Winsock is an API that allows Windows software developers to connect their applications to the Internet. It provides a basic set of functions that developers can call on to help their apps communicate with remote computers and send or receive data without writing their own protocol interface.
Originally named "Windows Socket API," Winsock controls the creation of network sockets that direct data to specific applications running on specific computers. It consists of a library of networking functions that developers can use to access basic network protocols, including TCP, UDP, IP, and ICMP (among others). It abstracts most details of establishing connections and transferring data to let the developer focus on other functionality in their application. If necessary, a developer can create raw sockets that allow an application to access other protocols directly.
The Winsock API was developed in 1992 by developers from several software companies (including Microsoft, Novell, 3Com, and Sun Microsystems) to provide a single standard API for Windows networking. Before Winsock, Windows did not have its own networking software stack and instead relied on network software from several vendors, who each provided their own API. This fragmentation made it difficult for developers to create programs that worked on multiple systems. After the release of Winsock as an add-on for Windows 3.1, developers could create network-connected applications that worked on all Windows computers. Every version of Windows since Windows 95 has included the Winsock library.