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windowsbatch-fileautomationtelnet

Automate telnet port testing on Windows 7 using batch script

I am using Windows 7 x64. Using a bat script, I need to check whether I am able to connect to some specific ports on a server using telnet. If successfully connected, the server displays a menu, or else a message like this : Connecting To xxxxx...Could not open connection to the host, on port xxxxx: Connect failed.

For my purpose, the server has several ports to be tested and I don't want to complicate things by logging in or navigating menus. I just want a simple output indicating whether the connection was successful or not. Checking for exit status didn't work. I don't want to use Visual Basic. Any idea how check the connection status using a bat script? Currently I check visually and I use the below script to open connections

@ECHO OFF
setlocal EnableDelayedExpansion

echo.
SET /P host_name="Please enter the hostname: "
echo Please enter the port numbers followed by the Enter key: 
echo.
set num=0

:Loop
set /a num=num+1
SET /P mwa_port%num%=""
if "!mwa_port%num%!"=="" (goto Start)
goto Loop

:Start
set /a num=num-1
for /L %%i in (1,1,%num%) do (
 echo Trying to log into port !mwa_port%%i! of %host_name%
 start /min "" "C:\Windows\System32\telnet.exe" %host_name% !mwa_port%%i!
 REM echo Exit Code is %errorlevel%
)

:End
endlocal
echo.
SET /P leave="Press any key to exit.."

Here is a sample output of the script : 

Please enter the hostname : abcdefg.hijkl.mnop
Please enter the port numbers followed by the Enter key:

10001
10002
10003
10004
10005

Trying to log into port 10001 of abcdefg.hijkl.mnop
Trying to log into port 10002 of abcdefg.hijkl.mnop
Trying to log into port 10003 of abcdefg.hijkl.mnop
Trying to log into port 10004 of abcdefg.hijkl.mnop
Trying to log into port 10005 of abcdefg.hijkl.mnop

Press any key to exit..

It then opens 5 telnet windows in minimized state, each one with a menu on successful login

Solution

  • It's a shame you can't use netcat - are all open source options like it off-limits in your environment?

    Even without open source tools, you can still accomplish this task with PowerShell.

    Here's a sample PS script that will try to connect to port 23 on $remoteHost and exit 0 on success, and 1 on failure. (If you need to do more work once connected, a few examples of more complex PowerShell telnet clients are available on the web, such as this one.)

    Place the code in the file "foo.ps1", then run in cmd.exe (or from a .bat file) with "powershell -File foo.ps1". When it exits, the exit code will be stored in %errorlevel%.

    Note you may need to modify your PowerShell script execution policy (or use the "-ExecutionPolicy Bypass" cmdline option) to allow execution of the script - for more info see this documentation from MSFT.

    param(
    [string] $remoteHost = "arbitrary-remote-hostname",
    [int] $port = 23
     )

# Open the socket, and connect to the computer on the specified port
write-host "Connecting to $remoteHost on port $port"
try {
  $socket = new-object System.Net.Sockets.TcpClient($remoteHost, $port)
} catch [Exception] {
  write-host $_.Exception.GetType().FullName
  write-host $_.Exception.Message
  exit 1
}

write-host "Connected.`n"
exit 0