* [Server] Added support for complex client IDs.

* [Server] Fixed an issue with not correctly removed old client sessions.
* [Server] Several minor performance improvements.
* [Server] An existing client session is no longer closed if a new client connection is invalid.
* [Client] Added support for sending "CleanSession" flag.

MQTTnet.Core/Client/MqttClient.cs

@@ -53,6 +53,7 @@ namespace MQTTnet.Core.Client
                 ClientId = _options.ClientId,
                 Username = _options.UserName,
                 Password = _options.Password,
+                CleanSession = _options.CleanSession,
                 KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
                 WillMessage = willApplicationMessage
             };

MQTTnet.Core/Client/MqttClientOptions.cs

@@ -14,6 +14,8 @@ namespace MQTTnet.Core.Client
 
         public string ClientId { get; set; } = Guid.NewGuid().ToString().Replace("-", string.Empty);
 
+        public bool CleanSession { get; set; } = true;
+
         public TimeSpan KeepAlivePeriod { get; set; } = TimeSpan.FromSeconds(5);
 
         public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(10);