I'm trying to get an app I'm making using the native agk on my mac and get it to talk to my pc.

The network at home seems fine, I can talk to the mac directly from my pc but I cant get the multiplayer part to work, even with the demo projects.

Has anyone else had this problem? or has anyone got any suggestions as to what the problem could be?

You need to make sure the firewall/router are not blocking the IP communication between the two AppGameKit apps. I find it easier to switch off the firewall briefly if I hit a sudden multiplayer problem just to discount this as the cause. The multiplayer example provided with AppGameKit will only move the HOST icon, not the JOINER icon. If you HOST on the PC and JOIN on the MAC (and vice versa), you should be able to control the HOST icon on the second machine.

Thanks Lee!
It ended up being a firewall thing afterall.
The port I selected was being blocked by the windows PC, but I wasn't getting any kind of alert to tell me that a program was trying to use that port and whether I wanted to allow / disallow it.