# WHATPORT(3333)

## NAME

port 3333 — dec-notes (in practice: OpenOCD GDB, mining stratum, alt HTTP) — Registered to DEC Notes; today it is OpenOCD's GDB server, mining-pool endpoints, and any app that liked the repeating digits.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA registers 3333 as `dec-notes`, Digital's VAX Notes conferencing system, which nobody has run in decades. The repeating digits made the port a popular default elsewhere: OpenOCD serves its GDB remote-debug connection on 3333 by default (telnet on 4444, Tcl on 6666), cryptocurrency mining pools very commonly publish Stratum endpoints on 3333, and countless applications pick it as an alternate HTTP port. Nothing about 3333 tells you which of these you have hit, so the banner decides.

## EXPOSURE

**Expose with care.** Depends entirely on what is listening: an OpenOCD GDB server is unauthenticated debug control of a device and must stay on localhost, while a pool endpoint is public by design.

## CHECK

```sh
nc -v TARGET 3333
```

## SEE ALSO

- docs — [OpenOCD User's Guide — GDB and OpenOCD](https://openocd.org/doc/html/GDB-and-OpenOCD.html) (openocd.org)
- source — [OpenOCD source repository](https://github.com/openocd-org/openocd) (github.com)
- 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/3333/> · JSON: <https://whatport.net/3333.json> · full dataset: <https://whatport.net/ports.json>