The CFNetServices API is part of Bonjour, Apple’s implementation of zero-configuration networking (ZEROCONF). The CFNetServices API 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. Applications can use the CFNetServices API to discover the services that are available on the network and to find all access information — such as name, IP address, and port number — needed to use each service.
In effect, Bonjour registration and discovery combine the functions of a local DNS server and AppleTalk, allowing applications to provide the kind of user-friendly browsing available in the AppleTalk Chooser using open protocols, such as Multicast DNS (mDNS). Bonjour gives applications easy access to services over local IP networks without requiring the service to support an AppleTalk stack, and without requiring a DNS server on the local network.
For a full description of Bonjour, see Bonjour Overview.