# WHATPORT(6666)

## NAME

port 6666 — IRC (alternate) — One of the five IRC ports in IANA's 6665-6669 ircu range — an alternate to 6667.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA assigns 6665-6669/tcp as a single block named ircu, after the Undernet IRC daemon, and RFC 7194 confirms plaintext IRC is covered by that assignment. Most networks listen on all five so clients have a fallback when one is blocked, and 6666 is the most commonly offered alternate. Its memorable digits also made it a long-standing favourite for command-and-control channels of IRC-controlled bots, which is why some corporate filters block the whole range outright.

## EXPOSURE

**Expose with care.** Plaintext IRC — nick, credentials sent to services, and every message travel unencrypted. Prefer 6697 with TLS (RFC 7194) for anything you care about.

## CHECK

```sh
printf 'QUIT\r\n' | nc -v TARGET 6666
```

## SEE ALSO

- spec — [RFC 7194 — Default Port for Internet Relay Chat (IRC) via TLS/SSL](https://www.rfc-editor.org/rfc/rfc7194.html) (rfc-editor.org)
- iana — [IANA Service Name and Transport Protocol Port Number Registry — 6665-6669 (ircu)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=6666) (iana.org)
- source — [ircu2 — Undernet IRC Daemon](https://github.com/UndernetIRC/ircu2) (github.com)

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HTML: <https://whatport.net/6666/> · JSON: <https://whatport.net/6666.json> · full dataset: <https://whatport.net/ports.json>