Does Bonjour have any kind of subscription or notification mechanism?
Yes. The reason that many people seem to be unaware that Bonjour also does notification is probably because it is simply an intrinsic property of the discovery protocol. With a well-designed discovery protocol, the same protocol that you use to discover some piece of information is also used to discover changes to that information. Discovery of static information, and discovery of variable information, and discovering when variable information changes are all just different points on the same spectrum. For an example of an application using Bonjour “notifications”, check out iChat. When you change your Status from “Available” to “Away” or type in a status message, all other iChat clients on the local network are notified of the change.
