Mac Audio

[StuartR]

don't try to use WiFi at all ever, it will not solve any problems. WiFi itself IS a problem.

I don't know where you are getting a report that your buddy is on WiFi. I have never seen that in my sessions.

If everything worked before your buddy got a new router, and then it stopped working, then the thing you need to look at is the new router.

Be aware that many computers can use wired LAN and WiFi at the same time, so it's very important to be certain your WiFi is shut down.
I'm a Mac user - I always disable Wifi on my computers that have a wired connection

That's an important point.