NetChat
A small, reliable, local network messenger that doesn't need internet
... Smart Screen may block this program. Don't worry, NetChat is virus free. Just watch the video on how to install properly if you have trouble.
Setup Instructions
1. Download NetChat Installer which will download the latest version for you, and follow on screen instructions
2. Setup NetChat by entering your name.
3. Click 'File' --> 'Add Contact'. Enter the name of the person you would like to add, along with their pc name. This can be found by clicking on system.
That's It.