Chapter 5. Service Discovery Beyond the Local Link
Zeroconf is designed to make it easy for you to discover services that are close to you. The word close can be ambiguous. You go to your neighborhood coffee shop and the people drinking their cappuccinos at the next table are physically close to you. You may be able to use a Zeroconf-enabled chat client, text editor, or audio application to interact with them, to collaborate on a document, or to listen to their music library. In the preceding three chapters, you have been introduced to the components of Zeroconf that are designed to allow you to painlessly discover and offer services to devices that are close to yours—where close implies proximity in a network sense. Devices on the same link can use IP to communicate with one another and can present a list of available services in a user-friendly format.
As you drink your morning coffee, the person at the next table may be just a couple of feet away, but you may have never met them. They are not what you would describe as close in the sense of someone who is personally close, they just happen to be near you. There are many people who you might describe as being personally close: friends, family members, coworkers, and people you interact with on a regular basis.
If you are a Mac OS X user who uses iChat as your chat client, the differences in these two notions of close are reflected in the two windows you can use to find people to chat with. The Bonjour window shows you names of people ...