The conventional HTTP monitoring port for a NATS server.
nats-server exposes monitoring endpoints — /varz, /connz, /routez, /jsz — over HTTP when you set http_port or pass -m, and 8222 is the conventional choice in NATS' own documentation. It is off until enabled, and it is separate from the client port on 4222. The endpoints are read-only but detailed: server configuration, every connected client, route topology and JetStream state. IANA leaves 8222 unregistered.
Do not expose
The monitoring endpoints have no authentication and enumerate your entire messaging topology; NATS' own hardening guidance is to keep this port off the internet.
$ curl -s --max-time 5 http://TARGET:8222/varzSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.