multicast example

#include
#include
#include
#include
#include
#include
#include
 
struct in_addr localInterface;
struct sockaddr_in groupSock;
int sd;

int main (int argc, char **argv)
{
 char databuf[1024] = "1111111111111111111111111111";
 int datalen = strlen(databuf);

 if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
 {
    perror("Opening datagram socket error");
    exit(1);
 }

 
 /* Initialize the group sockaddr structure with a */
 /* group address of 226.1.1.1 and port 4321. */
 memset((char *) &groupSock, 0, sizeof(groupSock));
 groupSock.sin_family = AF_INET;
 groupSock.sin_addr.s_addr = inet_addr("226.1.1.1");
 groupSock.sin_port = htons(4321);

 /* Send a message to the multicast group specified by the*/
 /* groupSock sockaddr structure. */
 if(sendto(sd, databuf, datalen, 0, (struct sockaddr*)&groupSock, sizeof(groupSock)) < 0)
 {
  perror("Sending datagram message error");
 }
 else
    printf("Sending datagram message...OK\n");

 return 0;
}

================================================================

#include
#include
#include
#include
#include
#include
#include

struct sockaddr_in localSock;
struct ip_mreq group;
int sd;
int datalen;
char databuf[1024];

int main(int argc, char *argv[])
{
 /* Create a datagram socket on which to receive. */
 if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
 {
  perror("Opening datagram socket error");
  exit(1);
 }

 /* Bind to the proper port number with the IP address */
 /* specified as INADDR_ANY. */
 memset((char *)&localSock, '\0', sizeof(localSock));
 localSock.sin_family = AF_INET;
 localSock.sin_port = htons(4321);
 localSock.sin_addr.s_addr = htonl(INADDR_ANY);
 if(bind(sd, (struct sockaddr*)&localSock, sizeof(localSock)))
 {
  perror("Binding datagram socket error");
  close(sd);
  exit(1);
 }

 /* Join the multicast group 226.1.1.1 on the local 203.106.93.94 */
 /* interface. Note that this IP_ADD_MEMBERSHIP option must be */
 /* called for each local interface over which the multicast */
 /* datagrams are to be received. */
 group.imr_multiaddr.s_addr = inet_addr("226.1.1.1");
 group.imr_interface.s_addr = htonl(INADDR_ANY);
 if(setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&group, sizeof(group)) < 0)
 {
  perror("Adding multicast group error");
  close(sd);
  exit(1);
 }

 /* Read from the socket. */
 datalen = sizeof(databuf);
 if(read(sd, databuf, datalen) < 0)
 {
  perror("Reading datagram message error");
  close(sd);
  exit(1);
 }
 else
  printf("The message from multicast client is: %s\n", databuf);

 return 0;
}