I have a PC and a mac on the same network, how do a send data packets between them

i am trying to connect 2 unity programs, one with a server part and one with a client part, to each other on the same network.
One on a PC and one on a Mac.
What the best way to do this

 

First choose a network API. Then follow the documentation for that network API.

 

Thats not what i would call helpful,
which API will allow me to do this

 

All of them except for ones which rely on cloud based services, or use a proprietary server implementation. See this thread for some options:
https://forum.unity.com/threads/wha...of-available-network-solutions-assets.609088/

My answer wasn't helpful, because specific instructions depend on which networking library you're using, but you didn't mention which one you're using. So you first need to pick one. That link should give you an idea of which one(s) you should try, based on what you're actually planning to do with your project. Don't be afraid to try out more than one of them.