Network socket

A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node. Because of the standardization of the TCP/IP protocols in the development of the Internet, the term network socket is most commonly used in the context of the Internet protocol suite, and is therefore often also referred to as Internet socket. In this context, a socket is externally identified to other hosts by its socket address, which is the triad of transport protocol, IP address, and port number. The term socket is also used for the software endpoint of node-internal inter-process communication (IPC), which often uses the same API as a network socket. The use of the term socket in software is analogous to the function of an electrical female connector, a device in hardware for communication between nodes interconnected with an electrical cable. Similarly, the term port is used for external physical endpoints at a node or device. The application programming interface (API) for the network protocol stack creates a handle for each socket created by an application, commonly referred to as a socket descriptor. In Unix-like operating systems, this descriptor is a type of . It is stored by the application process for use with every read and write operation on the communication channel. At the time of creation with the API, a network socket is bound to the combination of a type of network protocol to be used for transmissions, a network address of the host, and a port number. Ports are numbered resources that represent another type of software structure of the node. They are used as service types, and, once created by a process, serve as an externally (from the network) addressable location component, so that other hosts may establish connections.