I've used Wireshark to identify SSDP packets, and the ones I saw from the ESP8266 node are these:
HTTP/1.1 200 OK
EXT:
CACHE-CONTROL: max-age=1200
SERVER: Arduino/1.0 UPNP/1.1 Philips hue bridge 2012/929000226503
USN: uuid:38323636-4558-4dda-9188-cda0e6875511
ST: urn:schemas-upnp-org:device:Basic:1
LOCATION: http://192.168.3.189:80/description.xml
There are no requests made by any other devices to the description.xml file, so I think that it is not advertising correctly, I see that other upnp devices after advertising get HTTP requests for the xml device description, but not this one. Also I don't see it sending any NOTIFY message.
Is this example working for you? And the ESP device appears on the Windows Explorer?
Thanks!
Fernando