non blocking socket check windows

sock_check.cpp

#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
#include <stdio.h>

// Helper function to print Winsock error messages.
void print_wsa_error(const char *msg) {
    int errCode = WSAGetLastError();
    LPVOID errorText = NULL;

    FormatMessageA(
        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        errCode,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPSTR)&errorText,
        0,
        NULL
    );

    if (errorText != NULL) {
        fprintf(stderr, "%s: %s\n", msg, (char *)errorText);
        LocalFree(errorText);
    } else {
        fprintf(stderr, "%s: Unknown error %d\n", msg, errCode);
    }
}

int check_socket_event(SOCKET sock) {
    // Create an event.
    WSAEVENT event = WSACreateEvent();
    if (event == WSA_INVALID_EVENT) {
        print_wsa_error("WSACreateEvent failed");
        return -1;
    }

    // Associate the event with FD_READ, FD_WRITE, and FD_CLOSE notifications.
    if (WSAEventSelect(sock, event, FD_READ | FD_WRITE | FD_CLOSE) == SOCKET_ERROR) {
        print_wsa_error("WSAEventSelect failed");
        WSACloseEvent(event);
        return -1;
    }

    // Perform a non-blocking wait for the event (timeout 0 ms).
    DWORD waitResult = WSAWaitForMultipleEvents(1, &event, FALSE, 0, FALSE);
    if (waitResult == WSA_WAIT_FAILED) {
        print_wsa_error("WSAWaitForMultipleEvents failed");
        WSACloseEvent(event);
        return -1;
    } else if (waitResult == WSA_WAIT_TIMEOUT) {
        printf("No event triggered.\n");
        WSACloseEvent(event);
        return 0;
    }

    // An event has been signaled; retrieve the event details.
    WSANETWORKEVENTS networkEvents;
    if (WSAEnumNetworkEvents(sock, event, &networkEvents) == SOCKET_ERROR) {
        print_wsa_error("WSAEnumNetworkEvents failed");
        WSACloseEvent(event);
        return -1;
    }

    // Print status messages for each event.
    if (networkEvents.lNetworkEvents & FD_READ) {
        printf("Socket is readable.\n");
    }
    if (networkEvents.lNetworkEvents & FD_WRITE) {
        printf("Socket is writable.\n");
    }
    if (networkEvents.lNetworkEvents & FD_CLOSE) {
        printf("Socket is closed.\n");
    }

    int events = networkEvents.lNetworkEvents;
    WSACloseEvent(event);
    return events;
}