Squashed commit of the following:

commit 2d94abdde3
Author: Christian <christian.kratky@googlemail.com>
Date:   Sat Nov 13 10:09:59 2021 +0100

    Update MQTTnet.nuspec

    Update docs.

commit f0ea13c07f
Author: logicaloud <47704763+logicaloud@users.noreply.github.com>
Date:   Sat Nov 13 22:05:54 2021 +1300

    Fix MQTT 3.1.1 session persistence when CleanSession=1 (#1294)

commit 47cd5aa3cd
Author: Volker Milbrandt <milbrandt@users.noreply.github.com>
Date:   Sat Nov 13 10:02:55 2021 +0100

    test ResultCode for invalid credentials (no userName but password) (#1270)

    fix order of parameters in exceptions AreEqual(expected, actual)

commit 258df6bb14
Author: HansM <HansM2013@gmx.de>
Date:   Thu Nov 11 20:10:35 2021 +0100

    Removed IDisposable from MqttClientConnection class. (#1288)

commit 85c3c0b352
Author: SeppPenner <HansM2013@gmx.de>
Date:   Mon Nov 8 08:50:59 2021 +0100

    MQTTnet.noUWP.sln: Removed no longer present MQTTnet.Server project.

Build/MQTTnet.nuspec

@@ -12,34 +12,14 @@
     <requireLicenseAcceptance>true</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</description>
     <releaseNotes>
-* [Core] Added all builders to the MQTT factory.
-* [Core] Removed global logger and refactored logging (BREAKING CHANGE!).
 * [Core] Improved memory management when working with large payloads.
-* [Client] Renamed _MqttClientConnectResult_ to _MqttClientConnectResult_ (BREAKING CHANGE!).
 * [Client] The OS will now choose the best TLS version to use. It is no longer fixed to 1.3 etc. (thanks to @patagonaa, #1271).
 * [Client] Exposed user properties and reason string in subscribe result.
 * [Client] Exposed user properties and reason string in unsubscribe result.
-* [ManagedClient] Extended ReconnectAsync (thanks to @nvsnkv, #1202).
-* [ManagedClient] Improved Amazon AWS support (thanks to @scottbrogden-iheartmedia, #1209). 
-* [ManagedClient] Fixed bug that allowed invalid subscriptions (Thanks to @marcelwinh).
-* [Server] Added support for _RetainHandling_ (MQTTv5, BREAKING CHANGE!).
-* [Server] Added support for _NoLocal_ (MQTTv5, BREAKING CHANGE!).
-* [Server] Added support for _SubscriptionIdentifier_ (MQTTv5, BREAKING CHANGE!).
-* [Server] Server now reports supported features properly after successful connection (MQTTv5, BREAKING CHANGE!).
-* [Server] Fixed a memory/performance leak when using QoS Level 1.
-* [Server] Exposed connection timestamp in client status. 
-* [Server] Refactored connection management code. 
-* [Server] Exposed more details in _MqttServerClientConnectedEventArgs_. 
-* [Server] Processing all pending messages before stopping (thanks to @AblEdge, #1234).
-* [Server] Added support for a custom exception handler in _MqttServerMultiThreadedApplicationMessageInterceptorDelegate_.
-* [Server] Removed logger from _MqttServerMultiThreadedApplicationMessageInterceptorDelegate_ (BREAKING CHANGE!).
-* [Server] Fixed a memory leak when deleting sessions.
-* [Server] Fixed timestamp check in server keep-alive monitor (thanks to @logicaloud, #1277).
 * [Server] Added support for returning individual subscription errors (#80 thanks to @jimch)
 * [Server] Improved topic filter comparisons (support for $).
-* [Server] Fixed wrong "IsSessionPresent" result (thanks to @logicaloud, #1268).
 * [Server] Added more MQTTv5 response information to all interceptors (BREAKING CHANGE!).
-* [MQTTnet.Server] Moved server project to a dedicated GitHub repository.
+* [Server] Improved session management for MQTT v5 (#1294, thanks to @logicaloud).
 Git commit: $gitCommit
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2021</copyright>

MQTTnet.noUWP.sln

@@ -45,8 +45,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.AspNetCore.Tests",
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Tests", "Tests\MQTTnet.Core.Tests\MQTTnet.Tests.csproj", "{9C7106CA-96B8-4ABE-B3B4-9357AB8ACB41}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Server", "Source\MQTTnet.Server\MQTTnet.Server.csproj", "{DADEA836-5CC3-474C-A2D8-4D0F31118CD7}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MQTTnet.Extensions.WebSocket4Net", "Source\MQTTnet.Extensions.WebSocket4Net\MQTTnet.Extensions.WebSocket4Net.csproj", "{9AE2F8DA-4178-470B-B8C4-88BE1DAE7D5F}"
 EndProject
 Global

Source/MQTTnet/Server/Internal/MqttClient.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
@@ -96,11 +96,6 @@ namespace MQTTnet.Server
             ChannelAdapter.ResetStatistics();
         }
 
-        public void Dispose()
-        {
-            _cancellationToken.Dispose();
-        }
-
         public async Task RunAsync()
         {
             _logger.Info("Client '{0}': Session started.", Id);

Source/MQTTnet/Server/Internal/MqttClientSessionsManager.cs

@@ -103,7 +103,7 @@ namespace MQTTnet.Server
                 connAckPacket = _connAckPacketFactory.Create(connectionValidatorContext);
   
                 // Pass connAckPacket so that IsSessionPresent flag can be set if the client session already exists
-                client = await CreateClientConnection(connectPacket, connAckPacket, channelAdapter, connectionValidatorContext.SessionItems).ConfigureAwait(false);
+                client = await CreateClientConnection(connectPacket, connAckPacket, channelAdapter, connectionValidatorContext).ConfigureAwait(false);
 
                 await client.SendPacketAsync(connAckPacket, cancellationToken).ConfigureAwait(false);
 
@@ -138,7 +138,7 @@ namespace MQTTnet.Server
                                 _clients.Remove(client.Id);
                             }
 
-                            if (!_options.EnablePersistentSessions)
+                            if ((!_options.EnablePersistentSessions) || (!clientConnection.Session.IsPersistent))
                             {
                                 await DeleteSessionAsync(client.Id).ConfigureAwait(false);
                             }
@@ -422,11 +422,36 @@ namespace MQTTnet.Server
         async Task<MqttClient> CreateClientConnection(
             MqttConnectPacket connectPacket,
             MqttConnAckPacket connAckPacket,
-            IMqttChannelAdapter channelAdapter, 
+            IMqttChannelAdapter channelAdapter,
-            IDictionary<object, object> sessionItems)
+            MqttConnectionValidatorContext context)
         {
             MqttClient connection;
 
+            bool sessionShouldPersist;
+
+            if (context.ProtocolVersion == MqttProtocolVersion.V500)
+            {
+                // MQTT 5.0 section 3.1.2.11.2
+                // The Client and Server MUST store the Session State after the Network Connection is closed if the Session Expiry Interval is greater than 0 [MQTT-3.1.2-23].
+                //
+                // A Client that only wants to process messages while connected will set the Clean Start to 1 and set the Session Expiry Interval to 0.
+                // It will not receive Application Messages published before it connected and has to subscribe afresh to any topics that it is interested
+                // in each time it connects.
+
+                // Persist if SessionExpiryInterval != 0, but may start with a clean session
+                sessionShouldPersist = context.SessionExpiryInterval != 0;
+            }
+            else
+            {
+                // MQTT 3.1.1 section 3.1.2.4: persist only if 'not CleanSession'
+                //
+                // If CleanSession is set to 1, the Client and Server MUST discard any previous Session and start a new one.
+                // This Session lasts as long as the Network Connection. State data associated with this Session MUST NOT be
+                // reused in any subsequent Session [MQTT-3.1.2-6].
+
+                sessionShouldPersist = !connectPacket.CleanSession;
+            }
+
             using (await _createConnectionSyncRoot.WaitAsync(CancellationToken.None).ConfigureAwait(false))
             {
                 MqttSession session;
@@ -434,14 +459,14 @@ namespace MQTTnet.Server
                 {
                     if (!_sessions.TryGetValue(connectPacket.ClientId, out session))
                     {
-                        session = CreateSession(connectPacket.ClientId, sessionItems);
+                        session = CreateSession(connectPacket.ClientId, sessionItems, context.SessionItems, sessionShouldPersist);
                     }
                     else
                     {
                         if (connectPacket.CleanSession)
                         {
                             _logger.Verbose("Deleting existing session of client '{0}'.", connectPacket.ClientId);
-                            session = CreateSession(connectPacket.ClientId, sessionItems);
+                            session = CreateSession(connectPacket.ClientId, context.SessionItems, sessionShouldPersist);
                         }
                         else
                         {
@@ -548,7 +573,7 @@ namespace MQTTnet.Server
                 _rootLogger);
         }
 
-        MqttSession CreateSession(string clientId, IDictionary<object, object> sessionItems)
+        MqttClientSession CreateSession(string clientId, IDictionary<object, object> sessionItems, bool isPersistent)
         {
             _logger.Verbose("Created a new session for client '{0}'.", clientId);
             

Source/MQTTnet/Server/Internal/MqttSession.cs

@@ -20,23 +20,31 @@ namespace MQTTnet.Server
         readonly MqttClientSessionsManager _clientSessionsManager;
 
         public MqttSession(string clientId,
+            bool isPersistent,
             IDictionary<object, object> items,
             MqttServerOptions serverOptions,
             MqttServerEventContainer eventContainer,
             MqttRetainedMessagesManager retainedMessagesManager,
             MqttClientSessionsManager clientSessionsManager)
         {
+            Id = clientId ?? throw new ArgumentNullException(nameof(clientId));
+            IsPersistent = isPersistent;
+            Items = items ?? throw new ArgumentNullException(nameof(items));
+            
             _serverOptions = serverOptions ?? throw new ArgumentNullException(nameof(serverOptions));
             _clientSessionsManager = clientSessionsManager ?? throw new ArgumentNullException(nameof(clientSessionsManager));
-            Id = clientId ?? throw new ArgumentNullException(nameof(clientId));
+            
-            Items = items ?? throw new ArgumentNullException(nameof(items));
-
             SubscriptionsManager = new MqttClientSubscriptionsManager(this, serverOptions, eventContainer, retainedMessagesManager);
         }
 
         public event EventHandler Deleted;
 
         public string Id { get; }
+        
+        /// <summary>
+        /// Session should persist if CleanSession was set to false (Mqtt3) or if SessionExpiryInterval != 0 (Mqtt5)
+        /// </summary>
+        public bool IsPersistent { get; }
 
         public MqttPacketIdentifierProvider PacketIdentifierProvider { get; } = new MqttPacketIdentifierProvider();
 

Tests/MQTTnet.Core.Tests/Server/General.cs

@@ -1021,7 +1021,7 @@ namespace MQTTnet.Tests.Server
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithPersistentSessions());
 
                 // Create the session including the subscription.
-                var client1 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("a"));
+                var client1 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("a").WithCleanSession(false));
                 await client1.SubscribeAsync("x");
                 await client1.DisconnectAsync();
                 await Task.Delay(500);
@@ -1029,7 +1029,7 @@ namespace MQTTnet.Tests.Server
                 var clientStatus = await server.GetClientsAsync();
                 Assert.AreEqual(0, clientStatus.Count);
 
-                var client2 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("b"));
+                var client2 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("b").WithCleanSession(false));
                 await client2.PublishAsync("x", "1");
                 await client2.PublishAsync("x", "2");
                 await client2.PublishAsync("x", "3");

Tests/MQTTnet.Core.Tests/Server/Security_Tests.cs

@@ -1,4 +1,4 @@
-using System.Threading.Tasks;
+using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Adapter;
 using MQTTnet.Client;
@@ -32,6 +32,7 @@ namespace MQTTnet.Tests.Server
                 var ex = await Assert.ThrowsExceptionAsync<MqttConnectingFailedException>(async () => await client.ConnectAsync(clientOptions));
                 Assert.IsInstanceOfType(ex.InnerException, typeof(MqttProtocolViolationException));
                 Assert.AreEqual("Error while authenticating. If the User Name Flag is set to 0, the Password Flag MUST be set to 0 [MQTT-3.1.2-22].", ex.Message, false);
+                Assert.AreEqual(MqttClientConnectResultCode.UnspecifiedError, ex.ResultCode);
             }
         }
 
@@ -53,7 +54,7 @@ namespace MQTTnet.Tests.Server
             return TestCredentials("x", "x");
         }
 
-        async Task TestCredentials(string userName, string password)
+        private async Task TestCredentials(string userName, string password)
         {
             using (var testEnvironment = CreateTestEnvironment())
             {
@@ -84,7 +85,7 @@ namespace MQTTnet.Tests.Server
                     .Build();
 
                 var ex = await Assert.ThrowsExceptionAsync<MqttConnectingFailedException>(async () => await client.ConnectAsync(clientOptions));
-                Assert.AreEqual(ex.Result.ResultCode, MqttClientConnectResultCode.BadUserNameOrPassword);
+                Assert.AreEqual(MqttClientConnectResultCode.BadUserNameOrPassword, ex.Result.ResultCode);
             }
         }
     }

Tests/MQTTnet.Core.Tests/Server/Session_Tests.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -213,6 +212,58 @@ namespace MQTTnet.Tests.Server
             }
         }
 
+        [TestMethod]
+        public async Task Clean_Session_Persistence()
+        {
+            using (var testEnvironment = new TestEnvironment(TestContext))
+            {
+                // Create server with persistent sessions enabled
+
+                await testEnvironment.StartServer(o => o.WithPersistentSessions());
+
+                const string ClientId = "Client1";
+
+                // Create client with clean session and long session expiry interval
+
+                var client1 = await testEnvironment.ConnectClient(o => o
+                    .WithProtocolVersion(Formatter.MqttProtocolVersion.V311)
+                    .WithTcpServer("127.0.0.1", testEnvironment.ServerPort)
+                    .WithSessionExpiryInterval(9999) // not relevant for v311 but testing impact
+                    .WithCleanSession(true) // start and end with clean session
+                    .WithClientId(ClientId)
+                    .Build()
+                );
+
+                // Disconnect; empty session should be removed from server
+
+                await client1.DisconnectAsync();
+
+                // Simulate some time delay between connections
+
+                await Task.Delay(1000);
+
+                // Reconnect the same client ID without clean session
+
+                var client2 = testEnvironment.CreateClient();
+                var options = testEnvironment.Factory.CreateClientOptionsBuilder()
+                    .WithProtocolVersion(Formatter.MqttProtocolVersion.V311)
+                    .WithTcpServer("127.0.0.1", testEnvironment.ServerPort)
+                    .WithSessionExpiryInterval(9999) // not relevant for v311 but testing impact
+                    .WithCleanSession(false) // see if there is a session
+                    .WithClientId(ClientId)
+                    .Build();
+
+
+                var result = await client2.ConnectAsync(options).ConfigureAwait(false);
+
+                await client2.DisconnectAsync();
+
+                // Session should NOT be present for MQTT v311 and initial CleanSession == true
+
+                Assert.IsTrue(!result.IsSessionPresent, "Session present");
+            }
+        }
+
         async Task<IMqttClient> TryConnect(TestEnvironment testEnvironment, MqttClientOptionsBuilder options)
         {
             try

Tests/MQTTnet.Core.Tests/Server/Status_Tests.cs

@@ -1,4 +1,4 @@
-using System.Linq;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Client;
@@ -80,8 +80,8 @@ namespace MQTTnet.Tests.Server
             {
                 var server = await testEnvironment.StartServer(new MqttServerOptionsBuilder().WithPersistentSessions());
 
-                var c1 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("client1"));
+                var c1 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("client1").WithCleanSession(false));
-                var c2 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("client2"));
+                var c2 = await testEnvironment.ConnectClient(new MqttClientOptionsBuilder().WithClientId("client2").WithCleanSession(false));
 
                 await c1.DisconnectAsync();