组播数据发送与接收示例代码

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <errno.h>


static int log_debug;

#define MSGBUFSIZE 256

static void usage(void)
{
    printf("Usage: mcast [option] [argv]\n");
    printf("    -v : verbose\n");
    printf("    -h : help\n");
    printf("    -c : client say hello to group\n");
    printf("    -s : listener recveive from group\n");
    printf("    -g [group]: ip group for client and server\n");
    printf("    -p [port] : ip port for client and server\n");
}

static int add_multigroup(int fd, char *group)
{
    struct ip_mreq mreq;
    
    memset((void*)&mreq, 0, sizeof(mreq));
    mreq.imr_multiaddr.s_addr = inet_addr(group);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
                   &mreq, sizeof(mreq)) < 0) {
        perror("setsockopt:IP_ADD_MEMBERSHIP");
        return -1;
    }
    
    return 0;
}

static int start_client(char *group, int port)
{
    int fd, ret;
    struct sockaddr_in addr;
    char *message = "Hello, World!";
    
    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket");
        return -1;
    }
    
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(group);
    addr.sin_port = htons(port);
    
    while (1) {
        if (sendto(fd, message, strlen(message), 0,
                   (struct sockaddr *) &addr, sizeof(addr)) < 0) {
            perror("sendto");
            ret = -1;
            break;
        }
        
        sleep(1);
    }
    
    close(fd);
    
    return ret;
}

static int start_server(char *group, int port)
{
    int fd = -1;
    struct sockaddr_in addr;
    int nbytes = 0;
    socklen_t addrlen = sizeof(struct sockaddr_in);
    char msgbuf[MSGBUFSIZE];
    u_int reuseflag = 1;
    int ret = 0;
    
    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket");
        return -1;
    }
    
    ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuseflag, sizeof(reuseflag));
    if (ret < 0) {
        perror("SO_REUSEADDR");
        close(fd);
        return -1;
    }
    
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(port);
    
    if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("bind");
        close(fd);
        return -1;
    }
    
    ret = add_multigroup(fd, group);
    if (ret) {
        printf("join a multicast group %s failed!\n", group);
        close(fd);
        return ret;
    }
    
    while (1) {
        nbytes = recvfrom(fd, msgbuf, MSGBUFSIZE, 0,
                          (struct sockaddr *)&addr, (socklen_t *)&addrlen);
        if (nbytes < 0) {
            perror("recvfrom");
            ret = -1;
            break;
        }
        
        msgbuf[nbytes] = '\0';
        
        printf("recv: %s\n", msgbuf);
    }
    
    close(fd);
    
    return ret;
}

int main(int argc, char *argv[])
{
    int ret = 0;
    int c;
    int mode = 0;
    int port = -1;
    char *group = NULL;
    
    while (1) {
        int option_index = 0;
        static struct option long_options[] = {
            {"help",  no_argument,          0, 'h' },
            {"verbose", no_argument,        0, 'v' },
            {"client",  no_argument,        0, 'c' },
            {"server",  no_argument,        0, 's' },
            {"group",   required_argument,  0, 'g' },
            {"port",    required_argument,  0, 'p' },
            {    0,             0,          0,  0  }
        };
        
        c = getopt_long(argc, argv, "hvcsg:p:",
                        long_options, &option_index);
        if (c == -1)
            break;
        
        switch (c) {
            case 'v':
                log_debug = 1;
                break;
                
            case 'c':
                mode = 0;
                break;
                
            case 's':
                mode = 1;
                break;
                
            case 'g':
                group = optarg;
                break;
                
            case 'p':
                port = atoi(optarg);
                break;
                
            case 'h':
                usage();
                return 0;
                
            default:
                break;
        }
    }
    
    if (port < 0 || !group) {
        usage();
        return -1;
    }
    
    switch (mode) {
        case 0:
            printf("multicast test:client..\n");
            ret = start_client(group, port);
            break;
        case 1:
            printf("multicast test:server..\n");
            ret = start_server(group, port);
            break;
        default:
            break;
    }
    
    return ret;
}