In a network, you can create a tiny chatting channel using netcat. It's lightweight TCP protocol with plain-text transmission, so be carefully on using.
First, create a channel by picking port number (ex: 7777)
$ sudo nc -l 0.0.0.0 7777
Then, tell you friend your IP and channel port. He will use this info to connect the channel
$ nc 192.168.1.2 7777
Finnally, start chatting !! Each message will be send when you press [Enter]
Note: End the session by press
Ctrl + D