See https://pidgin.im/about/ for more information.
Pidgin is an instant messaging program which lets you log in to accounts on multiple chat networks simultaneously. It runs on Windows, Linux, and other UNIX operating systems. Pidgin is compatible with the following chat networks out of the box: AIM, ICQ, Google Talk, Jabber/XMPP, MSN Messenger, Yahoo!
You can message and share files inside your intranet without a server.
...BeeBEEP works also with VPNs. This serverless application is indispensable in all those places where privacy and security an essential requirement.
For more info visit: https://www.beebeep.net
[ Please read https://sourceforge.net/p/darkbot/news/2014/01/darkbots-revitalization/ ]
Darkbot is a portable IRC chat robot written in the C language that can be taught responses to user inquiries, and even have conversations with them. Darkbot was originally created by Jason Hamilton as an aid for help channels on Intenet Relay Chat.