Re: /dev/tcp telnet negotiation

[Illia Bobyr]

On 4/28/2011 7:09 AM, Allan Pinto wrote:

Hi,
i run a lot telnet scripts using /dev/tcp for cisco routers, lately we
have newer models of cisco routers which have ios-xr which is based on
linux and also some mikrotik routers which are again based on linux,
on these devices when i run my script all i get is  ÿý^Xÿý
ÿý#ÿý'ÿý$ÿý! in my output, no username prompt, on the same device if
if use a netcat -T option which is for telnet negotiation, it works,
Could anyone guide me in the right direction where i can achieve the
same using /dev/tcp
below example script

#!/bin/bash

exec 3<>/dev/tcp/$1/23
sleep 1
echo -e "username">&3
echo -e "password">&3
echo -e "sh ver">&3
#sleep 2
echo -e "logout">&3
cat<&3 > $1.txt

Hi,

Telnet is not just a pipe.  It is a real protocol.  Though, rather a simple one.
What you see is a telnet options negotiation.
See http://www.faqs.org/rfcs/rfc854.html for details.

Ilya Bobyr