I installed iTunes 5 last week, and immediately lost the ability to see shared iTunes instances on my local network, both at work and at home. Oddly enough, other iTunes users could still see my music, but I could not see them. (I’m using Windows XP Pro, Service Pack 1, by the way.)

Since I don’t have the Windows Firewall running on my LAN connection, my first thought was that Norton Antivirus might perhaps be blocking iTunes, although it had never done so before. But turning off Norton’s Internet Worm Protection category made no difference.

Now, after installing iTunes 5, I had noticed a new process called mDNSResponder.exe on my system. I tracked this down and found that it is a service provided as part of a new Apple component called Bonjour. This made me a little suspicious, but I didn’t spend much time looking at it.

Well, it turns out that Bonjour was the culprit after all. This morning, I consulted the oracle and find a message board thread that gave me a succesful workaround to my problem. It seems that Bonjour acts (among oher things) as a multicast DNS server (which explains the name mDNSResponder). On my system, the only noticeable consequence so far has been that it has prevented iTunes from seeing other iTunes instances on the local network. The workaround was to change the configuration of my network insterface to use explicit DNS servers rather than to reply on DHCP. This might have been impractical for me, since my machine is a laptop that needs to move between different networks, but fortunately I use a utility that allows me to create different network configurations that are selectable at boot time, so it is only momentarily inconvenient.

Given that Bonjour was added to my machine by the iTunes 5 installer, it’s ironic that Bonjour’s only obvious negative effect has been to prevent iTunes from operating properly. So for now, I say: adieu, Bonjour!

Filed by Dave Seidel under Technology