Refactor server socket management for Linux support.

Frameworks/MQTTnet.NetStandard/Server/MqttServerTlsTcpEndpointOptions.cs

@@ -0,0 +1,12 @@
+namespace MQTTnet.Server
+{
+    public class MqttServerTlsTcpEndpointOptions : MqttServerTcpEndpointBaseOptions
+    {
+        public MqttServerTlsTcpEndpointOptions()
+        {
+            Port = 8883;
+        }
+
+        public byte[] Certificate { get; set; }
+    }
+}