Is telnet even running ? Most distributions don't even install the telnet daemon since it is so insecure..
it-etch:~# netstat -alnp | grep ssh
tcp6 0 0 :::22 :::* LISTEN 3432/sshd
That being said you can use netstat to check the open ports and grep for telnetd.
I don't have telnet running for the reasons I mentioned above so I used sshd in my example..
the port ssh is listening on is 22
If you did install telnet and can't get to it, it might be blocked by your local firewall