Working on the two local machines first, since they're in the same room, and are easier to troubleshoot/test before moving to doing more remote troubleshooting. I should mention that it doesn't work friends only; the game doesn't show up in friends list, that I can't select join game in Steam overlay despite seeing the client account in the overlay, and the "Invite Friends" button is greyed out. And the game doesn't work in LAN or peer-to-peer when setting the game to public; when connecting via LAN/peer-to-peer ends up with the endless "Waiting for Steam verification" screen for the clients even with EAC off.it's just that he said above that both were on the same local network
Excuse me if this doesn't sound right.....if this 'could' be a Steam issue, wouldn't completely uninstalling/reinstalling Steam so that it automatically sets up the ports it wants to use, be an option for these folks? I am about at that point myself. I posted a thread about a handshake issue where I get booted from a dedicated server a couple of times a night. I've tried every single thing that I could think of as well as those who chimed in on my thread and I still have the issue. Reinstalling Steam is the only thing I haven't tried.
I already tried reinstalling Steam on the 3 machines I have. I can say that it didn't help me with this issue. Your mileage may very.