The Sockets, in the context of network programming, are the software endpoints that represent one side of a two-way communication link between two programs running on a network. A socket provides an application programming interface (API) for sending and receiving data over a network, abstracting away the complex details of the underlying protocols like TCP/IP.
The most common socket implementation for Windows is called Winsock (Windows Sockets API). To establish a network connection, a server application will create a socket, bind it to a specific IP address and port number on the server, and then listen for incoming connection requests. A client application will create its own socket and then attempt to connect to the server's IP address and port number. Once the connection is established (a process known as the TCP three-way handshake), both the client and server can use their respective sockets to send and receive streams of data as if they were simply reading from and writing to a local file. This socket-based communication is the foundation for almost all internet applications, including web browsers, FTP clients, and email.
It is also the mechanism used to communicate with LXI-compliant programmable power supplies over a LAN. The control program on the PC acts as the client, and the power supply acts as the server, listening for incoming connections on a specific port.