IRCII should work for this one.

(text based)

Unless you talking about system messages then read 
following man pages:

write
mesg
wall


The Wolf

-> -----Original Message-----
-> From: Don Harrop [mailto:don@nis4u.com]
-> Sent: Thursday, May 25, 2000 4:43 PM
-> To: plug-discuss@lists.PLUG.phoenix.az.us
-> Subject: telnet chat.
-> 
-> 
-> Is the a program you can use to chat with another user 
-> telneted into your
-> linux system?
-> 
-> Don
-> 
-> 
-> _______________________________________________
-> Plug-discuss mailing list  -  Plug-discuss@lists.PLUG.phoenix.az.us
-> http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
->