WinMessenger is an easy to use program that allows you to send and receive messages from computer to computer in real-time without using dedicated servers. It is a shareware intranet messenging application that's easy-to-use, easy to setup and straightforward.
Here are some screenshots to illustrate the features and user interface of this application:
WhatsApp
Zoom Client for Meetings
Slack
Softros LAN Messenger
Altus