LAN Messenger is a p2p chat application for intranet communication and does not require a server. A variety of handy features are supported including notifications, personal and group messaging with encryption, file transfer and message logging.Discontinued
Sadly, no more releases since Dec. 2018
KouChat is a simple serverless chat client for local area networks (wifi). With KouChat you can communicate with other KouChat users, without configuring a server, or accessing the Internet.
Last release 1.1.1 is from August 2018.
AChat enables you to chat on your local network (LAN). But you can also share entire directories or send specific files, show images to other users and send messages even to users who are currently offline. Everything with full Unicode support.This app doesn't have any features at the moment.
Private and Secure Instant Messenger for Office designed specifically for keeping remote employees and multiple offices in sync.
"Give your team the freedom to chat, talk, share and interact together from anywhere, on any devices" by using it.