What is "socket"

A network socket (in English: network socket) is an end point of a communication flow between processes through a computer network. Nowadays, most communication between computers is based on the Internet Protocol (IP). However most network sockets are Internet sockets.

A socket API (API sockets) is an application programming interface (API), usually provided by the operating system, which allows application programs to control and use network sockets. Internet socket Apis are usually based on the default Berkeley sockets.

A socket address (socket address) is the combination of an IP address and a port number, much like the end of a phone connection which is the combination of a phone number and a certain extension. Based on this address, internet sockets deliver incoming data packets to the process or thread of appropriate application.

Source: Wikipedia