chatting using NETSEND type of command over network

ok so what i am trying to do is find a way to send messages from one mac to another over the network. something similar to the NETSEND command on a windows box. i have tried everything to my knowledge but just cant seem to fiqure it out. i would like to be able to do it with preinstalled apple software like terminal or something else, that would make it easier for the other person to reply and not have to install any software on their end. i am also hoping it will work on any self created airport networks, so it can be wirelessly. any help would be nice. thanks

If the computers have iChat you can just use Rendezvous which is network chatting