Can I find out who is currently using my Airport Express speakers, and kick them?

If I want to stream music to an AE when someone else is connected, I get a message "The speaker XXX is currently used by someone else".

Right now, both my flatmates are not connected to the AE but I still get that message - the AE seems to be stuck. It appears all I can do is unplug the unit and plug it in again.

Is there a way for me to kick the current user, or at least see who was last connected to it?

Change the WiFi password. If I am not wrong, you can only access AirPlay speakers via WiFi. So change it and the person in question won't be able to connect.

If you want to find out who it is, go on to your router interface something like 192.168.X.X and see who is connected. Most people name their computers, so will probably show up. Sorry if I can't be more specific.

Also, maybe there is a bug with your AE (doubt it). Maybe you should reset it.

When I can't tell which device has a hold of the speakers, I often just reboot the base station. When it comes back i've always been able to grab it first.

I suppose you could also add a password for sharing to reduce the chance someone uses the AirPlay speakers.

Of course if you wanted the satisfaction of doing it surgically you could run tcpdump to sniff the sound packets and the cycle or stop that device, but there is no button to bump one device from the network or the speakers (like there is for the disk sharing on airport extreme and time capsule).

A simple solution is to go to the AirPlay tab in the device's settings panel and uncheck "Enable AirPlay," then update. This will kick everyone off. Wait for it to come back, then re-enable.