I'm not completely satisfied by the explanation. I still have that uneasy feeling that you get when you solve a bug, but an unsolved mystery remains. "Also, I still don't know why not all consoles connected to that PC froze."
He didn't mention how the logging was done but if it was over a TCP connection then the send() call probably blocked until it timed out since the sleeping computer didn't close the socket nicely, then it had to re-establish the connection. Although reliability is nice, if I were writing a remote logger for a something like a game, I think I'd use UDP.
Would you not use send() with MSG_DONTWAIT? You get the reliability of TCP and you get feedback if there is any potential blocking. (But I certainly am not a socket guru.)
Are you trying to explain how it's possible for some of the consoles to freeze but others not while talking to the same sleeping computer? If so, I did not understand your explanation.
I believe socket writes don't block until you've filled the internal socket buffer, so it's likely that the unaffected machines simply hadn't done this yet.
