Python Telnet connection

Question

I was playing around with python 3.1 when I came to a problem. I want to connect to a telnet server. Here is my code:

import sys
import telnetlib
tn = telnetlib.Telnet("10.0.0.138")
tn.read_until(b"Username :", 2)
tn.write(b"\n")
tn.read_until(b"Password :", 2)
tn.write(b"\n")
tn.read_until(b"=>", 2)
tn.write(b"exit\n")
tn.close

It works to read until "Username :". There is also no error message when writing an emty line. But when i read until "Password :" i get an empty string. I also get an empty string when i read all.

Please help me if you can.

EDIT: Here is the output when i connect to the server via putty.

 Willkommen am THOMSON TG787v
 Plattform:VDNT-D Firmware:8.2.5.0 Seriennummer:CP0919MT238
 Bitte identifizieren Sie sich mit Ihrem Benutzernamen und Kennwort
--------------------------------------------------------------------------------
Username :
Password :
------------------------------------------------------------------------
 ______ Thomson TG787v
 ___/_____/\
 / /\\ 8.2.5.0
 _____/__ / \\
 _/ /\_____/___ \ Copyright (c) 1999-2009, THOMSON
 // / \ /\ \
 _______//_______/ \ / _\/______
 / / \ \ / / / /\
 __/ / \ \ / / / / _\__
 / / / \_______\/ / / / / /\
 /_/______/___________________/ /________/ /___/ \
 \ \ \ ___________ \ \ \ \ \ /
 \_\ \ / /\ \ \ \ \___\/
 \ \/ / \ \ \ \ /
 \_____/ / \ \ \________\/
 /__________/ \ \ /
 \ _____ \ /_____\/
 \ / /\ \ /___\/
 /____/ \ \ /
 \ \ /___\/
 \____\/
------------------------------------------------------------------------
CP0919MT238=>

I pressed return after "Username :" and then after "Password :".

• moinudin: Perhaps there's a newline character you have to read after Username :? Can you show us a stdout dump of a manual telnet session?
• moinudin: The space before the : also looks suspicious. Perhaps it's not meant to be there?

Answer 1

Lol, i had pretty much the same router as you.

Try this, bit of my old code:

tn = telnetlib.Telnet(HOST)
tn.read_until('Username : ')
tn.write(user+ "\r")
tn.read_until("Password : ")
tn.write(password+ "\n")
tn.write("\r")

This is for Python 2, but try just adding the extra space after the semicolon. Also, if this does not work, use wireshark and see what the putty connection is doing and correct your code to match.

• Martin: Hmm ok this is Python 2.x but it works there. I installed Python 2 now and use this code. Thanks.

Answer 2

# Script to Telnet in to a host
# For now I have hardcoded the HOST that can be taken as input if required
#run as " python teli.py ""
import time
import telnetlib
HOST ="www.google.com"
tn=telnetlib.Telnet(HOST,"80")
tn.write("GET /index.html HTTP/1.1\nHost:"+HOST+"\n\n")
l=tn.read_all()
print l

Answer 3

The docs in this link: http://docs.python.org/library/telnetlib.html

It has a sample code at the end under the section "Telnet Example".

You can access the example via: http://docs.python.org/library/telnetlib.html#telnet-example

• Martin: First this is Python 2.x and not 3.x. And i already found this but it didn't work.

Answer 4

Just use xtelnet:

import xtelnet
t = xtelnet.session()
ip = '192.168.0.32' #just an example
t.connect(ip, username='root', password='toor', p=23, timeout=5)
output1 = t.execute('echo ala_is_king')
print(output1)
t.close()

Answer 5

The simple python telnet program below will definitely work on python3.

import telnetlib
import sys
HOST = input("enter your host IP:")
tn=telnetlib.Telnet(HOST)
tn.write(b'admin\n')
tn.write(b'admin123\n')
tn.write(b"enable\n")
tn.write(b"cisco\n")
tn.write(b"conf t \n")
tn.write(b"hostname SIDDHARTH \n")
tn.write(b'interface loopback0\n')
tn.write(b'ip address 1.1.1.1 255.255.255.255\n')
tn.write(b'interface loopback1\n')
tn.write(b'ip address 2.2.2.2 255.255.255.255\n')
tn.write(b"end \n")
tn.write(b"exit \n")
x = tn.read_all()
print (x)