how to chat between 2 ubuntu machines in network?

I want to know that how we can chat between 2 ubuntu machines in a network.

there are many messengers but we are prohibited from using those who send the files.

any command line chat messenger for 2 ubuntu in network? or GUI will also work.

The simplest way I can think would be using netcat

try this on your own machine in one terminal:

netcat 8080 -l

(this will be the server since we used -l to set it in listen mode)

in the other terminal:

netcat localhost 8080

(this will be the client connecting to the server)

try typing in one of the windows. You can select any port you want for client / server, but privileged ports (below 1024) require root access on the server)

Replace localhost, on the client, with the ip / dns name of the sever you want to connect to if you want to try this over a network

Probably not what you're looking for, but you can just ssh in to limited accounts on each others machines and use wall.