# WHATPORT(9)

## NAME

port 9 — Discard — Discard — a black hole that accepts everything you send and replies with nothing.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

RFC 863 defines Discard as a service that reads and throws away all data with no response, on TCP and UDP alike. It was built as a throughput and sink test for network stacks, and it shipped alongside echo, daytime and chargen as an inetd built-in. It is disabled by default on modern systems. Port 9 is also the conventional destination for Wake-on-LAN magic packets over UDP, which is why WoL tooling references it even though no discard server is involved.

## EXPOSURE

**Expose with care.** Harmless in content since it never replies, but it is an unnecessary listener; there is no reason to expose it deliberately.

## CHECK

```sh
printf 'sink this\n' | nc -v TARGET 9
```

## SEE ALSO

- spec — [RFC 863 — Discard Protocol](https://www.rfc-editor.org/rfc/rfc863.html) (rfc-editor.org)
- 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/9/> · JSON: <https://whatport.net/9.json> · full dataset: <https://whatport.net/ports.json>