iTunes 10.1.1 & Remote Speakers (error -15000)

I recently had a problem with upgrading to iTunes version 10.1.1.4 and playing to my Airport Express for remote speakers.

I spent 3+ hours looking for the resolution until I found it at the below link.

Thanks to you, a lot of people including myself are happy and grateful:

Fix for error -15000 Remote speakers on iTunes / Windows 7

Published on October 22, 2010 in Apple. 46 Comments Tags: airport, airtunes, itunes.
So, just to be clear: this is not about iTunes on MacOSX, it’s only about iTunes 10 on Windows 7. It might work on Windows Vista, but I have no PC with Vista to test. It might help on versions earlier than iTunes 10 (I read the version 8 already had the problem), but I haven’t tested that.

The problem is the following: while it used to be possible (in older versions of iTunes), your iTunes might not stream the music to an Airport Express / Apple TV (the feature they call ‘Airtunes‘), and every time you try, iTunes will come back with an error ‘An error occurred connecting to the remote speaker (…). An unknown error occurred (-15000).‘. What is happening is that the Windows Firewall is blocking the UDP connections for Airtunes (ports 6001-6003 if you’re asking). For some reason the old firewall rules for iTunes don’t work with the new version.
How to fix this: only if you’re not afraid of diving into your PC’s configuration. If you’re a novice or feel unsure, ask someone more knowledgeable to do it for you. Check if the person knows what a firewall is used for. “Security” is a too general answer.
Go to the control panel for Windows Firewall (Start / Control Panel / Security / Windows Firewall)
Go to the ‘Advanced settings’ and look for the ‘Inbound Rules’ (I know, for me iTunes sending music to somewhere else sounds like outbound, but still, it’s the inbound you need).
Look for a rule called “iTunes” (there might be several) and see if it talks about UDP ports, not TCP. The ‘Protocols and Ports’ page should look like this:
Now go to the ‘Advanced’ tab. Your rule will specify only ‘Public’ under the profiles. Also check the ‘Private’ profile. Don’t touch the rest.
Close all your tabs and windows for the Firewall.
Try to connect to the speakers in iTunes. It should work.
How did I find this? I was unnerved enough to look for a while and I checked how the demo version of Airfoil (in short: stream any audio to your Airport Express/AppleTV, not just from iTunes, costs 25$) deals with the Windows firewall.
Hope this helps some people like those writing on various forums.
So, now that I have the music from my laptop playing in my kitchen again, I can continue making my soup. Broccoli, thank for asking.