellationTokenSource.IsCancellationRequested)
-            {
-                await Task.Delay(TimeSpan.FromMilliseconds(100)).ConfigureAwait(false);
-            }
-        }
-
         private void ThrowIfNotConnected()
         {
             if (!IsConnected) throw new MqttCommunicationException("The client is not connected.");
@@ -234,6 +215,8 @@ namespace MQTTnet.Core.Client
 
         private async Task DisconnectInternalAsync()
         {
+            _scopeHandle?.Dispose();
+
             var clientWasConnected = IsConnected;
             IsConnected = false;
 
@@ -258,6 +241,7 @@ namespace MQTTnet.Core.Client
             }
             finally
             {
+                _logger.LogInformation("Disconnected.");
                 Disconnected?.Invoke(this, new MqttClientDisconnectedEventArgs(clientWasConnected));
             }
         }
@@ -324,7 +308,7 @@ namespace MQTTnet.Core.Client
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
-                await SendAsync(new MqttPubAckPacket {PacketIdentifier = publishPacket.PacketIdentifier});
+                await SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
                 return;
             }
 
@@ -337,7 +321,7 @@ namespace MQTTnet.Core.Client
                 }
 
                 FireApplicationMessageReceivedEvent(publishPacket);
-                await SendAsync(new MqttPubRecPacket {PacketIdentifier = publishPacket.PacketIdentifier});
+                await SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
                 return;
             }
 
@@ -363,12 +347,12 @@ namespace MQTTnet.Core.Client
         {
             var packetAwaiter = _packetDispatcher.WaitForPacketAsync(requestPacket, typeof(TResponsePacket), _options.CommunicationTimeout);
             await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, requestPacket).ConfigureAwait(false);
-            return (TResponsePacket) await packetAwaiter.ConfigureAwait(false);
+            return (TResponsePacket)await packetAwaiter.ConfigureAwait(false);
         }
 
         private ushort GetNewPacketIdentifier()
         {
-            return (ushort) Interlocked.Increment(ref _latestPacketIdentifier);
+            return (ushort)Interlocked.Increment(ref _latestPacketIdentifier);
         }
 
         private async Task SendKeepAliveMessagesAsync(CancellationToken cancellationToken)
@@ -390,6 +374,12 @@ namespace MQTTnet.Core.Client
             }
             catch (OperationCanceledException)
             {
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             catch (MqttCommunicationException exception)
             {
@@ -412,7 +402,7 @@ namespace MQTTnet.Core.Client
             }
         }
 
-        private async Task ReceivePackets(CancellationToken cancellationToken)
+        private async Task ReceivePacketsAsync(CancellationToken cancellationToken)
         {
             _logger.LogInformation("Start receiving packets.");
 
@@ -423,6 +413,7 @@ namespace MQTTnet.Core.Client
                     _isReceivingPackets = true;
 
                     var packet = await _adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
+
                     if (cancellationToken.IsCancellationRequested)
                     {
                         return;
@@ -433,6 +424,12 @@ namespace MQTTnet.Core.Client
             }
             catch (OperationCanceledException)
             {
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    return;
+                }
+
+                await DisconnectInternalAsync().ConfigureAwait(false);
             }
             catch (MqttCommunicationException exception)
             {
@@ -458,15 +455,34 @@ namespace MQTTnet.Core.Client
         private void StartProcessReceivedPacket(MqttBasePacket packet, CancellationToken cancellationToken)
         {
 #pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            Task.Run(() => ProcessReceivedPacketAsync(packet), cancellationToken).ConfigureAwait(false);
+            Task.Run(
+                () => ProcessReceivedPacketAsync(packet),
+                cancellationToken).ConfigureAwait(false);
 #pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
         }
 
-        private void StartSendKeepAliveMessages(CancellationToken cancellationToken)
+        private async Task StartReceivingPacketsAsync(CancellationToken cancellationToken)
+        {
+            _isReceivingPackets = false;
+
+#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+            Task.Run(
+                async () => await ReceivePacketsAsync(cancellationToken),
+                cancellationToken).ConfigureAwait(false);
+#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
+
+            while (!_isReceivingPackets && !cancellationToken.IsCancellationRequested)
+            {
+                await Task.Delay(TimeSpan.FromMilliseconds(100), cancellationToken).ConfigureAwait(false);
+            }
+        }
+
+        private void StartSendingKeepAliveMessages(CancellationToken cancellationToken)
         {
 #pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            Task.Factory.StartNew(() => SendKeepAliveMessagesAsync(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Default)
-                .ConfigureAwait(false);
+            Task.Run(
+                async () => await SendKeepAliveMessagesAsync(cancellationToken), 
+                cancellationToken).ConfigureAwait(false);
 #pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
         }
     }

MQTTnet.Core/Packets/MqttPublishPacket.cs

@@ -1,5 +1,4 @@
-using System;
-using MQTTnet.Core.Protocol;
+using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Packets
 {
@@ -19,7 +18,7 @@ namespace MQTTnet.Core.Packets
         {
             return nameof(MqttPublishPacket) +
                 ": [Topic=" + Topic + "]" +
-                " [Payload=" + Convert.ToBase64String(Payload) + "]" +
+                " [PayloadLength=" + Payload?.Length + "]" +
                 " [QoSLevel=" + QualityOfServiceLevel + "]" +
                 " [Dup=" + Dup + "]" +
                 " [Retain=" + Retain + "]" +

MQTTnet.Core/Serializer/MqttPacketReader.cs

@@ -91,7 +91,7 @@ namespace MQTTnet.Core.Serializer
 
                 if (buffer == -1)
                 {
-                    break;
+                    throw new MqttCommunicationException("Connection closed while reading remaining length data.");
                 }
 
                 encodedByte = (byte)buffer;

Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml

@@ -78,6 +78,7 @@
                     </StackPanel>
 
                     <TextBlock>Received messages:</TextBlock>
+                    <CheckBox x:Name="AddReceivedMessagesToList" IsChecked="True">Add received messages to list</CheckBox>
                     <ListBox MinHeight="50" MaxHeight="250" x:Name="ReceivedMessages" Margin="0,0,0,10">
                         <ListBox.ItemTemplate>
                             <DataTemplate>

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

@@ -30,14 +30,14 @@ namespace MQTTnet.TestApp.UniversalWindows
 
         private async void OnTraceMessagePublished(object sender, MqttNetTraceMessagePublishedEventArgs e)
         {
-            await Trace.Dispatcher.RunAsync(CoreDispatcherPriority.High, () =>
+            var text = $"[{e.TraceMessage.Timestamp:yyyy-MM-dd HH:mm:ss.fff}] [{e.TraceMessage.Level}] [{e.TraceMessage.Source}] [{e.TraceMessage.ThreadId}] [{e.TraceMessage.Message}]{Environment.NewLine}";
+            if (e.TraceMessage.Exception != null)
+            {
+                text += $"{e.TraceMessage.Exception}{Environment.NewLine}";
+            }
+            
+            await Trace.Dispatcher.RunAsync(CoreDispatcherPriority.Low, () =>
             {
-                var text = $"[{e.TraceMessage.Timestamp:yyyy-MM-dd HH:mm:ss.fff}] [{e.TraceMessage.Level}] [{e.TraceMessage.Source}] [{e.TraceMessage.ThreadId}] [{e.TraceMessage.Message}]{Environment.NewLine}";
-                if (e.TraceMessage.Exception != null)
-                {
-                    text += $"{e.TraceMessage.Exception}{Environment.NewLine}";
-                }
-
                 Trace.Text += text;
             });
         }
@@ -109,11 +109,13 @@ namespace MQTTnet.TestApp.UniversalWindows
         {
             var item = $"Timestamp: {DateTime.Now:O} | Topic: {eventArgs.ApplicationMessage.Topic} | Payload: {Encoding.UTF8.GetString(eventArgs.ApplicationMessage.Payload)} | QoS: {eventArgs.ApplicationMessage.QualityOfServiceLevel}";
 
-            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+            await Dispatcher.RunAsync(CoreDispatcherPriority.Low, () =>
             {
-                ReceivedMessages.Items.Add(item);
+                if (AddReceivedMessagesToList.IsChecked == true)
+                {
+                    ReceivedMessages.Items.Add(item);
+                }
             });
-
         }
 
         private async void Publish(object sender, RoutedEventArgs e)