All three are possible, and then some:
- Some sites out there try to »compile« a list of internet radio stations and like to show their users what’s playing (see shoutcast.com, only they let you opt-in and don’t try to »rip« the info from you).
- Someone just checks your station programmatically because for some reason they want to know what’s playing (and maybe tune in).
- You might have registered your stream with some yp (yellow pages) server, so of course they want to know (and show) what’s playing.
- You send an AAC+ stream and Windows Media Player users try to tune in (they can’t without the right plugin, and WMP is dumb enough to retry, and retry …).
- The music industry (yes, they do), trying to check you for sending copyrighted or banned material.
- Shoutcast’s stream checker, if a) you are registered with them, b) apparently also if you’ve registered your station at spacialnet/audiorealm [not sure], and if c) your stream breaks down. Some 1-3 »users« (can’t remember their user agentright now, something with »SHOUTcast«) start »hammering« your stream to check if it goes up again, then vanish after a few minutes.
- And of course stream rippers are notorious for that. They usually »check in« at about the times when a new song starts. (These are automated programs set for recording a list of songs, or programs.)
But as someone said earlier, usually a few of those don’t really hurt the server, so you could just ignore them. The only problem arises if you are running a hosted stream on a third party server that is already near it’s limits, i.e. you usually have 90 listeners and run a 100-slot-stream. Stream rippers can
become a nuisance in that case, because either you have to upgrade (and pay for it) or some »real« listeners might be kept from listening.
Then again, it’s not always easy to distinguish stream rippers from real listeners (and usually not worth the effort), because they can come in lots of disguises (i.e., faking the user agent
field of a standard player like xmms or Winamp). If you have lots of these, you might consider tracing them down and/or banning them.
From experience I can say the best thing is to concentrate on your format, do a good program, use crossfades and talkovers, maybe some drop-ins at times, and all those would-be nuisances will eventually vanish and your real listeners left—enjoying your program.