Situation: Bob is listening to a music from his Subsonic server into its
player (say VLC). He gives the music link (its form is http://subsonic-server.url/stream?player=x&pathUtf8Hex=0123456789abcdef(...)&suffix=.ext)
to his friend Alice whose is using another computer and she is not a
Subsonic registered user into the Bob's server.
She can listen to the music. But she should not be able to.
Fix: check is the user is known AND connected.