winsocket 加入组播 代码

以下是使用Winsock加入组播的示例代码：

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

#define MCAST_ADDR "239.0.0.1"  // 组播地址
#define MCAST_PORT 8888        // 组播端口

int main()
{
    // 初始化Winsock
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed with error: %d\n", WSAGetLastError());
        return 1;
    }

    // 创建套接字
    SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock == INVALID_SOCKET) {
        printf("socket failed with error: %d\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    // 设置套接字为允许发送组播数据
    int ttl = 1;
    if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (const char*)&ttl, sizeof(ttl)) != 0) {
        printf("setsockopt IP_MULTICAST_TTL failed with error: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 加入组播组
    struct ip_mreq mreq;
    mreq.imr_multiaddr.s_addr = inet_addr(MCAST_ADDR);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (const char*)&mreq, sizeof(mreq)) != 0) {
        printf("setsockopt IP_ADD_MEMBERSHIP failed with error: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 绑定套接字到本地地址和端口
    struct sockaddr_in local_addr;
    local_addr.sin_family = AF_INET;
    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    local_addr.sin_port = htons(MCAST_PORT);
    if (bind(sock, (struct sockaddr*)&local_addr, sizeof(local_addr)) != 0) {
        printf("bind failed with error: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 接收组播数据
    struct sockaddr_in from_addr;
    char buf[1024];
    while (1) {
        int from_len = sizeof(from_addr);
        int ret = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr*)&from_addr, &from_len);
        if (ret > 0) {
            buf[ret] = '\0';
            printf("Received: %s\n", buf);
        }
    }

    // 关闭套接字并清理Winsock
    closesocket(sock);
    WSACleanup();

    return 0;
}

在上面的代码中，首先初始化Winsock，创建一个UDP套接字，并将其设置为允许发送组播数据。然后，使用IP_ADD_MEMBERSHIP选项将套接字加入组播组，并绑定到本地地址和端口。最后，使用recvfrom函数接收组播数据。注意，在实际使用中，你需要根据实际情况修改组播地址、端口和接收数据的方式。