Not sure how big a problem this is but thought I'd document it to save others time. If you have a Mac with multiple user accounts logged in and iTunes Sharing only the first account to launch iTunes will bind to port 3689. Further accounts will bind to ports starting with 49152. Unfortunately Meerkat only works with iTunes accounts on 3689 (even if you change the target port).
Closing all iTunes instances across all accounts doesn't change the behavior (the first account to start iTunes will always bind to 3689 and the others will always use the higher ports). However, restarting the Mac will allow you to launch iTunes from a different account first which will then use 3689. This will allow you to use Meerkat with iTunes on the other account.
Hmm, strange. The Bonjour advertisement should be independent of the port, so using the right target port should work ok. There must be something else coming across the Bonjour broadcast from a real iTunes -- there is already a bit of custom metadata in there. I will look into it and see if I can add it.
I looked into this and there is no other info coming over the protocol specific to the port. I also tested it with a tunnel forwarded to port 49152 and iTunes was able to connect and see that account's music.



OK, thanks for looking into it. It must have been something else going on with iTunes that the reboot sorted out. Since the upgrade to iTunes 9 I've had a few issues like that unfortunately.