139
netbios-ssn
TCP · 0x008B
Port 139 — netbios-ssn
Files
Port 139 carries NetBIOS session 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
- NetBIOS session (netbios-ssn)
- Kind
- Files
- Protocol
- TCP
- Range
- Well-known
- Root needed
- Yes
- Hexadecimal
- 0x008B
- Binary
- 0000000010001011
- Two bytes
- 0 · 139
Same kind
Moving files about, or sharing a disk.
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 139 used for?
NetBIOS session (netbios-ssn) uses it, over TCP.
Q. Does opening port 139 need root?
Yes. It is at or below 1023, so on Unix only root may open it.
Q. Which range does port 139 fall in?
Well-known (0–1023). In hex it is 0x008B.
Q. Does port 139 have a twin?
Not a separate one. It either was encrypted from the start or negotiates TLS on the same number.