Overview

The following list of port numbers comprises information derived mainly from RFC 1700. Any errors or omissions are, therefore, my own. The port numbers are divided into three ranges, as follows:

• Well-known ports are those from 0 through 1,023.

• Registered ports are those from 1,024 through 49,151.

• Dynamic and/or private ports are those from 49,152 through 65,535.

The list provided here is not exhaustive. For a complete up-to-date list of port assignments see the IANA URL: URL = ftp://ftp.isi.edu/in-notes/iana/assignments/port-numbers.

A.1 Well-known port numbers

Ports are used in protocols such as TCP and UDP to identify the end points of logical connections that carry long-term conversations. For many applications it is useful to have the service port predefined, so that clients connecting to a server know what port to connect to for widely used applications such as FTP, Telnet, DNS, and so on. These ports are sometimes called well-known ports or assigned ports. These ports are controlled and assigned by the IANA, and on most systems can be used only by system (or root) processes or by programs executed by privileged users. The assigned ports take only a small part of the available port space, for many years restricted to the range 0 255. Recently, the range has been expanded by the IANA to 0 1,023.