Q: Apple Airport Express audio streaming

[Roland Latour]

This router apparently uses some kind of network protocol for accepting
streaming audio from iTunes players on Macs and WinPCs. Can anyone give
(or better, point me to) any technical specs on this? Port#s used, for
instance?

I note that Clementine Audio Player under linux can stream audio to this
router, apparently for playback thru the router's audio port and/or
redistribution over the local network. So it can't be a proprietary
protocol. My searches have turned up lots of shallow reviews but no
in-depth explanations.

Thanks for any help you can give.