2.0.1 seems to show a number of ports open on WAN by default

[arad85]

@podilarius:

You might have a Virus program monitoring those ports or something. Try disabling that and the Windows firewall and see if you get a different outcome.

Yup. Avast was picking up the requests and dropping them. That was such an obvious candidate too  >:(::) (where's the head-bashing-against-the-wall smiley when you need it) The XP machine doesn't run any a/v (it's just for testing like I've been doing!) so was reporting correctly.

Still, it was an interesting couple of days debugging (even to the point of setting up a wireshark machine and port mirroring to see what was happening on the network for the first time…) and lesson learned.