There are several computers connecting to one machine via telnet.. I want to find out which are all the systems/IPs which are connected to the machine via telnet... is it possible to find that out?
The netstat program will tell you what connections are active. You just need to grep the output for those established and connected to the telnet daemon.
sudo netstat --inet -p | grep "/telnetd" | grep ESTABLISHED
(or something very close to that -- I don't have a running telnetd service on my machine to verify the command -- you may have to look at the output of netstat directly and adjust the grep strings)