Can you use netcat in UDP mode to poke at the 21075 socket, to see if anything's happening at all? Actually, given that it's UDP, it might not work at all.

Oooh, ooh, are you running with admin privileges? I don't think that ARMGR should need them, but you never know.

If you want to poke around some more, I've attached the source code for the udp_test program. It used to compile under g++, but I've not tried for a while, so some Win32-isms might have crept in. It's only 160-odd lines, and you should be able to convert it to Perl or something.