Add Edgegap relay transport for Fishnet

Unity/Fishnet/EdgegapTransport/Core/EdgegapClientLayer.cs

@@ -0,0 +1,70 @@
+using LiteNetLib.Utils;
+using System;
+using System.Net;
+
+namespace FishNet.Transporting.Edgegap.Client
+{
+    public class EdgegapClientLayer : LiteNetLib.Layers.PacketLayerBase
+    {
+        private uint _userAuthorizationToken;
+        private uint _sessionAuthorizationToken;
+        private RelayConnectionState _prevState = RelayConnectionState.Disconnected;
+
+        public Action<RelayConnectionState, RelayConnectionState> OnStateChange;
+
+        public EdgegapClientLayer(uint userAuthorizationToken, uint sessionAuthorizationToken)
+            : base(EdgegapProtocol.ClientOverhead)
+        {
+            _userAuthorizationToken = userAuthorizationToken;
+            _sessionAuthorizationToken = sessionAuthorizationToken;
+        }
+
+        public override void ProcessInboundPacket(ref IPEndPoint endPoint, ref byte[] data, ref int offset, ref int length)
+        {
+            NetDataReader reader = new NetDataReader(data, offset, length);
+
+            var messageType = (MessageType)reader.GetByte();
+            if (messageType == MessageType.Ping)
+            {
+                var currentState = (RelayConnectionState)reader.GetByte();
+
+                if (currentState != _prevState && OnStateChange != null)
+                {
+                    OnStateChange(_prevState, currentState);
+                }
+
+                _prevState = currentState;
+            }
+            else if (messageType != MessageType.Data)
+            {
+                // Invalid.
+                length = 0;
+                return;
+            }
+
+            length = reader.AvailableBytes;
+            Buffer.BlockCopy(data, reader.Position, data, 0, length);
+        }
+
+        public override void ProcessOutBoundPacket(ref IPEndPoint endPoint, ref byte[] data, ref int offset, ref int length)
+        {
+            NetDataWriter writer = new NetDataWriter(true, length + EdgegapProtocol.ClientOverhead);
+
+            writer.Put(_userAuthorizationToken);
+            writer.Put(_sessionAuthorizationToken);
+
+            // Handle ping
+            if (length == 0) 
+                writer.Put((byte)MessageType.Ping);
+            else if (_prevState == RelayConnectionState.Valid)
+            {
+                writer.Put((byte)MessageType.Data);
+                writer.Put(data, offset, length);
+            } else
+                length = 0; // Drop the packet if the relay isn't ready
+
+            Buffer.BlockCopy(writer.Data, 0, data, 0, writer.Length);
+            length = writer.Length;
+        }
+    }
+}