Reset the keep alive monitor if a session is being resumed from a different (or same) client.

Source/MQTTnet/Server/MqttClientKeepAliveMonitor.cs

@@ -50,6 +50,12 @@ namespace MQTTnet.Server
             _isPaused = false;
         }
 
+        public void Reset()
+        {
+            _lastPacketReceivedTracker.Restart();
+            _lastNonKeepAlivePacketReceivedTracker.Restart();
+        }
+
         public void PacketReceived(MqttBasePacket packet)
         {
             _lastPacketReceivedTracker.Restart();

Source/MQTTnet/Server/MqttClientSession.cs

@@ -56,6 +56,11 @@ namespace MQTTnet.Server
 
         public string ClientId { get; }
 
+        public void ResumeSession()
+        {
+            _keepAliveMonitor.Reset();
+        }
+
         public void FillStatus(MqttClientSessionStatus status)
         {
             status.ClientId = ClientId;
@@ -87,11 +92,11 @@ namespace MQTTnet.Server
 
                 _cancellationTokenSource = new CancellationTokenSource();
 
-                //woraround for https://github.com/dotnet/corefx/issues/24430
+                //workaround for https://github.com/dotnet/corefx/issues/24430
 #pragma warning disable 4014
                 _cleanupHandle = _cancellationTokenSource.Token.Register(() => CleanupAsync());
 #pragma warning restore 4014
-                //endworkaround
+                //end workaround
 
                 _wasCleanDisconnect = false;
                 _willMessage = connectPacket.WillMessage;

Source/MQTTnet/Server/MqttClientSessionsManager.cs

@@ -312,6 +312,8 @@ namespace MQTTnet.Server
                     }
                     else
                     {
+                        clientSession.ResumeSession();
+
                         _logger.Verbose("Reusing existing session of client '{0}'.", connectPacket.ClientId);
                     }
                 }