C# UPnP로 인트라넷 통과

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using NATUPNPLib;
using System.Threading;
using System.Text.RegularExpressions;
using System.IO;

namespace _22UPnP    
{
    class Program
    {
        static void Main(string[] args)
        {
            //  Host Name
            string serverName = Dns.GetHostName();
            Console.WriteLine("Server  ：" + serverName);
            //   Host Name  IP  ，  IPv4        IP  。
            IPAddress internalIP = Dns.GetHostEntry(serverName).AddressList
                .Where(i => i.AddressFamily == AddressFamily.InterNetwork)
                .FirstOrDefault();
            Console.WriteLine("Server  IP：" + internalIP);

            UPnPNAT upnp = new UPnPNAT();
            IStaticPortMappingCollection staticPortMappingCollection = upnp.StaticPortMappingCollection;
            if (staticPortMappingCollection == null) 
            {
                Console.WriteLine("        ，        UPnP  。");
                return;
            }

            int internalPort = 3898;//Server    
            int externalPort = 4343;//          

            staticPortMappingCollection.Add(
                externalPort,//    
                "TCP",//    
                internalPort,//    
                internalIP.ToString(),//  IP  
                true,//    
                "UPNP_Test"//  
                );

            Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            EndPoint serverEndPoint = new IPEndPoint(internalIP, internalPort);
            serverSocket.Bind(serverEndPoint);
            serverSocket.Listen(1);
            Console.WriteLine("       ......
");

            Thread serverThread = new Thread(() => {
                Socket socket = null;
                while (true) 
                {
                    if (socket!= null || (socket = serverSocket.Accept()) != null)
                    {
                        byte[] byteRec = new byte[1024*1024];//         
                        int msgLen = socket.Receive(byteRec);
                        string msgRec = Encoding.UTF8.GetString(byteRec,0,msgLen);
                        Console.WriteLine("  Client   ：
{0}", msgRec);
                    }
                }
            });
            serverThread.IsBackground = true;
            serverThread.Start();

            //  IP  
            string externalIP;
            //  
            var regex = @"\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b";
            Console.WriteLine("      IP......");
            using (var webclient = new WebClient())
            {
                var rawRes = webclient.DownloadString("http://checkip.dyndns.org/");
                externalIP = Regex.Match(rawRes, regex).Value;
            }
            
            Console.WriteLine("    IP  ：" + externalIP);


            Thread clientThread = new Thread(() =>
            {
                ClientConnectToServer(IPAddress.Parse(externalIP), externalPort);
            });
            clientThread.Start();
            

            Console.ReadKey();
        }

        static void ClientConnectToServer(IPAddress remoteIP, int remotePort) 
        {
            Socket clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            clientSocket.Connect(new IPEndPoint(remoteIP, remotePort));
            IPEndPoint remoteEndPoint = clientSocket.RemoteEndPoint as IPEndPoint;
            for (int i = 0; i < 3; i++) 
            {
                string msgFromClient = string.Format("Hello, this msg is from Client. 
{2}
[Remote IP: {0}, Remote Port: {1} ]
",
                    remoteEndPoint.Address, remoteEndPoint.Port, DateTime.Now
                );
                byte[] bytes = Encoding.UTF8.GetBytes(msgFromClient);
                //           
                clientSocket.Send(bytes);
                Thread.Sleep(1000);
            }
        }
    }
}