Zero Configuration Networking: The Definitive Guide

Chapter 10. Ruby, Python, and Other Languages

The preceding chapters covered the DNS Service Discovery programming APIs developed primarily by Apple’s engineers, which include both cross-platform and Mac-specific APIs. The cross-platform C and Java APIs are available on Macintosh, Microsoft Windows, Linux, FreeBSD, Solaris, and other Unix variants. The Mac-specific Core Foundation API and Cocoa API are available for programmers writing software designed solely for Mac OS X.

Those are just the tip of the iceberg. There exist a range of open source projects (e.g., ones that implement higher-level DNS Service Discovery API layers built on top of the C DNSServiceDiscovery API foundation provided by Apple), some of which complement Apple’s work, and some of which overlap or even compete with it. This is made possible by the careful separation of the background daemon and the client library in Apple’s own implementation of Multicast DNS and DNS Service Discovery.

The first component is a background daemon, which runs in its own address space and implements all the protocol logic, timing, packet sending and reception, record caching, and similar functionality. The second component is the client library, which client applications link with, in the application’s address space, in order to communicate with the background daemon. Apple’s background daemon is licensed under the Apple Public Source License 2.0, an FSF-approved open source license. Apple’s client library is licensed under an even ...