# WHATPORT(4000)

## NAME

port 4000 — Phoenix / Jekyll dev servers (IANA: Terabase) — A very common local development-server port — Phoenix and Jekyll both default to it — with a long tail of legacy and game traffic behind it.

Protocol: TCP  
IANA: terabase

## DESCRIPTION

IANA registers 4000 as terabase, which you will never meet. What actually binds 4000 today is development tooling: Elixir's Phoenix framework accepts requests on 4000 by default, and `jekyll serve` defaults to 4000 too. Historically the port carried the legacy Mirabilis ICQ client, Diablo II multiplayer, and the RemoteAnything remote-control product, which is why old scanner databases and firewall rulesets attach suspicious labels to it. On a modern host, 4000 is a developer's machine or a container running a dev build far more often than anything else.

## EXPOSURE

**Expose with care.** A framework dev server here has debug pages, stack traces and live reload and must not face the internet; a real application behind a reverse proxy on 4000 is fine.

## CHECK

```sh
curl -sI http://localhost:4000/
```

## SEE ALSO

- docs — [Phoenix — Up and Running ("By default, Phoenix accepts requests on port 4000")](https://phoenix.hexdocs.pm/up_and_running.html) (phoenix.hexdocs.pm)
- docs — [Jekyll — Configuration options (serve port defaults to 4000)](https://jekyllrb.com/docs/configuration/options/) (jekyllrb.com)
- source — [phoenixframework/phoenix on GitHub](https://github.com/phoenixframework/phoenix) (github.com)
- iana — [IANA port registry — 4000 (terabase)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=4000) (iana.org)

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HTML: <https://whatport.net/4000/> · JSON: <https://whatport.net/4000.json> · full dataset: <https://whatport.net/ports.json>