# WHATPORT(6699)

## NAME

port 6699 — reserved (peer-to-peer file sharing, historically) — Reserved at IANA on TCP; remembered as the Napster and WinMX file-sharing port.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA marks 6699/tcp as Reserved with no assignee, while 6699/udp was registered in 2020 for the Babel routing protocol over DTLS (RFC 8968). The TCP side is famous for something else entirely: nmap's service table still names it napster, from the era when Napster-style and WinMX clients defaulted to this port for peer connections. Those networks are gone, so an open 6699/tcp today is either a long-abandoned client or unrelated software on a free port.

## EXPOSURE

**Expose with care.** A live listener here is worth investigating — either an unmaintained file-sharing client or something you have not identified. It is not a service you should be deliberately publishing.

## CHECK

```sh
sudo lsof -nP -iTCP:6699 -sTCP:LISTEN
```

## SEE ALSO

- iana — [IANA Service Name and Transport Protocol Port Number Registry — 6699](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=6699) (iana.org)
- spec — [RFC 8968 — Babel Routing Protocol over Datagram Transport Layer Security](https://www.rfc-editor.org/rfc/rfc8968.html) (rfc-editor.org)
- source — [nmap-services (Nmap's port/service frequency database)](https://github.com/nmap/nmap/blob/master/nmap-services) (github.com)

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HTML: <https://whatport.net/6699/> · JSON: <https://whatport.net/6699.json> · full dataset: <https://whatport.net/ports.json>