You do not need to have Internet connectivity to use this feature.
WinPopup NET Messenger is a network messaging program ( LAN CHAT ) for Windows, that will allow you to send LAN messages from one computer to another on the same network. You may send the message to the user name or computer name or workgorup name. This program has no relationship whatsoever to the Internet.
( By CEZEO software Ltd. - Winpopup NET messenger Publisher )