WSAStartup

Syntax

Parameters

Return Value

Remarks

An application must successfully call WSAStartup before it can use any other functions in the Winsock DLL. A successful call to WSAStartup must be matched by a corresponding call to WSACleanup.

The wVersionRequested parameter is used by the application to specify the Winsock version it requires. The Winsock DLL checks if it can support the requested version. If the DLL supports the requested version or a higher version, it initializes itself for the highest minor version supported that is less than or equal to the requested minor version.

After a successful call to WSAStartup, the application can use the information returned in the WSADATA structure to determine the Winsock implementation details.

If the Winsock DLL cannot support the version requested by the application, WSAStartup returns an error code indicating this failure.

It is important to note that the Winsock DLL is initialized on a per-process basis. Multiple threads within the same process can call WSAStartup, but this does not result in multiple initializations. The Winsock DLL keeps an internal count of how many times WSAStartup has been called. Each successful call to WSAStartup must be balanced by a call to WSACleanup.

Example

#include <winsock2.h>
#include <stdio.h>

int main() {
    WSADATA wsaData;
    int iResult;

    // Make sure to use version 2.2 or higher
    const WORD wVersionRequested = MAKEWORD(2, 2);

    // Initialize Winsock
    iResult = WSAStartup(wVersionRequested, &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    printf("Winsock initialized successfully!\n");
    printf("Winsock version: %d.%d\n", LOBYTE(wsaData.wVersion), HIBYTE(wsaData.wVersion));
    printf("Description: %s\n", wsaData.szDescription);

    // ... perform Winsock operations ...

    // Clean up Winsock
    WSACleanup();
    printf("Winsock cleaned up.\n");

    return 0;
}

Requirements