by ailurophobe » 19 Oct 2010 04:33
What he said...
The auto NAT detection IIRC asks a G2 hub to send you an UDP packet and assumes that you are firewalled until it receives that packet. (There is probably a time-out too...) The problem is that UDP packets are not guaranteed delivery, it is perfectly legit for a router to drop or delay them if there is congestion. So sometimes this system just won't work even if you actually have correct forwarding. I think there was a feature request about making this more reliable years ago, but telling Shareaza manually you are not firewalled (can accept incoming connections) actually works just fine, so this was never a priority.