BroChat

Allows you to exchange messages and media files within a local network without using the internet.
There is no authorization or centralized messaging server.
It does not requiring users to register with a central database and fully endependent of Internet.

p.s.:
To detect other devices on the local network, the following conditions must be met:
1) The devices must be unlocked and have their screens turned on (this is not required for messaging).
2) They must be connected to the same WiFi network and have the same network mask (this is usually done automatically with automatic IP assignment).