port number

Definition of port number in The Network Encyclopedia.

What is Port Number (in computer networking)?

A 16-bit integer assigned to a port on a TCP/IP host that enables the host to communicate with another host on the network. Ports can have numbers between 0 and 65,536 and are divided into two types:

  • Well-known port numbers, which are fixed numbers between 0 and 1023 and are assigned by the Internet Assigned Numbers Authority (IANA). Some of these numbers are currently unassigned or reserved for future use.
  • Dynamically assigned port numbers, which the operating system assigns as needed when a TCP/IP application or service requests a port. These numbers are between 1024 and 65,536 and can be released and reassigned as needed.

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ports are different, but TCP and UDP ports use the same assigned port numbers for a given TCP/IP application or service whenever possible.

See also: