13-6 SSMからの受信

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

int
main(int argc, char *argv[])
{
  int sock;
  int n;
  int err;
  struct addrinfo hints, *res;
  struct group_source_req gsr;
  char buf[2048];

  if (argc != 2) {
    fprintf(stderr, "usage : %s ssmsrcipv4addr\n", argv[0]);
    return 1;
  }

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET;
  hints.ai_socktype = SOCK_DGRAM;
  hints.ai_flags = AI_PASSIVE;

  err = getaddrinfo(NULL, "12345", &hints, &res);
  if (err != 0) {
    printf("getaddrinfo : %s\n", gai_strerror(err));
    return 1;
  }

  sock = socket(res->ai_family, res->ai_socktype, 0);
  if (sock < 0) {
    perror("socket");
    return 1;
  }

  if (bind(sock, res->ai_addr, res->ai_addrlen) != 0) {
    perror("bind");
    return 1;
  }

  freeaddrinfo(res);

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET;
  hints.ai_socktype = SOCK_DGRAM;

  err = getaddrinfo("232.1.2.3", NULL, &hints, &res);
  if (err != 0) {
    printf("getaddrinfo : %s\n", gai_strerror(err));
    return 1;
  }

  memset(&gsr, 0, sizeof(gsr));
  gsr.gsr_interface = 0; /* any interface */
  memcpy(&gsr.gsr_group, res->ai_addr, res->ai_addrlen);

  freeaddrinfo(res);

  printf("SSM SOURCE : %s\n", argv[1]);

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET;
  hints.ai_socktype = SOCK_DGRAM;

  err = getaddrinfo(argv[1], NULL, &hints, &res);
  if (err != 0) {
    printf("getaddrinfo : %s\n", gai_strerror(err));
    return 1;
  }

  memcpy(&gsr.gsr_source, res->ai_addr, res->ai_addrlen);
  freeaddrinfo(res);

  if (setsockopt( sock, IPPROTO_IP, MCAST_JOIN_SOURCE_GROUP, (void *)&gsr,
                  sizeof(gsr)) != 0) {
    perror("setsockopt");
    return 1;
  }

  n = recv(sock, buf, sizeof(buf), 0);
  if (n < 1) {
    perror("recv");
    return 1;
  }

  printf("%s\n", buf);

  /* (4) */
  if (setsockopt( sock, IPPROTO_IP, MCAST_LEAVE_SOURCE_GROUP, (void *)&gsr,
                  sizeof(gsr)) != 0) {
    perror("setsockopt");
    return 1;
  }

  close(sock);

  return 0;
}

拙著「Linuxネットワークプログラミング」の紹介