Creating a script for a Telnet session

Question

Does anyone know of an easy way to create a script that can connect to a telnet server  do some usual telnet stuff  and then log off   I am dealing with users who are not familiar with telnet and the commands they will need to run   All I want is for them to double-click on a script  and have that script automatically execute the commands for them   You re probably wondering   What platform are the users on    They will be on both Windows and Linux   Implementations in languages like Perl  Java  or Python are acceptable   I see that Perl has a Net   Telnet module   Has anyone used that   My ideal solution would be to create two script files  a BAT file for windows  and a shell script for Linux   While this would make dual maintenance an issue  it would mean I wouldn t have to install Perl Java Python etc    on every machine   Unfortunately  I have not seen any way to automate a telnet session with batch files or shell scripts   Thanks

User · Answer

It may not sound a good idea but i used java and used simple TCP/IP socket programming to connect to a telnet server and exchange communication. ANd it works perfectly if you know the protocol implemented. For SSH etc, it might be tough unless you know how to do the handshake etc, but simple telnet works like a treat.

Another way i tried, was using external process in java System.exec() etc, and then let the windows built in telnet do the job for you and you just send and receive data to the local system process.

User · Answer

Write the telnet session inside a BAT Dos file and execute

User · Answer

Expect is built for this and can handle the input output plus timeouts etc  Note that if you re not a TCL fan  there are Expect modules for Perl Python Java   EDIT  The above page suggests that the Wikipedia Expect entry is a useful resource  -

User · Answer

import telnetlib  user    admin  password     r   def connect A       tnA   telnetlib Telnet A      tnA read until  username     3      tnA write user     n       tnA read until  password     3      tnA write password     n       return tnA def quit telnet tn      tn write  bye n       tn write  quit n

User · Answer

This vbs script reloads a cisco switch  make sure telnet is installed on windows   Option explicit Dim oShell set oShell  Wscript CreateObject  WScript Shell   oShell Run  telnet  WScript Sleep 1000 oShell Sendkeys  open 172 25 15 9   WScript Sleep 1000 oShell Sendkeys  password   WScript Sleep 1000 oShell Sendkeys  en   WScript Sleep 1000 oShell Sendkeys  password   WScript Sleep 1000 oShell Sendkeys  reload   WScript Sleep 1000 oShell Sendkeys     Wscript Quit

User · Answer

Another method is to use netcat  or nc  dependent upon which posix  in the same format as vatine shows or you can create a text file that contains each command on it s own line   I have found that some posix  telnets do not handle redirect correctly  which is why I suggest netcat

User · Answer

I like the example given by Active State using python   Here is the full link   I added the simple log in part from the link but you can get the gist of what you could do   import telnetlib  prdLogBox  142 178 1 3  uid    uid  pwd    yourpassword   tn   telnetlib Telnet prdLogBox  tn read until  login     tn write uid     n   tn read until  Password    tn write pwd     n   tn write  exit n   tn close

User · Answer

Bash shell supports this out-of-box  e g   exec  stream  lt  gt  dev tcp example com 80 printf  GET   HTTP 1 1 nHost  example com nConnection  close n n   gt  amp   stream  cat  lt  amp   stream    To filter and only show some lines  run  grep Example  lt  amp   stream

User · Answer

Couple of questions    Can you put stuff on the device that you re telnetting into  Are the commands executed by the script the same or do they vary by machine user  Do you want the person clicking the icon to have to provide a userid and or password    That said  I wrote some Java a while ago to talk to a couple of IP-enabled power strips  BayTech RPC3s  which might be of use to you   If you re interested I ll see if I can dig it up and post it someplace

User · Answer

Check for the SendCommand tool   You can use it as follows   perl sendcommand pl -i login txt -t cisco -c  show ip route

User · Answer

I ve used various methods for scripting telnet sessions under unix  but the simplest one is probably a sequence of echo and sleep commands  with their output piped into telnet  Piping the output into another command is also a possibility   Silly example    echo password  echo  show ip route   sleep 1  echo  quit      telnet myrouter   This  basicallly  retrieves the routing table of a Cisco router

[scripting] Creating a script for a Telnet session?

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