A registered port is numbered from 1024 through 49151. A protocol can register a port with IANA to reduce conflicts, so different protocols do not use the same number. section 22.1.1
Keep the three port ranges distinct:
- Well-known ports: 0–1023; IANA controls these for common protocols. section 22.1.1
- Registered ports: 1024–49151; protocols may register them with IANA and they are also called user ports. section 22.1.1
- Ephemeral ports: 49152–65535; clients commonly select these dynamically as source ports. section 22.1.1
Why registration matters
An enterprise developing a protocol can register a port in the registered range with IANA. Registration helps prevent another protocol from selecting the same port, while a client may use an ephemeral source port for its connection. section 22.1.1
