Discard — a black hole that accepts everything you send and replies with nothing.
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.
Expose with care
Harmless in content since it never replies, but it is an unnecessary listener; there is no reason to expose it deliberately.
$ printf 'sink this\n' | nc -v TARGET 9Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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