Fix breaking changes.

MQTTnet.Core/Client/MqttClientOptions.cs

@@ -2,11 +2,13 @@
 
 namespace MQTTnet.Core.Client
 {
-    public class MqttClientOptions
+    public sealed class MqttClientOptions
     {
         public string Server { get; set; }
 
-        public int Port { get; set; } = 1883;
+        public int? Port { get; set; }
+        
+        public MqttClientSslOptions SslOptions { get; } = new MqttClientSslOptions();
 
         public string UserName { get; set; }
 
@@ -19,24 +21,5 @@ namespace MQTTnet.Core.Client
         public TimeSpan KeepAlivePeriod { get; set; } = TimeSpan.FromSeconds(5);
 
         public TimeSpan DefaultCommunicationTimeout { get; set; } = TimeSpan.FromSeconds(10);
-
-        /// <summary>
-        /// Use SSL to communicate with the MQTT server.
-        /// </summary>
-        /// <remarks>Setting this value to <c>true</c> will also set <see cref="Port"/> to <c>8883</c> if its value was <c>1883</c> (not set).</remarks>
-        public bool UseSSL
-        {
-            get => _useSSL;
-            set
-            {
-                // Automatically set the port to the MQTT SSL port (8883) if it wasn't set already
-                if (value && Port == 1883)
-                    Port = 8883;
-
-                _useSSL = value;
-            }
-        }
-
-        private bool _useSSL;
     }
 }