LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
Feem - Share files offline. No servers. No cloud. No limits.
MyChat - Secure instant messenger for any network
BeeBEEP - You can message and share files inside your intranet without a server.
BORGChat - BORGChat is a LAN messaging software program.
Winpopup LAN Messenger - Winpopup LAN Messenger is a cost-effective Office, Corporate, Enterprise Instant Messaging solution.