Winsock Core API – Windows Docs

Overview

The Winsock (Windows Sockets) core API provides the fundamental networking primitives for creating TCP/IP and UDP/IP client and server applications on Windows. It follows the Berkeley sockets API with Windows‑specific extensions.

Key Functions

Function	Description	Header
`WSAStartup`	Initialises the Winsock library.	`winsock2.h`
`WSACleanup`	Terminates use of the Winsock library.	`winsock2.h`
`socket`	Creates a new socket descriptor.	`winsock2.h`
`bind`	Associates a local address with a socket.	`winsock2.h`
`listen`	Marks a socket as a passive listening socket.	`winsock2.h`
`accept`	Accepts an incoming connection request.	`winsock2.h`
`connect`	Establishes a connection to a remote socket.	`winsock2.h`
`send`	Sends data on a connected socket.	`winsock2.h`
`recv`	Receives data from a connected socket.	`winsock2.h`
`sendto`	Sends a datagram to a specific address.	`winsock2.h`
`recvfrom`	Receives a datagram and captures its source address.	`winsock2.h`
`getsockopt`	Retrieves a socket option value.	`winsock2.h`
`setsockopt`	Sets a socket option value.	`winsock2.h`
`closesocket`	Closes an existing socket.	`winsock2.h`
`select`	Monitors multiple sockets for readiness.	`winsock2.h`

Common Structures

Important data structures used with the Winsock API:

sockaddr_in – IPv4 address structure.
sockaddr_in6 – IPv6 address structure.
fd_set – Set of socket descriptors for select.
WSADATA – Holds information about the Windows Sockets implementation.

Typical Initialization Pattern

WSADATA wsaData;
int result = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (result != 0) {
    printf("WSAStartup failed: %d\n", result);
    return 1;
}

/* ... socket operations ... */

WSACleanup();

Reference Links

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