MSDN Documentation

Winsock API Reference

This section provides comprehensive documentation for the Windows Sockets API (Winsock), which enables applications to communicate over a network using the TCP/IP protocol suite and other network protocols.

Introduction to Winsock

Winsock is a C-language API that provides a standardized interface for network programming on Windows. It allows developers to create client and server applications that can communicate with each other across local networks or the internet.

Key Concepts

• Sockets: Endpoints for network communication.
• Protocols: TCP (reliable, connection-oriented) and UDP (unreliable, connectionless).
• Address Families: AF_INET for IPv4, AF_INET6 for IPv6.
• Data Structures: `sockaddr`, `sockaddr_in`, `WSADATA`.

Core Functions

The Winsock API consists of a set of functions that cover various networking operations. Here are some of the most commonly used functions:

Initialization and Cleanup

• WSAStartup: Initializes the Winsock DLL.
• WSACleanup: Shuts down Winsock usage.

Socket Management

• socket: Creates a socket.
• bind: Associates a local address with a socket.
• connect: Establishes a connection to a remote host.
• listen: Puts a socket into a listening state.
• accept: Accepts an incoming connection.
• closesocket: Closes a socket.

Data Transfer

• send: Sends data over a socket.
• recv: Receives data from a socket.
• sendto: Sends data to a specific address.
• recvfrom: Receives data from any address.

Error Handling

Winsock functions return specific error codes that can be interpreted using WSAGetLastError.

int iResult = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (iResult == INVALID_SOCKET) {
    int errorCode = WSAGetLastError();
    // Handle error, e.g., outputting errorCode
    printf("Socket creation failed with error: %d\n", errorCode);
}
            

Advanced Topics

• Asynchronous I/O (Overlapped I/O)
• Socket Options
• Name Resolution (DNS)