Help me find instant messaging software

I want to communicate instantly via text with two people in another room on the same local network. They are both on Macs. I am on Windows. I would like their windows to be scalable to personal preference & "always on top". I want to use the local network as opposed to a third party that will send the data up & down an internet pipe &/or bill us. I'd prefer it to not make sounds, or at least be able to disable sounds.

What are my options?

^I want to use the local network.

just use google hangouts

here is another option

LAN Messenger

An intranet chat application that does not require a server.

this seems to be another one. 


i have not used any of these so i  don't know the details i just googled the shit


Yes, I do know how to use google but am looking for direct experience here. Thanks, though.

Didn't there used to be one built into windows Phone Post 3.0

I like Slack