Refactor options

MQTTnet.Core/Client/MqttClientTcpOptionsExtensions.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace MQTTnet.Core.Client
+{
+    public static class MqttClientTcpOptionsExtensions
+    {
+        public static int GetPort(this MqttClientTcpOptions options)
+        {
+            if (options == null) throw new ArgumentNullException(nameof(options));
+
+            if (options.Port.HasValue)
+            {
+                return options.Port.Value;
+            }
+
+            return !options.TlsOptions.UseTls ? 1883 : 8883;
+        }
+    }
+}