Is there a LAN chat app?

It has been bugging me (especially post-Snowden) that we use the internet for everything, even if the person we interact with is in the next room.

I recently found Dukto to send files from one computer to another in the local network.

I was wondering if there is a (OS independent) chat application for LAN. It would be so cool to have all people in the same network in a bar/cafe/uni to communicate with another (yes, you'd need a block function (based on MAC-address?)).

Does something like this exist?

I personally would be cool with that but nobody uses it, I haven't come accross this anywhere except maybe hackerspaces. Restaurant/bar owners would need to set it up, plus you need a computer(the router?) that is always online and tell the people how to enter the chatroom.

I just want a programm that I can fire up whenever I go somewhere with a (Wireless)LAN to see what's going on. Like Firechat for (W)LANs?

Many places I've worked at end up having an internal irc server running on a random debian machine. Works well and there's plenty of clients available

Yeah, that seems to be the way to go but I'd love a less geeky, n00b-friendly solution (pretty sure it doesn't exist but I can't figure out why. Is that so hard to code/achieve?).

IP Messenger http://ipmsg.org/index.html.en