# WHATPORT(6)

## NAME

port 6 — Unassigned — Unassigned at IANA — no registered service, no common squatter.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

IANA lists port 6 as Unassigned on both TCP and UDP. It has no assignee, no reference document, and no daemon that binds it as a default. The number is easy to confuse with IP protocol number 6, which is TCP itself, but that is a different registry entirely. A listener here is bespoke, and identifying the owning process is the only reliable step.

## EXPOSURE

**Expose with care.** Unregistered, so an open port 6 tells you nothing on its own; name the process before judging exposure.

## CHECK

```sh
sudo lsof -nP -iTCP:6 -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/6/> · JSON: <https://whatport.net/6.json> · full dataset: <https://whatport.net/ports.json>