101
hostname
TCP · 0x0065
Port 101 — hostname
Name lookup
Port 101 carries NIC Host Name Server 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
- NIC Host Name Server (hostname)
- Kind
- Name lookup
- Protocol
- TCP
- Range
- Well-known
- Root needed
- Yes
- Hexadecimal
- 0x0065
- Binary
- 0000000001100101
- Two bytes
- 0 · 101
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 101 used for?
NIC Host Name Server (hostname) uses it, over TCP.
Q. Does opening port 101 need root?
Yes. It is at or below 1023, so on Unix only root may open it.
Q. Which range does port 101 fall in?
Well-known (0–1023). In hex it is 0x0065.
Q. Does port 101 have a twin?
Not a separate one. It either was encrypted from the start or negotiates TLS on the same number.