# WHATPORT(33)

## NAME

port 33 — DSP (Display Support Protocol) — Registered to the Display Support Protocol, a service you will effectively never meet.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

IANA registers port 33 as 'dsp — Display Support Protocol', assigned to Ed Cain, on both TCP and UDP. There is no RFC behind the registration and no reference implementation in common use. Nothing on a modern system binds it, so a listener here is almost certainly unrelated software that picked a free low port. Treat the registration as a name in a table, not as a prediction of what you found.

## EXPOSURE

**Expose with care.** The registered protocol is effectively extinct, so whatever answers on 33 is unidentified and should be named before it is exposed.

## CHECK

```sh
nc -vz TARGET 33
```

## 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/33/> · JSON: <https://whatport.net/33.json> · full dataset: <https://whatport.net/ports.json>