Add server implementation

MQTTnet.Core/Adapter/IMqttCommunicationAdapter.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Threading.Tasks;
+using MQTTnet.Core.Client;
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Adapter
+{
+    public interface IMqttCommunicationAdapter
+    {
+        Task ConnectAsync(MqttClientOptions options, TimeSpan timeout);
+
+        Task DisconnectAsync();
+
+        Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout);
+
+        Task<MqttBasePacket> ReceivePacketAsync(TimeSpan timeout);
+    }
+}