Fix keep alive checks in server

Build/MQTTnet.nuspec

@@ -22,6 +22,7 @@
 * [Server] Added packet statistics for the connected clients.
 * [Server] Fixed a security issue which sends retained packages to a failed subscription.
 * [Server] Fixed the response (MaximumQoS) of a subscription (Thanks to @redbeans2017).
+* [Server] The keep alive timeouts are now checked for every client (Thanks to @RainerMueller82).
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2017</copyright>
     <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 

Frameworks/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -8,7 +8,7 @@ using MQTTnet.Server;
 
 namespace MQTTnet.AspNetCore
 {
-    public class MqttWebSocketServerAdapter : IMqttServerAdapter, IDisposable
+    public sealed class MqttWebSocketServerAdapter : IMqttServerAdapter, IDisposable
     {
         public event EventHandler<MqttServerAdapterClientAcceptedEventArgs> ClientAccepted;
 

Frameworks/MQTTnet.NetStandard/Client/MqttClient.cs

@@ -347,13 +347,8 @@ namespace MQTTnet.Client
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
-                    await Task.Delay(_options.KeepAlivePeriod, cancellationToken).ConfigureAwait(false);
-                    if (cancellationToken.IsCancellationRequested)
-                    {
-                        return;
-                    }
-
                     await SendAndReceiveAsync<MqttPingRespPacket>(new MqttPingReqPacket()).ConfigureAwait(false);
+                    await Task.Delay(_options.KeepAlivePeriod, cancellationToken).ConfigureAwait(false);
                 }
             }
             catch (OperationCanceledException)

Frameworks/MQTTnet.NetStandard/Server/MqttClientPendingMessagesQueue.cs

@@ -10,9 +10,9 @@ using MQTTnet.Protocol;
 
 namespace MQTTnet.Server
 {
-    public sealed class MqttClientPendingMessagesQueue
+    public sealed class MqttClientPendingMessagesQueue : IDisposable
     {
-        private readonly BlockingCollection<MqttPublishPacket> _pendingPublishPackets = new BlockingCollection<MqttPublishPacket>();
+        private readonly BlockingCollection<MqttBasePacket> _queue = new BlockingCollection<MqttBasePacket>();
         private readonly IMqttServerOptions _options;
         private readonly MqttClientSession _session;
         private readonly IMqttNetLogger _logger;
@@ -33,24 +33,24 @@ namespace MQTTnet.Server
                 return;
             }
 
-            Task.Run(async () => await SendPendingPublishPacketsAsync(adapter, cancellationToken), cancellationToken).ConfigureAwait(false);
+            Task.Run(async () => await SendQueuedPacketsAsync(adapter, cancellationToken), cancellationToken).ConfigureAwait(false);
         }
 
-        public void Enqueue(MqttPublishPacket publishPacket)
+        public void Enqueue(MqttBasePacket packet)
         {
-            if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
+            if (packet == null) throw new ArgumentNullException(nameof(packet));
 
-            _pendingPublishPackets.Add(publishPacket);
+            _queue.Add(packet);
             _logger.Trace<MqttClientPendingMessagesQueue>("Enqueued packet (ClientId: {0}).", _session.ClientId);
         }
 
-        private async Task SendPendingPublishPacketsAsync(IMqttChannelAdapter adapter, CancellationToken cancellationToken)
+        private async Task SendQueuedPacketsAsync(IMqttChannelAdapter adapter, CancellationToken cancellationToken)
         {
             try
             {
                 while (!cancellationToken.IsCancellationRequested)
                 {
-                    await SendPendingPublishPacketAsync(adapter, cancellationToken);
+                    await SendQueuedPacketAsync(adapter, cancellationToken);
                 }
             }
             catch (OperationCanceledException)
@@ -62,12 +62,12 @@ namespace MQTTnet.Server
             }
         }
 
-        private async Task SendPendingPublishPacketAsync(IMqttChannelAdapter adapter, CancellationToken cancellationToken)
+        private async Task SendQueuedPacketAsync(IMqttChannelAdapter adapter, CancellationToken cancellationToken)
         {
-            MqttPublishPacket packet = null;
+            MqttBasePacket packet = null;
             try
             {
-                packet = _pendingPublishPackets.Take(cancellationToken);
+                packet = _queue.Take(cancellationToken);
                 await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, packet).ConfigureAwait(false);
 
                 _logger.Trace<MqttClientPendingMessagesQueue>("Enqueued packet sent (ClientId: {0}).", _session.ClientId);
@@ -90,14 +90,22 @@ namespace MQTTnet.Server
                     _logger.Error<MqttClientPendingMessagesQueue>(exception, "Sending publish packet failed (ClientId: {0}).", _session.ClientId);
                 }
 
-                if (packet != null && packet.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+                if (packet is MqttPublishPacket publishPacket)
                 {
-                    packet.Dup = true;
-                    _pendingPublishPackets.Add(packet, CancellationToken.None);
+                    if (publishPacket.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
+                    {
+                        publishPacket.Dup = true;
+                        _queue.Add(packet, CancellationToken.None);
+                    }
                 }
 
                 await _session.StopAsync();
             }
         }
+
+        public void Dispose()
+        {
+            _queue?.Dispose();
+        }
     }
 }

Frameworks/MQTTnet.NetStandard/Server/MqttClientSession.cs

@@ -12,7 +12,7 @@ using MQTTnet.Serializer;
 
 namespace MQTTnet.Server
 {
-    public sealed class MqttClientSession
+    public sealed class MqttClientSession : IDisposable
     {
         private readonly Stopwatch _lastPacketReceivedTracker = Stopwatch.StartNew();
         private readonly Stopwatch _lastNonKeepAlivePacketReceivedTracker = Stopwatch.StartNew();
@@ -57,22 +57,29 @@ namespace MQTTnet.Server
 
         public bool IsConnected => _adapter != null;
 
-        public async Task RunAsync(MqttApplicationMessage willMessage, IMqttChannelAdapter adapter)
+        public async Task RunAsync(MqttConnectPacket connectPacket, IMqttChannelAdapter adapter)
         {
+            if (connectPacket == null) throw new ArgumentNullException(nameof(connectPacket));
             if (adapter == null) throw new ArgumentNullException(nameof(adapter));
 
             try
             {
-                _lastPacketReceivedTracker.Restart();
-                _lastNonKeepAlivePacketReceivedTracker.Restart();
-
                 var cancellationTokenSource = new CancellationTokenSource();
 
-                _willMessage = willMessage;
+                _willMessage = connectPacket.WillMessage;
                 _adapter = adapter;
                 _cancellationTokenSource = cancellationTokenSource;
 
                 _pendingMessagesQueue.Start(adapter, cancellationTokenSource.Token);
+
+                _lastPacketReceivedTracker.Restart();
+                _lastNonKeepAlivePacketReceivedTracker.Restart();
+
+                if (connectPacket.KeepAlivePeriod > 0)
+                {
+                    StartCheckingKeepAliveTimeout(TimeSpan.FromSeconds(connectPacket.KeepAlivePeriod), cancellationTokenSource.Token);
+                }
+
                 await ReceivePacketsAsync(adapter, cancellationTokenSource.Token).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
@@ -136,6 +143,12 @@ namespace MQTTnet.Server
             _pendingMessagesQueue.Enqueue(publishPacket);
         }
 
+        public void Dispose()
+        {
+            _pendingMessagesQueue?.Dispose();
+            _cancellationTokenSource?.Dispose();
+        }
+
         private async Task ReceivePacketsAsync(IMqttChannelAdapter adapter, CancellationToken cancellationToken)
         {
             try
@@ -143,6 +156,14 @@ namespace MQTTnet.Server
                 while (!cancellationToken.IsCancellationRequested)
                 {
                     var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
+
+                    _lastPacketReceivedTracker.Restart();
+
+                    if (!(packet is MqttPingReqPacket))
+                    {
+                        _lastNonKeepAlivePacketReceivedTracker.Restart();
+                    }
+
                     await ProcessReceivedPacketAsync(adapter, packet, cancellationToken).ConfigureAwait(false);
                 }
             }
@@ -163,13 +184,6 @@ namespace MQTTnet.Server
 
         private Task ProcessReceivedPacketAsync(IMqttChannelAdapter adapter, MqttBasePacket packet, CancellationToken cancellationToken)
         {
-            _lastPacketReceivedTracker.Restart();
-
-            if (!(packet is MqttPingReqPacket))
-            {
-                _lastNonKeepAlivePacketReceivedTracker.Restart();
-            }
-
             if (packet is MqttPublishPacket publishPacket)
             {
                 return HandleIncomingPublishPacketAsync(adapter, publishPacket, cancellationToken);
@@ -292,5 +306,42 @@ namespace MQTTnet.Server
             var response = new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier };
             return adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, response);
         }
+
+        private void StartCheckingKeepAliveTimeout(TimeSpan keepAlivePeriod, CancellationToken cancellationToken)
+        {
+            Task.Run(
+                async () => await CheckKeepAliveTimeoutAsync(keepAlivePeriod, cancellationToken).ConfigureAwait(false)
+                , cancellationToken);
+        }
+
+        private async Task CheckKeepAliveTimeoutAsync(TimeSpan keepAlivePeriod, CancellationToken cancellationToken)
+        {
+            try
+            {
+                while (!cancellationToken.IsCancellationRequested)
+                {
+                    // Values described here: [MQTT-3.1.2-24].
+                    if (_lastPacketReceivedTracker.Elapsed.TotalSeconds > keepAlivePeriod.TotalSeconds * 1.5D)
+                    {
+                        _logger.Warning<MqttClientSession>("Client '{0}': Did not receive any packet or keep alive signal.", ClientId);
+                        await StopAsync();
+                        return;
+                    }
+
+                    await Task.Delay(keepAlivePeriod, cancellationToken);
+                }
+            }
+            catch (OperationCanceledException)
+            {
+            }
+            catch (Exception exception)
+            {
+                _logger.Error<MqttClientSession>(exception, "Client '{0}': Unhandled exception while checking keep alive timeouts.", ClientId);
+            }
+            finally
+            {
+                _logger.Trace<MqttClientSession>("Client {0}: Stopped checking keep alive timeout.", ClientId);
+            }
+        }
     }
 }

Frameworks/MQTTnet.NetStandard/Server/MqttClientSessionsManager.cs

@@ -70,7 +70,7 @@ namespace MQTTnet.Server
                     ProtocolVersion = clientAdapter.PacketSerializer.ProtocolVersion
                 });
 
-                await clientSession.Session.RunAsync(connectPacket.WillMessage, clientAdapter).ConfigureAwait(false);
+                await clientSession.Session.RunAsync(connectPacket, clientAdapter).ConfigureAwait(false);
             }
             catch (Exception exception)
             {
@@ -210,9 +210,11 @@ namespace MQTTnet.Server
                 if (isSessionPresent)
                 {
                     if (connectPacket.CleanSession)
-                    {
+                    {   
                         _sessions.Remove(connectPacket.ClientId);
+
                         await clientSession.StopAsync().ConfigureAwait(false);
+                        clientSession.Dispose();
                         clientSession = null;
 
                         _logger.Trace<MqttClientSessionsManager>("Stopped existing session of client '{0}'.", connectPacket.ClientId);

Frameworks/MQTTnet.NetStandard/Server/MqttServer.cs

@@ -71,7 +71,6 @@ namespace MQTTnet.Server
             }
 
             _logger.Info<MqttServer>("Started.");
-
             Started?.Invoke(this, new MqttServerStartedEventArgs());
         }
 

Tests/MQTTnet.TestApp.UniversalWindows/MainPage.xaml

@@ -27,7 +27,9 @@
                     <TextBox x:Name="ClientId"></TextBox>
                     <TextBlock>Clean session:</TextBlock>
                     <CheckBox x:Name="CleanSession" IsChecked="True"></CheckBox>
-
+                    <TextBlock>Keep alive interval:</TextBlock>
+                    <TextBox x:Name="KeepAliveInterval" Text="5"></TextBox>
+                    
                     <StackPanel Orientation="Horizontal">
                         <RadioButton x:Name="UseTcp" IsChecked="True" GroupName="connection">TCP</RadioButton>
                         <RadioButton x:Name="UseWs" GroupName="connection">WS</RadioButton>

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

@@ -103,7 +103,8 @@ namespace MQTTnet.TestApp.UniversalWindows
             };
 
             options.CleanSession = CleanSession.IsChecked == true;
-
+            options.KeepAlivePeriod = TimeSpan.FromSeconds(double.Parse(KeepAliveInterval.Text));
+            
             try
             {
                 if (_mqttClient != null)