commit:

UdPunching.Common/BuindInPeerId.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace UdPunching
+{
+    public static class BuindInPeerId
+    {
+        public static readonly Guid Server = Guid.Empty;
+        public static readonly Guid Invalid = new Guid("ffffffff-ffff-ffff-ffff-ffffffffffff");
+    }
+}

UdPunching.Common/TransferCodec.cs

@@ -7,8 +7,6 @@ namespace UdPunching
 {
     public static class TransferCodec
     {
-        public static readonly Guid InvalidPeerId = new Guid("ffffffff-ffff-ffff-ffff-ffffffffffff");
-
         // [0...15] GUID PeerId
         // [16..19] Encrypted data length prefix (LeInt32)
         // [20..END] Encrypted data content

UdPunching.Common/UdPunching.Common.csproj

@@ -41,6 +41,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="BuindInPeerId.cs" />
     <Compile Include="ExchangeMessageFlags.cs" />
     <Compile Include="ExchangeMessage.cs" />
     <Compile Include="ExchangeMessageSection.cs" />

UdPunching.ExampleW/ExampleForm.cs

@@ -115,7 +115,7 @@ namespace UdPunching.ExampleW
             var peerId = TransferCodec.ReadId(_saeRecv.Buffer);
             if (_saeRecv.RemoteEndPoint.IpEndPointEqualsTo(_serverEndPoint))
             {
-                if (TransferCodec.InvalidPeerId == peerId)
+                if (BuindInPeerId.Invalid == peerId)
                 {
                     Invoke(new Action(() => { StatusLabel.Text = "Server FAILURE"; }));
                 }

UdPunching.Serv/ServProgram.cs

@@ -95,12 +95,12 @@ namespace UdPunching.Serv
                 //TODO: handle request
                 // Exchange request
                 // Exchange relay
-                var replyBytes = TransferCodec.Encode(session.PeerRsa, Guid.Empty, rspMsg.ToBytes());
+                var replyBytes = TransferCodec.Encode(session.PeerRsa, BuindInPeerId.Server, rspMsg.ToBytes());
                 _svrSocket.SendTo(replyBytes, sae.RemoteEndPoint);
             }
             else
             {
-                _svrSocket.SendTo(TransferCodec.InvalidPeerId.ToByteArray(), sae.RemoteEndPoint);
+                _svrSocket.SendTo(BuindInPeerId.Invalid.ToByteArray(), sae.RemoteEndPoint);
             }
         }