IETF RFC 6763 section 7.1 (p.21) refers to a CLI program called "dns-sd", which can be used to probe and report zero-config services, records and environments. A number of other web pages also refer to using it in the CLI, but none give a source repo or originating web URL. I don't really want to download a large package containing it, since I only want to probe the dns servers, or to scan the reachable network and get detailed dumps of dns-sd accessible services/directories/?activity when a dns server may or may not be running, not much more, and I can't find a standalone package for it, or even its ultimate upstream source. I can't even be 100% sure what it's capable of, because I can't find its docs either. But it sounds like the right one.
Any ideas how to track such a thing down? And, if they exist, ports for FBSD 11.x and various flavours of Linux (can compile if there is a full Makefile+source). For once, Google hasn't been my friend. Nor has freshports, nor any other search I know.