【多播】编写UDP代码，可以接受224.0.0.2组内消息

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
int main(int argc, char const *argv[])
{
    // 1.创建套接字
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
    {
        perror("sockfd");
        return -1;
    }
    // 2.多播
    struct ip_mreq mul;
    mul.imr_multiaddr.s_addr = inet_addr("224.0.0.2");
    mul.imr_interface.s_addr = htonl(INADDR_ANY);
    setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void *)&mul, sizeof(mul));
    // 3.绑定
    struct sockaddr_in myaddr;
    myaddr.sin_family = AF_INET;
    myaddr.sin_port = htons(8000);
    myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    int ret = 0;
    ret = bind(sockfd, (struct sockaddr *)&myaddr, sizeof(myaddr));
    if (ret != 0)
    {
        perror("bind");
        return -1;
    }
    // 4.接受数据
    char buf[1500] = "";
    char ip[16] = "";
    unsigned short port = 0;
    struct sockaddr_in srcaddr;
    socklen_t len = sizeof(srcaddr);
    while (1)
    {
        bzero(buf, sizeof(buf));
        bzero(&srcaddr, len);
        recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)&srcaddr, &len);
        inet_ntop(AF_INET, (void *)&srcaddr.sin_addr, ip, 16);
        port = ntohs(srcaddr.sin_port);
        printf("%s/%hu:%s\n", ip, port, buf);
    }
    // 5.关闭套接字
    close(sockfd);
    return 0;
}