543
klogin
TCP · 0x021F
Port 543 — klogin
Authentication
Port 543 carries Kerberos login over TCP. 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
- Kerberos login (klogin)
- Kind
- Authentication
- Protocol
- TCP
- Range
- Well-known
- Root needed
- Yes
- Hexadecimal
- 0x021F
- Binary
- 0000001000011111
- Two bytes
- 2 · 31
Same kind
Checking who you are and handing out keys.
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 543 used for?
Kerberos login (klogin) uses it, over TCP.
Q. Does opening port 543 need root?
Yes. It is at or below 1023, so on Unix only root may open it.
Q. Which range does port 543 fall in?
Well-known (0–1023). In hex it is 0x021F.
Q. Does port 543 have a twin?
Not a separate one. It either was encrypted from the start or negotiates TLS on the same number.