A port number is a 16-bit number that identifies a specific process running on a computer. Applications use port numbers to communicate with each other over a network.
Port numbers are typically assigned by the Internet Assigned Numbers Authority (IANA). However, some port numbers are reserved for specific services, such as port 80 for HTTP.
Port numbers are used in conjunction with IP addresses to identify a network application uniquely. The IP address specifies the computer on the network, and the port number identifies the program on that computer.