BeeBEEP - You can message and share files inside your intranet without a server.
BORGChat - BORGChat is a LAN messaging software program.
Feem - Share files offline. No servers. No cloud. No limits.
Softros LAN messenger - LAN messenger for an internal office chat for home or business users. It does not require a server and is very easy to install and use. It supports personal chats, group chats, message brodcasting, files transfer and remote desktop access.
Winpopup LAN Messenger - Winpopup LAN Messenger is a cost-effective Office, Corporate, Enterprise Instant Messaging solution.
Output Messenger - Secure instant messenger app for office provides seamless instant messaging solutions for all office, corporate and enterprise business communication needs.