1. #include "net.h"
    3. int main (void)
    4. {
    6.     int fd = -1;
    7.     struct sockaddr_in sin;
    9.     /* 1. 创建socket fd */
    10.     if ((fd = socket (AF_INET, SOCK_DGRAM, 0)) < 0) {    //udp程序
    11.         perror ("socket");
    12.         exit (1);
    13.     }
    15.     /* 2. 允许绑定地址快速重用 */
    16.     int b_reuse = 1;
    17.     setsockopt (fd, SOL_SOCKET, SO_REUSEADDR, &b_reuse, sizeof (int));
    19.     /*加入多播组*/
    20.     struct ip_mreq mreq;
    21.     bzero(&mreq, sizeof(mreq));
    22.     mreq.imr_multiaddr.s_addr = inet_addr("235.10.10.3");
    23.     mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    25.     setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq));
    27.     /*2. 绑定 */
    28.     /*2.1 填充struct sockaddr_in结构体变量 */
    29.     bzero (&sin, sizeof (sin));
    30.     sin.sin_family = AF_INET;
    31.     sin.sin_port = htons (SERV_PORT);    //网络字节序的端口号
    33.     /* 让服务器程序能绑定在任意的IP上 */
    34. #if 1
    35.     sin.sin_addr.s_addr = htonl (INADDR_ANY);
    36. #else
    37.     if (inet_pton (AF_INET, SERV_IP_ADDR, (void *) &sin.sin_addr) != 1) {
    38.         perror ("inet_pton");
    39.         exit (1);
    40.     }
    41. #endif
    42.     /*2.2 绑定 */
    43.     if (bind (fd, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
    44.         perror ("bind");
    45.         exit (1);
    46.     }
    48.     char buf[BUFSIZ];
    49.     struct sockaddr_in cin;
    50.     socklen_t addrlen = sizeof (cin);
    51.     printf ("\nmulticast demo started!\n");
    52.     while (1) {
    53.         bzero (buf, BUFSIZ);
    54.         if (recvfrom (fd, buf, BUFSIZ - 1, 0, (struct sockaddr *) &cin, &addrlen) < 0) {
    55.             perror ("recvfrom");
    56.             continue;
    57.         }
    59.         char ipv4_addr[16];
    60.         if (!inet_ntop (AF_INET, (void *) &cin.sin_addr, ipv4_addr, sizeof (cin))) {
    61.             perror ("inet_ntop");
    62.             exit (1);
    63.         }
    65.         printf ("Recived from(%s:%d), data:%s", ipv4_addr, ntohs (cin.sin_port), buf);
    67.         if (!strncasecmp (buf, QUIT_STR, strlen (QUIT_STR))) {    //用户输入了quit字符
    68.             printf ("Client(%s:%d) is exiting!\n", ipv4_addr, ntohs (cin.sin_port));
    69.         }
    71.     }
    73.     close (fd);
    75.     return 0;
    76. }