windows 设置组播程序 设置接受组播 win32 socket 代码例子

以下是一个基本的Winsock程序，可以接收组播数据包：

#include <Winsock2.h>
#include <iostream>
using namespace std;

#define MULTICAST_IP "239.255.255.255"
#define MULTICAST_PORT 12345

int main()
{
    // 初始化Winsock
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0) {
        cout << "WSAStartup failed: " << iResult << endl;
        return 1;
    }

    // 创建套接字
    SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock == INVALID_SOCKET) {
        cout << "socket failed: " << WSAGetLastError() << endl;
        WSACleanup();
        return 1;
    }

    // 启用广播
    int optval = 1;
    iResult = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char*)&optval, sizeof(optval));
    if (iResult == SOCKET_ERROR) {
        cout << "setsockopt for broadcast failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 设置组播地址和端口
    struct sockaddr_in groupAddr;
    groupAddr.sin_family = AF_INET;
    groupAddr.sin_addr.s_addr = inet_addr(MULTICAST_IP);
    groupAddr.sin_port = htons(MULTICAST_PORT);

    // 绑定套接字到组播地址和端口
    iResult = bind(sock, (struct sockaddr*)&groupAddr, sizeof(groupAddr));
    if (iResult == SOCKET_ERROR) {
        cout << "bind failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 接收数据
    char buf[1024];
    struct sockaddr_in senderAddr;
    int senderAddrSize = sizeof(senderAddr);
    while (true) {
        iResult = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr*)&senderAddr, &senderAddrSize);
        if (iResult == SOCKET_ERROR) {
            cout << "recvfrom failed: " << WSAGetLastError() << endl;
            closesocket(sock);
            WSACleanup();
            return 1;
        }
        cout << "Received data: " << buf << endl;
    }

    // 关闭套接字和Winsock
    closesocket(sock);
    WSACleanup();

    return 0;
}

在以上代码中，我们通过 `setsockopt` 函数启用了广播功能，并将套接字绑定到组播地址和端口。然后，我们使用 `recvfrom` 函数来接收组播数据包。注意，在接收数据时，我们还需要获取发送方的地址和端口信息，这可以通过 `recvfrom` 函数的最后两个参数实现。