These APIs may accommodate this request:
public void onHTTPStreamerRequest(IHTTPStreamerSession httpSession, IHTTPStreamerRequestContext reqContext)
And specific to HLS:
public void onHTTPCupertinoStreamerRequest(HTTPStreamerSessionCupertino httpSession, HTTPStreamerCupertinoRequestContext reqContext)
There is also a validation event handler:
Implement the IVHostHTTPStreamerRequestValidator interface and handle the validateHTTPStreamerRequest event.
You can find more information in the ServerSideAPI guide that ships with Wowza [install-dir]/documentation/WowzaStreamingEngine_ServerSideAPI.pdf
Kind regards,
Salvadore