3 services carry this tag in their source record. Tags come from the provider, not from us — a tag is a claim about what the service does, not proof that it does it well.
MQTT service discovery (_mqtt._tcp.<domain>): SRV records with priority, weight, port and target host, from Cloudflare DoH. Tells a client where the domain's mqtt service lives without guessing hosts. $0.01 per lookup.
Is TCP port 1883 (MQTT) open on a host? Attempts a connection from Cloudflare's edge and reports open/closed/filtered with the connect time; Cloudflare-fronted hosts are reported as inconclusive because their edge answer...
Change watch for is port 1883 open: runs the check, compares it with the result from your previous call for the same host (kept 90 days) and returns the current answer, changed true/false, the fields that changed with be...