9
discard
TCP and UDP · 0x0009
Port 9 — discard
Others
Port 9 carries Discard over TCP and UDP. Being at or below 1023, only root may open it on Unix.
0–1023. On Unix only root may open one.
Where it sits in 65535
A port number is 16 bits, so it stops at 65535. The narrow band at the left is everything up to 1023.
065535
- Service
- Discard (discard)
- Kind
- Others
- Protocol
- TCP and UDP
- Range
- Well-known
- Root needed
- Yes
- Hexadecimal
- 0x0009
- Binary
- 0000000000001001
- Two bytes
- 0 · 9
Same kind
Time, printing, play — the ones that fit nowhere else.
Ports next to it
How to read this
- A port number is 16 bits, so it runs 0 to 65535. There is no port 65536.
- Opening anything at or below 1023 needs root on Unix.
- Plain and encrypted often live on different numbers — 80 and 443, for one.
- Numbers like 3000 and 8080 were never registered; those are marked as custom.
Frequently asked questions
Q. What is port 9 used for?
Discard (discard) uses it, over both TCP and UDP.
Q. Does opening port 9 need root?
Yes. It is at or below 1023, so on Unix only root may open it.
Q. Which range does port 9 fall in?
Well-known (0–1023). In hex it is 0x0009.
Q. Does port 9 have a twin?
Not a separate one. It either was encrypted from the start or negotiates TLS on the same number.