The registered port numbers are the port numbers that companies and other users register with the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the applications that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). In most cases, these applications run as ordinary programs that can be started by nonprivileged users. The registered port numbers are in the range from 1024 through 49151. They follow in sequence the well-known port numbers, which are, in most cases, applications that can only be started by privileged users, such as the Hypertext Transfer Protocol (HTTP) and Post Office Protocol Version 3 (POP3) applications. When one application communicates with another application at another host computer on the Internet, it specifies that application in each data transmission by using its port number.
Examples of applications with registered port numbers include Sun's NEO Object Request Broker (port numbers 1047 and 1048) and Shockwave (port number 1626). Besides the well-known port numbers and the registered port numbers, the remaining ports in the port number spectrum are referred to as dynamic ports or private ports and are numbered from 49152 through 65535.
Before the arrival of ICANN, the port numbers were administered by the Internet Internet Assigned Numbers Authority (IANA).