winappxd waits for connection requests (from an appx -c session). When it gets a request, it validates the user id & password from the client. Then it spawns a copy of APPX (which becomes the server).
When the server is spawned, it inherits a bunch of file descriptors from winappxd. One of these file descriptors is the TCP/IP connection from the client. The "-f=" flag tells the server which file descriptor is connected to the client.
After completing the spawn, winappxd closes it's copy of the client file descriptor and the server starts talking to the client on the indicated descriptor.
|