I submitted this bug to Apple through the proper channels several months back, but I didn't get word back, and neither has it been fixed. Basically, you can't use Rendezvous-discovered HTTP without disabling your web proxy settings entirely. This was only a mild annoyance before, because all it meant was those silly bookmarks in Safari didn't work. With iTunes 4, however, this has graduated to the level of a major annoyance.

The proxy configuration panel in OS X is really, really badly designed. The culprit is the textbox you use to input exceptions: hosts and domains you want to access directly rather than through the proxy. There are no instructions. Do I use wildcards? Do I comma-separate the hostnames? Who knows. It seems to be that you don't use wildcards: the configuration assumes anything that starts with a period is a domain bypass, and you separate hosts with a newline. I worked that out through a long period of experimentation.

The unforgivable part, however is that there is no way to put in a general bypass for all Rendezvous-discovered hosts.

All Rendezvous-enabled hosts belong to the ‘.local’ domain. If I try to put ‘.local’ in the bypass box, OS X doesn't recognise it as being a domain, and helpfully removes the leading period, turning it into the individual host, ‘local’. This, of course, doesn't match the Rendezvous domain, so all my Rendezvous requests go straight to the Proxy server. The proxy server doesn't understand, and quite rightly 404's me.

I re-discovered this bug today because iTunes4 obviously uses HTTP for its song-sharing protocol: I could see my Powerbook's song library advertised on the network, but any attempt to connect to it died. (Without even an error message: I just got booted back to the local library view. Not happy, Apple)

Making this bug even more egregious, the Rendezvous protocol is pretty much limited to your network segment, and thus access to Rendezvous-advertised services should never require a proxy server. The bypass should be implicit.

I resubmitted this as an iTunes bug, maybe they'll pay attention this time.