WinSock

In short: Windows Sockets API — the standard interface on Windows through which applications open sockets and handle network communication.

In more detail: WinSock translates the BSD socket API from the Unix world for Windows and provides it to developers as a DLL. Practically every network-capable Windows application uses WinSock directly or indirectly (via the libraries of higher-level programming languages).

In Depth

WinSock (officially the “Windows Sockets API”) came about because Windows originally had no built-in network subsystem compatible with the BSD socket API established in the Unix world — various vendors initially implemented incompatible solutions of their own, until the industry agreed on a common WinSock standard. Since then, developers have been able to use an API that is conceptually very similar to the BSD socket API (socket(), bind(), connect(), send(), recv()), but adapted to Windows-specific peculiarities.

In practice, very few developers today program directly against the raw WinSock API — modern programming languages (Python, JavaScript/Node.js, .NET) provide their own, more convenient network APIs that only use WinSock internally as the lowest implementation layer. Nevertheless, WinSock remains the fundamental basis on which practically every Windows network application is ultimately built, similar to the role the BSD socket API plays on Linux/macOS.

See also: Sockets