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Introduction

The DNSServiceDiscovery API is part of Bonjour, Apple’s implementation of zero-configuration networking (ZEROCONF).

Bonjour allows you to register a network service, such as a printer or file server, so that it can be found by name or browsed for by service type and domain. Using Bonjour, applications can discover what services are available on the network, along with all necessary access information—such as name, IP address, and port number—for a given service.

In effect, Bonjour combines the functions of a local DNS server and AppleTalk. Bonjour allows applications to provide user-friendly printer and server browsing, among other things, over standard IP networks. It does this by combining protocols such as multicast and DNS to add new functionality to the network (such as multicast DNS).

This gives applications easy access to services over local IP networks without requiring the service or the application to support an AppleTalk or Netbeui stack, and without requiring a DNS server for the local network.

For a detailed overview of Bonjour, see “Bonjour Overview”

For additional information on Bonjour, including links to standards, specifications, and resources, see http://developer.apple.com/networking/bonjour/.

This section describes the functions, callbacks, and data structures that make up the DNSServiceDiscovery API.

In this section:

Who Should Use this API
Requirements
Limitations

Who Should Use this API

The DNSServiceDiscovery API is appropriate for Darwin programmers and developers who are comfortable working in Mac OS X at the Mach level. This is a low-level API that interacts directly with the Mach kernel and the mDNS responder daemon.

Bonjour provides two higher-level APIs as alternatives to this one. Cocoa developers should generally use the NSNetServices API documented in Bonjour Overview and Carbon developers should generally use the CFNetServices API documented in CFNetwork Programming Guide.

These higher-level APIs provide the similar services to the DNSServiceDiscovery API and are designed to fit cleanly with code written using a specific framework. Note, however, that the DNSServiceDiscovery API provides a finer degree of control than the CFNetServices and NSNetServices APIs.

Requirements

Version 10.2 or later of the Mac OS X or Darwin operating system is required.

This API requires the services of an mDNS responder. Mac OS X, versions 10.2 and later, include an mDNS responder daemon as part of the operating system. Apple also provides source code for an mDNS responder to Darwin developers as part of versions 10.2 and later.

Limitations

The DNSServiceDiscovery API does not perform network access setup for services. Similarly, the DNSServiceDiscovery API does not provide a network connection from an application to a service. It allows applications to browse for services, or to ask for them by name, and provides the IP address, port, and so on. Use the NSNetwork, CFNetwork, or BSD sockets API to actually connect to a service over the network.

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