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.
Bashupload - Upload files from command line to share between servers
MyChat - Secure instant messenger for any network
FilePizza - Open source application used to transfer file via WebRTC and WebTorrent.
BORGChat - BORGChat is a LAN messaging software program.
BlackHole File Transfer - Blockchain-based file transfer. Designed for everyday use.