Added interceptor for application messages

MQTTnet.Core/Internal/MqttApplicationMessageExtensions.cs

@@ -6,12 +6,13 @@ namespace MQTTnet.Core.Internal
     {
         public static MqttApplicationMessage ToApplicationMessage(this MqttPublishPacket publishPacket)
         {
-            return new MqttApplicationMessage(
-                publishPacket.Topic,
-                publishPacket.Payload,
-                publishPacket.QualityOfServiceLevel,
-                publishPacket.Retain
-            );
+            return new MqttApplicationMessage
+            { 
+                Topic = publishPacket.Topic,
+                Payload = publishPacket.Payload,
+                QualityOfServiceLevel = publishPacket.QualityOfServiceLevel,
+                Retain = publishPacket.Retain
+            };
         }
 
         public static MqttPublishPacket ToPublishPacket(this MqttApplicationMessage applicationMessage)

MQTTnet.Core/MqttApplicationMessage.cs

@@ -5,6 +5,11 @@ namespace MQTTnet.Core
 {
     public sealed class MqttApplicationMessage
     {
+        public MqttApplicationMessage()
+        {
+        }
+
+        [Obsolete("Use object initializer or _MqttApplicationMessageBuilder_ instead.")]
         public MqttApplicationMessage(string topic, byte[] payload, MqttQualityOfServiceLevel qualityOfServiceLevel, bool retain)
         {
             Topic = topic ?? throw new ArgumentNullException(nameof(topic));
@@ -13,12 +18,12 @@ namespace MQTTnet.Core
             Retain = retain;
         }
 
-        public string Topic { get; }
+        public string Topic { get; set; }
 
-        public byte[] Payload { get; }
+        public byte[] Payload { get; set; }
 
-        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; }
+        public MqttQualityOfServiceLevel QualityOfServiceLevel { get; set; }
 
-        public bool Retain { get; }
+        public bool Retain { get; set; }
     }
 }

MQTTnet.Core/MqttApplicationMessageBuilder.cs

@@ -13,7 +13,7 @@ namespace MQTTnet.Core
         private string _topic;
         private byte[] _payload;
         private bool _retain;
-        
+
         public MqttApplicationMessageBuilder WithTopic(string topic)
         {
             _topic = topic;
@@ -102,7 +102,13 @@ namespace MQTTnet.Core
                 throw new MqttProtocolViolationException("Topic is not set.");
             }
 
-            return new MqttApplicationMessage(_topic, _payload ?? new byte[0], _qualityOfServiceLevel, _retain);
+            return new MqttApplicationMessage
+            {
+                Topic = _topic,
+                Payload = _payload ?? new byte[0],
+                QualityOfServiceLevel = _qualityOfServiceLevel,
+                Retain = _retain
+            };
         }
     }
 }

MQTTnet.Core/Serializer/MqttPacketSerializer.cs

@@ -65,7 +65,7 @@ namespace MQTTnet.Core.Serializer
                 case MqttUnsubscribePacket unsubscribePacket: return Serialize(unsubscribePacket, writer);
                 case MqttUnsubAckPacket unsubAckPacket: return Serialize(unsubAckPacket, writer);
                 default: throw new MqttProtocolViolationException("Packet type invalid.");
-            }           
+            }
         }
 
         private static MqttBasePacket Deserialize(MqttPacketHeader header, MqttPacketReader reader)
@@ -233,11 +233,13 @@ namespace MQTTnet.Core.Serializer
 
             if (willFlag)
             {
-                packet.WillMessage = new MqttApplicationMessage(
-                    reader.ReadStringWithLengthPrefix(),
-                    reader.ReadWithLengthPrefix(),
-                    (MqttQualityOfServiceLevel)willQoS,
-                    willRetain);
+                packet.WillMessage = new MqttApplicationMessage
+                {
+                    Topic = reader.ReadStringWithLengthPrefix(),
+                    Payload = reader.ReadWithLengthPrefix(),
+                    QualityOfServiceLevel = (MqttQualityOfServiceLevel)willQoS,
+                    Retain = willRetain
+                };
             }
 
             if (usernameFlag)

MQTTnet.Core/Server/MqttClientRetainedMessagesManager.cs

@@ -3,15 +3,14 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using MQTTnet.Core.Diagnostics;
-using MQTTnet.Core.Internal;
 using MQTTnet.Core.Packets;
 
 namespace MQTTnet.Core.Server
 {
     public sealed class MqttClientRetainedMessagesManager
     {
+        private readonly Dictionary<string, MqttApplicationMessage> _retainedMessages = new Dictionary<string, MqttApplicationMessage>();
         private readonly MqttNetTrace _trace;
-        private readonly Dictionary<string, MqttPublishPacket> _retainedMessages = new Dictionary<string, MqttPublishPacket>();
         private readonly MqttServerOptions _options;
 
         public MqttClientRetainedMessagesManager(MqttServerOptions options, MqttNetTrace trace)
@@ -35,7 +34,7 @@ namespace MQTTnet.Core.Server
                     _retainedMessages.Clear();
                     foreach (var retainedMessage in retainedMessages)
                     {
-                        _retainedMessages[retainedMessage.Topic] = retainedMessage.ToPublishPacket();
+                        _retainedMessages[retainedMessage.Topic] = retainedMessage;
                     }
                 }
             }
@@ -45,25 +44,25 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public async Task HandleMessageAsync(string clientId, MqttPublishPacket publishPacket)
+        public async Task HandleMessageAsync(string clientId, MqttApplicationMessage applicationMessage)
         {
-            if (publishPacket == null) throw new ArgumentNullException(nameof(publishPacket));
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
 
-            List<MqttPublishPacket> allRetainedMessages;
+            List<MqttApplicationMessage> allRetainedMessages;
             lock (_retainedMessages)
             {
-                if (publishPacket.Payload?.Any() == false)
+                if (applicationMessage.Payload?.Any() == false)
                 {
-                    _retainedMessages.Remove(publishPacket.Topic);
-                    _trace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' cleared retained message for topic '{1}'.", clientId, publishPacket.Topic);
+                    _retainedMessages.Remove(applicationMessage.Topic);
+                    _trace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' cleared retained message for topic '{1}'.", clientId, applicationMessage.Topic);
                 }
                 else
                 {
-                    _retainedMessages[publishPacket.Topic] = publishPacket;
-                    _trace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' updated retained message for topic '{1}'.", clientId, publishPacket.Topic);
+                    _retainedMessages[applicationMessage.Topic] = applicationMessage;
+                    _trace.Information(nameof(MqttClientRetainedMessagesManager), "Client '{0}' updated retained message for topic '{1}'.", clientId, applicationMessage.Topic);
                 }
 
-                allRetainedMessages = new List<MqttPublishPacket>(_retainedMessages.Values);
+                allRetainedMessages = new List<MqttApplicationMessage>(_retainedMessages.Values);
             }
 
             try
@@ -71,7 +70,7 @@ namespace MQTTnet.Core.Server
                 // ReSharper disable once UseNullPropagation
                 if (_options.Storage != null)
                 {
-                    await _options.Storage.SaveRetainedMessagesAsync(allRetainedMessages.Select(p => p.ToApplicationMessage()).ToList());
+                    await _options.Storage.SaveRetainedMessagesAsync(allRetainedMessages);
                 }
             }
             catch (Exception exception)
@@ -80,9 +79,9 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public List<MqttPublishPacket> GetMessages(MqttSubscribePacket subscribePacket)
+        public List<MqttApplicationMessage> GetMessages(MqttSubscribePacket subscribePacket)
         {
-            var retainedMessages = new List<MqttPublishPacket>();
+            var retainedMessages = new List<MqttApplicationMessage>();
             lock (_retainedMessages)
             {
                 foreach (var retainedMessage in _retainedMessages.Values)

MQTTnet.Core/Server/MqttClientSession.cs

@@ -72,7 +72,7 @@ namespace MQTTnet.Core.Server
         {
             if (_willMessage != null)
             {
-                _mqttClientSessionsManager.DispatchPublishPacket(this, _willMessage.ToPublishPacket());
+                _mqttClientSessionsManager.DispatchApplicationMessage(this, _willMessage);
             }
 
             _cancellationTokenSource?.Cancel(false);
@@ -175,27 +175,30 @@ namespace MQTTnet.Core.Server
             var retainedMessages = _mqttClientSessionsManager.RetainedMessagesManager.GetMessages(subscribePacket);
             foreach (var publishPacket in retainedMessages)
             {
-                EnqueuePublishPacket(publishPacket);
+                EnqueuePublishPacket(publishPacket.ToPublishPacket());
             }
         }
 
         private async Task HandleIncomingPublishPacketAsync(IMqttCommunicationAdapter adapter, MqttPublishPacket publishPacket)
         {
-            if (publishPacket.Retain)
+            var applicationMessage = publishPacket.ToApplicationMessage();
+            _options.ApplicationMessageInterceptor?.Invoke(applicationMessage);
+
+            if (applicationMessage.Retain)
             {
-                await _mqttClientSessionsManager.RetainedMessagesManager.HandleMessageAsync(ClientId, publishPacket);
+                await _mqttClientSessionsManager.RetainedMessagesManager.HandleMessageAsync(ClientId, applicationMessage);
             }
 
-            switch (publishPacket.QualityOfServiceLevel)
+            switch (applicationMessage.QualityOfServiceLevel)
             {
                 case MqttQualityOfServiceLevel.AtMostOnce:
                     {
-                        _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
+                        _mqttClientSessionsManager.DispatchApplicationMessage(this, applicationMessage);
                         return;
                     }
                 case MqttQualityOfServiceLevel.AtLeastOnce:
                     {
-                        _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
+                        _mqttClientSessionsManager.DispatchApplicationMessage(this, applicationMessage);
 
                         await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token,
                             new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
@@ -210,7 +213,7 @@ namespace MQTTnet.Core.Server
                             _unacknowledgedPublishPackets.Add(publishPacket.PacketIdentifier);
                         }
 
-                        _mqttClientSessionsManager.DispatchPublishPacket(this, publishPacket);
+                        _mqttClientSessionsManager.DispatchApplicationMessage(this, applicationMessage);
 
                         await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token,
                             new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });

MQTTnet.Core/Server/MqttClientSessionsManager.cs

@@ -117,11 +117,11 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        public void DispatchPublishPacket(MqttClientSession senderClientSession, MqttPublishPacket publishPacket)
+        public void DispatchApplicationMessage(MqttClientSession senderClientSession, MqttApplicationMessage applicationMessage)
         {
             try
             {
-                var eventArgs = new MqttApplicationMessageReceivedEventArgs(senderClientSession?.ClientId, publishPacket.ToApplicationMessage());
+                var eventArgs = new MqttApplicationMessageReceivedEventArgs(senderClientSession?.ClientId, applicationMessage);
                 ApplicationMessageReceived?.Invoke(this, eventArgs);
             }
             catch (Exception exception)
@@ -133,7 +133,7 @@ namespace MQTTnet.Core.Server
             {
                 foreach (var clientSession in _clientSessions.Values.ToList())
                 {
-                    clientSession.EnqueuePublishPacket(publishPacket);
+                    clientSession.EnqueuePublishPacket(applicationMessage.ToPublishPacket());
                 }
             }
         }

MQTTnet.Core/Server/MqttServer.cs

@@ -4,7 +4,6 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Core.Adapter;
 using MQTTnet.Core.Diagnostics;
-using MQTTnet.Core.Internal;
 
 namespace MQTTnet.Core.Server
 {
@@ -42,7 +41,8 @@ namespace MQTTnet.Core.Server
         {
             if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
 
-            _clientSessionsManager.DispatchPublishPacket(null, applicationMessage.ToPublishPacket());
+            _options.ApplicationMessageInterceptor?.Invoke(applicationMessage);
+            _clientSessionsManager.DispatchApplicationMessage(null, applicationMessage);
         }
 
         public async Task StartAsync()

MQTTnet.Core/Server/MqttServerOptions.cs

@@ -16,6 +16,8 @@ namespace MQTTnet.Core.Server
 
         public Func<MqttConnectPacket, MqttConnectReturnCode> ConnectionValidator { get; set; }
 
+        public Action<MqttApplicationMessage> ApplicationMessageInterceptor { get; set; }
+
         public IMqttServerStorage Storage { get; set; }
     }
 }