Dns A/AAAA record = IP address
Dns SRV record = IP:port
Not sure why SRV never really caught on for most internet stuff.
(Edit: SRV records are hostnames, not IPs, so I guess it takes two lookups?)
Dns SRV record = IP:port
Not sure why SRV never really caught on for most internet stuff.
(Edit: SRV records are hostnames, not IPs, so I guess it takes two lookups?)
In addition to canonical name & port number they also include priority & weighting values, although the usefulness of these depends on the service.
SRV might not be super visible in the application developer's lane, but swim outside and there's a lot of it about. It's foundational for SIP, for example (IP telephony). Email remains a tremendously significant internet utility and SRV is used, albeit not universally, for discovery of client endpoints (SMTP submission, IMAP, CalDAV etc). However, SRV hasn't replaced MX for SMTP between MTAs, perhaps because MX already does basically the same and was established years prior. And, well, Jabber is dead, but XMPP was another fully worked demonstration of SRV's capability.
In more local environments SRV is used for resolution/discovery in Active Directory (Microsoft) and Bonjour (Apple) - if you listen to the wire on any local network you'll often see a ton of SRV over mDNS or DNS-SD. Perhaps ironically, one of the objections that sometimes arose to using SRV for HTTP was from Active Directory sites with zone cuts at _tcp.example.com and facing additional complexity in any transition.