# WHATPORT(9503)

## NAME

port 9503 — Unassigned — No IANA assignment and no well-established service — whatever is listening chose the number itself.

Protocol: TCP  
IANA registry

## DESCRIPTION

9503 is unassigned in the IANA service name and port number registry, and Nmap's service database lists it as `unknown` with a very low observed frequency. It sits just above the ports Swoole's documentation uses for its example servers, so it sometimes appears on the same hosts as an extra application listener, but nothing standard claims it. Treat a listener here as an unidentified local application and fingerprint it directly.

## EXPOSURE

**Expose with care.** An unidentified service is an unassessed service. Find out what it is before deciding, and do not assume an obscure port number is protection.

## CHECK

```sh
sudo lsof -nP -iTCP:9503 -sTCP:LISTEN
```

## SEE ALSO

- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/9503/> · JSON: <https://whatport.net/9503.json> · full dataset: <https://whatport.net/ports.json>