I suspect it depends on how you're streaming... from the wiki:
9981 - HTTP server (web interface)
9982 - HTSP server (Streaming protocol)
And from the online help for access control:
Streaming Enables access to streaming functionality for HTTP (web).
Advanced Streaming Enables access to advanced streaming function for HTTP (web) - like direct service or whole MPEG-TS stream (mux)..
HTSP Streaming Enables access to streaming for the HTSP protocol (Movian, Kodi etc.).
So I'd presume 9981 is used for HTTP streaming as well as HTSP