# WHATPORT(7)

## NAME

port 7 — Echo — Echo — the server sends back every byte you send it, one of the original inetd debugging services.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

Echo is defined in RFC 862: over TCP the server returns the stream unchanged until the client closes, and over UDP it returns each datagram to its sender. It exists as a reachability and round-trip test from the era before ping and traceroute were universal, and it shipped as an inetd or xinetd built-in on classic UNIX. Modern distributions ship it disabled. Its UDP form is a documented reflection and amplification vector, because a spoofed source address gets an equal-sized reply sent to the victim.

## EXPOSURE

**Do not expose.** The UDP form is a spoofable reflector documented in CISA's amplification-attack alert, and the service has no legitimate internet-facing use.

## CHECK

```sh
printf 'hello\n' | nc -v TARGET 7
```

## SEE ALSO

- spec — [RFC 862 — Echo Protocol](https://www.rfc-editor.org/rfc/rfc862.html) (rfc-editor.org)
- docs — [CISA Alert — UDP-Based Amplification Attacks](https://www.cisa.gov/news-events/alerts/2014/01/17/udp-based-amplification-attacks) (cisa.gov)
- 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/7/> · JSON: <https://whatport.net/7.json> · full dataset: <https://whatport.net/ports.json>