The dynamic port numbers (also known as the private port numbers) are the port numbers that are available for use by any application to use in communicating with any other application, using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). 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. The port numbers range from 0 through 65535. However, certain port numbers - the well-known port numbers and the registered port numbers - are registered and administered by the Internet Corporation for Assigned Names and Numbers (ICANN) for use by certain classes of applications. The dynamic port numbers are in the highest range, from 49152 through 65535.
Before the arrival of ICANN, the port numbers were administered by the Internet Internet Assigned Numbers Authority (IANA).