Windows automate telnet

匆匆过客 提交于 2019-12-03 05:01:37

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.

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?

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?

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