224.0.0.1 is actually a multicast address, it's turned into an ethernet broadcast address at the hardware level, and reaches all stations in the local broadcast domain. There seems to be an issue with the Firmware of the AVP I'm using in that it is unnecessarily picky about the WOL packets if it hasn't been soft powered off before, i.e. if I turn it on and off again, it wakes up with 224.0.0.1 as well, until I disconnect it from the mains. I'll use a trigger cable from the extender as a workaround, since there's already 5V, and that should be good enough.

I had downloaded John Welfringer's TCP Mod before, but totally forgotten about it. After installing it, TCP connections are actually working in the simulator.