On computer and telecommunication devices, a port is generally a specific physical connection to some other devices, usually with a socket and plug of some kind. Typically, a personal computer is provided with one or more serial ports and one parallel port. The serial port supports sequential, one bit-at-a-time transmission to peripheral devices such as scanners and the parallel port supports multiple-bit-at-a-time transmission to devices such as printers.
In programming, a port is a "logical connecting place" and specifically, the protocols of the Transport Layer of the Internet Protocol Suite(like TCP/UDP) uses a numerical identifier of the endpoints for host-to-host communications. Such an endpoint is known as a port and the identifier is the port number.
Higher-level applications that use TCP/IP such as the Web protocol, Hypertext Transfer Protocol, have ports with preassigned numbers. These are known as "well-known ports" that have been assigned by the Internet Assigned Numbers Authority (IANA). Other application processes are given port numbers dynamically for each connection. When a service (server program) initially is started, it is said to bind to its designated port number. As any client program wants to use that server, it also must request to bind to the designated port number. Port numbers are from 0 to 65535.
Ports 0 to 1024 are reserved for use by certain privileged services. For the HTTP service, port 80 is defined as a default and it does not have to be specified in the Uniform Resource Locator (URL).
Ports 1024 to 49151 are registered ports 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).
Ports 49151 to 65535 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.Before the arrival of ICANN, the port numbers were administered by the Internet Internet Assigned Numbers Authority (IANA).
Official: Port/application combination is registered with IANA .
Unofficial: Port/application combination is not registered with IANA.
Conflict Port: is in use for multiple applications.
If you want to know the port number for a specific web service (program), look here: