True P2P chat client?

GNU Talk is strictly peer-to-peer, and is packaged in most distributions.

P2P client

I did find this application that purports to run on Windows & Linux. It's called TorChat.

excerpt from website

TorChat is a peer to peer instant messenger with a completely decentralized design, built on top of Tor's location hidden services, giving you extremely strong anonymity while being very easy to use without the need to install or configure anything.

TorChat just runs from an USB drive on any Windows PC. (It can run on Linux and Mac too, in fact it was developed on Linux with cross platform usability in mind from the very first moment on, but the installation on other platforms than Windows is a bit more complicated at the moment)

Running your own server

I would suggest just setting up your own chat server. I run ejabberd and it was pretty trivial to setup on my own box and then I give people accounts to access it.

Ejabberd is a XMPP server so any clients such as Pidgin or Empathy. You can also deploy a web based chat client too. This is a fully featured XMPP server that Process One uses within their products so it's extremely capable.

It even has rooms so you can do pretty much everything with it.

Resources

• main site
• wikipedia page
• How to Install eJabberd XMPP Server on Ubuntu

Zeroconf is a protocol designed by Apple for automatic service detection inside a network, for example to detect available printers. It can also be used for chatting!

The implementation for Linux is Avahi, Apple's implementation is called Bonjour, thus the chat protocol is often just called Bonjour.

Popular chat clients like Pidgin and Gajim support this protocol. In Pidgin, you have to create an account for the Bonjour protocol, giving only a nickname. In Gajim it's called Local, which you can enable in the Accounts-window.