DNSServiceResolve

DNSServiceResolve is a function in the DNS-SD (Bonjour) API that resolves a discovered service instance to its connection parameters. After a DNSServiceBrowse call finds a service, DNSServiceResolve is used to obtain the host name and port where the service is available, along with the TXT record that carries metadata about the service.

Usage typically follows a browse operation. You initiate DNSServiceBrowse to list services of a given type, and for each discovered service instance you call DNSServiceResolve with the serviceName, regType, and domain. The resolution is asynchronous and results are delivered via a callback, commonly declared as DNSServiceResolveReply.

In the DNSServiceResolveReply callback, you receive the interfaceIndex, an errorCode, the full service name (fullname), the host target (hosttarget), the port, and the TXT record data (txtRecord with length txtLen). A successful resolve provides the hosttarget and port that identify where to connect to the service. The TXT record contains textual metadata describing the service, encoded as a sequence of key=value strings.

After obtaining hosttarget, you typically perform a separate address lookup (for example using DNSServiceGetAddrInfo) to resolve the host to IP addresses for a connection. Note that the port is provided in network byte order and should be converted to host byte order before use. The hosttarget may be a hostname requiring DNS resolution, and the TXT record should be parsed according to the service’s documented schema.

DNSServiceResolve requires maintaining the DNSServiceRef for ongoing asynchronous operations and releasing it when finished. It is commonly used in conjunction with DNSServiceBrowse and DNSServiceGetAddrInfo within the DNS-SD framework. See also: DNSServiceBrowse, DNSServiceGetAddrInfo, DNS-SD.