Windows automate telnet

Question

I would like to run a set of commands that would typically be run in telnet(from c#).

For example I would like to run the following

using System;
using          


        

Answer 1

Based on comments I understand that you can use actual telnet protocol implementation instead of calling to telnet.exe, so

Form1.cs

using MinimalisticTelnet;
using System;
using System.Text.RegularExpressions;
using System.Windows.Forms;

namespace Telnet
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private MinimalisticTelnet.TelnetConnection _tc;

        private void Form1_Load(object sender, EventArgs e)
        {
            _tc = new TelnetConnection("telehack.com", 23);
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            ProcessOutput();
        }

        private void btnSendCommand_Click(object sender, EventArgs e)
        {
            if (_tc.IsConnected)
            {
                _tc.WriteLine(tbCommand.Text.Trim());
                tbCommand.Clear();
                tbCommand.Focus();
                ProcessOutput();
            }
        }

        private void ProcessOutput()
        {
            if (!_tc.IsConnected)
                return;

            var s = _tc.Read();
            s = Regex.Replace(s, @"\x1b\[([0-9,A-Z]{1,2}(;[0-9]{1,2})?(;[0-9]{3})?)?[m|K]?", "");
            tbOutput.AppendText(s);
        }
    }
}

TelnetInterface.cs

// minimalistic telnet implementation
// conceived by Tom Janssens on 2007/06/06  for codeproject
//
// http://www.corebvba.be



using System;
using System.Collections.Generic;
using System.Text;
using System.Net.Sockets;

namespace MinimalisticTelnet
{
    enum Verbs
    {
        WILL = 251,
        WONT = 252,
        DO = 253,
        DONT = 254,
        IAC = 255
    }

    enum Options
    {
        SGA = 3
    }

    class TelnetConnection
    {
        TcpClient tcpSocket;

        int TimeOutMs = 100;

        public TelnetConnection(string Hostname, int Port)
        {
            tcpSocket = new TcpClient(Hostname, Port);

        }

        public string Login(string Username, string Password, int LoginTimeOutMs)
        {
            int oldTimeOutMs = TimeOutMs;
            TimeOutMs = LoginTimeOutMs;
            string s = Read();
            if (!s.TrimEnd().EndsWith(":"))
                throw new Exception("Failed to connect : no login prompt");
            WriteLine(Username);

            s += Read();
            if (!s.TrimEnd().EndsWith(":"))
                throw new Exception("Failed to connect : no password prompt");
            WriteLine(Password);

            s += Read();
            TimeOutMs = oldTimeOutMs;
            return s;
        }

        public void WriteLine(string cmd)
        {
            Write(cmd + Environment.NewLine);
        }

        public void Write(string cmd)
        {
            if (!tcpSocket.Connected) return;
            byte[] buf = System.Text.ASCIIEncoding.ASCII.GetBytes(cmd.Replace("\0xFF", "\0xFF\0xFF"));
            tcpSocket.GetStream().Write(buf, 0, buf.Length);
        }

        public string Read()
        {
            if (!tcpSocket.Connected) return null;
            StringBuilder sb = new StringBuilder();
            do
            {
                ParseTelnet(sb);
                System.Threading.Thread.Sleep(TimeOutMs);
            } while (tcpSocket.Available > 0);
            return sb.ToString();
        }

        public bool IsConnected
        {
            get { return tcpSocket.Connected; }
        }

        void ParseTelnet(StringBuilder sb)
        {
            while (tcpSocket.Available > 0)
            {
                int input = tcpSocket.GetStream().ReadByte();
                switch (input)
                {
                    case -1:
                        break;
                    case (int)Verbs.IAC:
                        // interpret as command
                        int inputverb = tcpSocket.GetStream().ReadByte();
                        if (inputverb == -1) break;
                        switch (inputverb)
                        {
                            case (int)Verbs.IAC:
                                //literal IAC = 255 escaped, so append char 255 to string
                                sb.Append(inputverb);
                                break;
                            case (int)Verbs.DO:
                            case (int)Verbs.DONT:
                            case (int)Verbs.WILL:
                            case (int)Verbs.WONT:
                                // reply to all commands with "WONT", unless it is SGA (suppres go ahead)
                                int inputoption = tcpSocket.GetStream().ReadByte();
                                if (inputoption == -1) break;
                                tcpSocket.GetStream().WriteByte((byte)Verbs.IAC);
                                if (inputoption == (int)Options.SGA)
                                    tcpSocket.GetStream().WriteByte(inputverb == (int)Verbs.DO ? (byte)Verbs.WILL : (byte)Verbs.DO);
                                else
                                    tcpSocket.GetStream().WriteByte(inputverb == (int)Verbs.DO ? (byte)Verbs.WONT : (byte)Verbs.DONT);
                                tcpSocket.GetStream().WriteByte((byte)inputoption);
                                break;
                            default:
                                break;
                        }
                        break;
                    default:
                        sb.Append((char)input);
                        break;
                }
            }
        }
    }
}

This is Windows Forms app with 2 textboxes and 1 button and a timer (interval is 1000ms). I've used code from CodeProject (linked in original question) with some changes to make it actually work.

Answer 2

Coding this may be hard. However, there are free tools out there for Telnet scripting, see Expect for one. If you have an C# application then perhaps your code could generate the Expect script and then run Expect?

Answer 3

Sending the information to telnet seems like it should be straightforward; use SendKeys(). The question becomes how to capture the output.

I found this YouTube video that should help: https://www.youtube.com/watch?v=BDTCviA-5M8

The solution in the video doesn't really address keeping the session open. I'm a bit outside my knowledge area here, but I believe you can start telnet in a worker thread, send commands to it with SendKeys(), capture the output as described in the video, then parse it.

Does that sufficiently resolve the requirement?