/* Send Multicast Datagram code example: this program creates a UDP socket and configurue the interface as multicast then send 3 message to 126.1.1.1/4321 

 TO Compile: gcc -g mcastSender.c -o mcastSender
*/ 
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>

struct in_addr localInterface;
struct sockaddr_in groupSock;

int sd,i;

char databuf[1024] = "Sending a Multicast test message .... !";
int datalen = sizeof(databuf);


int main (int argc, char *argv[ ])
{
/* Create a datagram socket on which to send. */
sd = socket(PF_INET, SOCK_DGRAM, 0);
if(sd < 0)
{
  perror("Opening datagram socket error");
  exit(1);
}
else
  printf("Opening the datagram socket...OK.\n");


/* Initialize the group sockaddr structure  */
memset((void *) &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);

/* Disable loopback so you do not receive your own datagrams.
 *
 * {
 *
 * char loopch = 0;
 *
 * if(setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, (char *)&loopch, sizeof(loopch)) < 0)
 *
 * {
 *
 * perror("Setting IP_MULTICAST_LOOP error");
 *
 * close(sd);
 *
 * exit(1);
 *
 * }
 *
 * else
 *
 * printf("Disabling the loopback...OK.\n");
 *
 * }
 *
 * */

/* Set local interface for outbound multicast datagrams. */
/* The IP address specified must be associated with a local, */
/* multicast capable interface. */

//localInterface.s_addr = inet_addr(INADDR_ANY);
localInterface.s_addr = INADDR_ANY;
if(setsockopt(sd, IPPROTO_IP, IP_MULTICAST_IF, (char *)&localInterface, sizeof(localInterface)) < 0)
{
  perror("Setting local interface error");
  exit(1);
}
else
  printf("Setting the local interface...OK\n");
/* Send a message to the multicast group specified by the*/
/* groupSock sockaddr structure. */
/*int datalen = 1024;*/
for (i=1; i <4; ++i)
  if(sendto(sd, databuf, datalen, 0, (struct sockaddr*)&groupSock, sizeof(groupSock)) < 0)
     {perror("Sending datagram message error");}
  else
     printf("Sending datagram message...OK\n");


/* Try the re-read from the socket if the loopback is not disable
 *
 * if(read(sd, databuf, datalen) < 0)
 *
 * {
 *
 * perror("Reading datagram message error\n");
 *
 * close(sd);
 *
 * exit(1);
 *
 * }
 *
 * else
 *
 * {
 *
 * printf("Reading datagram message from client...OK\n");
 *
 * printf("The message is: %s\n", databuf);
 *
 * }
 *
 * */

return 0;
}