137
netbios-ns
UDP · 0x0089
Port 137 — netbios-ns
Name lookup
Port 137 carries NetBIOS name service over 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
- NetBIOS name service (netbios-ns)
- Kind
- Name lookup
- Protocol
- UDP
- Range
- Well-known
- Root needed
- Yes
- Hexadecimal
- 0x0089
- Binary
- 0000000010001001
- Two bytes
- 0 · 137
Same kind
Turning names into addresses, or looking people and machines up.
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 137 used for?
NetBIOS name service (netbios-ns) uses it, over UDP.
Q. Does opening port 137 need root?
Yes. It is at or below 1023, so on Unix only root may open it.
Q. Which range does port 137 fall in?
Well-known (0–1023). In hex it is 0x0089.
Q. Does port 137 have a twin?
Not a separate one. It either was encrypted from the start or negotiates TLS on the same number.