Program to communicate bw a PC & iMac Pro on same network?

We have a laptop with Windows 7 and an iMac Pro on the same network. Was wondering if there's a program where you can communicate so that the message pops-up on their screen? Sort of like what there is with MSN, but it uses more the network and not so much the internet..

dw, I end up finding a LAN Messenger program called 'Outlook Messenger' - it works on Windows and MAC.

Glad you found something. Looks like you hit us up in the wee hours of the night.