Getting the telnetter's host name

Is it possible to easily get the hostname of someone telnetting? Our current process is:

1) log on to the box on your desk
2) telnet into the central server
3) su -root (required for some of the apps being run)
4) export DISPLAY=your host name

Does the server machine keep a record of the telnetter's name that root could access to better automate the process?

Thanks!

the telnet'ers name is sort of vauge ... similar to the 'last' command?

I am sure there is a more elegant method for this, but it escapes while I am rushed at the moment:

export DISPLAY=`who --ips -m | awk '{print $5}'`:0