TCP Hole Punching

I'm trying to implement TCP hole punching with windows socket using mingw toolchain. I think the process is right but the hole doesn't seems to take. I used this as reference.

A and B connect to the server S
S sends to A, B's router IP + the port it used to connect to S
S does the same for B
A start 2 threads:
- One thread tries connecting to B's router with the info sent by S
- The other thread is waiting for an incoming connection on the same port used to connect to its router when it connected to S
B does the same

I have no issue in the code I think since:

A and B does get each other ip and port to use
They are both listening on the port they used to connect to their router when they contacted the server
They are both connecting to the right ip and port but get timed out (code error 10060)

I am missing something ?

EDIT: With the help of process explorer, I see that one of the client managed to establish a connection to the peer. But the peer doesn't seems to consider the connection to be made.

Here is what I captured with Wireshark. For the sake of the example, the server S and the client A are on the same PC. The server S listens on a specific port (8060) redirected to that PC. B still tries to connect on the right IP because it sees that the public address of A sent by S is localhost and therefore u

Edit Report

Use Wireshark to check tcp connection request(3-way Handhsake process) is going properly.
Ensure your Listener thread is having select() to de-multiplex the descriptor.
sockPeerConect(socket used to connect Other peer) is FD_SET() in Listener Thread.

Ensure your are checking

 int Listener Thread()
 {
   while(true)
   {
       FD_SET(sockPeerConn);
       FD_SET(sockServerConn);
       FD_SET(nConnectedSock );
      if (FD_ISSET(sockPeerConect)
      {
        /// and calling accept() in side the
        nConnectedSock = accept( ....);

       }
       if (FD_ISSET(sockServerConn)
       {
        /// receive data from Server
        recv(sockServerConn );

       }
       if (FD_ISSET(nConnectedSock )
       {
        /// Receive data from Other Peer
         recv(nConnectedSock );

       }

   }
  }

5.Ensure you are simultaneously starting peer connection A to B and B to A.
6.Start your Listener Thread Prior to Connection to server and Peer and have Single Listener Thread for receiving Server and Client.

answered 2012-01-11T17:03:30.043

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