TCP Hole Punching

gistfile1.cs

using System;
using System.Linq;
using System.Net.Sockets;
using System.Net;


namespace TCPPunch
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Count() != 3)
            {
                Console.WriteLine("Incorrect args");
            }
            var remote_endpoint = new IPEndPoint(IPAddress.Parse(args[0]), int.Parse(args[1]));
            var local_endpoint = new IPEndPoint(IPAddress.Any, int.Parse(args[2]));

            Console.WriteLine("Punching hole...");
            using (var outgoing = new TcpClient(local_endpoint))
            {
                try
                {
                    outgoing.Connect(remote_endpoint);
                    Console.WriteLine("Made outgoing connection. Exiting.");
                    return;
                }
                catch (Exception ex)
                {
                    if (!(ex.Message.StartsWith("No connection could be made because the target machine actively refused it") || ex.Message.StartsWith("A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond")))
                        throw;
                }
            }
            Console.WriteLine("Hole should be punched");
            var l = new TcpListener(local_endpoint);
            l.Start();
            using (l.AcceptTcpClient())
            {
                Console.WriteLine("Recieve connection");
            }
        }
    }
}