You can use XPC to communicate with your Audio Server Plugin. See QA1811 for more info and code samples.
However that document doesn’t mention that you can also define your own
AudioObjectPropertySelectors and send a few
CoreFoundation objects back and forth between your ASP and any app that can call
There’s more information on custom properties in
The objects you can send and receive from your ASP are:
kAudioServerPlugInCustomPropertyDataTypeCFPropertyList(what ever you can serialise into a property list)
Read more here: Source link