Simple C# telnet server sample

/***********************************************************************

Copyright (c) 2010 Alex Zaitsev

All rights reserved.

Simple C# telnet server sample

You can use this code freely for any commercial or non-commercial

purpose. However if you use this code in your program, you should

add the string "Contains code by Alex Zaitsev, www.az3749.narod.ru"

in your copyright notice text.

***********************************************************************/

using System;

using System.Net.Sockets;

using System.Net;

using System.IO;

using System.Diagnostics;

namespace SimpleTelnetServerSample

{

class AsyncRedirect

{

readonly byte[] buf = new byte[4096];

readonly Stream r, w;

readonly AsyncCallback AsyncCallback_;

public AsyncRedirect(Stream Read, Stream Write) { r = Read; w = Write; AsyncCallback_ = this.AsyncCallback; }

void AsyncCallback(IAsyncResult ar)

{

if (!ar.IsCompleted) return;

int n = 0;

try { n = r.EndRead(ar); }

catch (Exception e) {

Console.WriteLine("EndRead failed:{0}", e);

}

if (n > 0)

{

w.Write(buf, 0, n);

w.Flush();

BeginRead();

}

else

{

Console.WriteLine("read 0 bytes,finished");

w.Close();

}

}

public IAsyncResult BeginRead()

{

return r.BeginRead(buf, 0, buf.Length, AsyncCallback_, null);

}

static void Main(string[] args)

{

var psi = new ProcessStartInfo("cmd.exe");

psi.RedirectStandardInput = psi.RedirectStandardOutput = true;

psi.UseShellExecute = false;

var tcpListener = new TcpListener(IPAddress.Any, 23);

tcpListener.Start();

while (true)

{

var tcpClient = tcpListener.AcceptTcpClient();

var clientStream = tcpClient.GetStream();

var p = Process.Start(psi);

var Pro = new AsyncRedirect(p.StandardOutput.BaseStream, clientStream);

var Tcp = new AsyncRedirect(clientStream, p.StandardInput.BaseStream);

Pro.BeginRead();

Tcp.BeginRead();

}

}

};

}