Feem - Share files offline. No servers. No cloud. No limits.
LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
Squiggle - Squiggle is a free and open-source, peer-to-peer LAN messenger that is lightweight and feature-rich.
MyChat - Secure instant messenger for any network
BORGChat - BORGChat is a LAN messaging software program.
Winpopup LAN Messenger - Winpopup LAN Messenger is a cost-effective Office, Corporate, Enterprise Instant Messaging solution.