broadcast_udp.c

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


/* 
   Unless you have a reciver, use tcpdump to view the messages as they leave
   your host.
   sudo tcpdump -n  udp and host 225.0.0.37

*/

#define BYE_OFFICE 12346
#define HELLO_PORT 12345
#define HELLO_GROUP "225.0.0.37"

int main(int argc, char *argv[])
{
    struct sockaddr_in addr;
    struct sockaddr_in addr2;
    int fd;
    int fd2;
    char *message = "Hello, World!";
    char *message2 = "Bye, Office!";

    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        exit(1);
    }

    if ((fd2 = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        exit(1);
    }


    int broadcastEnable=1;
    int ret=setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &broadcastEnable, sizeof(broadcastEnable));
    if (ret<0){
      perror("setsockopt");
      exit(1);
    }
    ret=setsockopt(fd2, SOL_SOCKET, SO_BROADCAST, &broadcastEnable, sizeof(broadcastEnable));
    if (ret<0){
      perror("setsockopt");
      exit(1);
    }
    
    /* set up destination address */
    memset(&addr,0,sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(HELLO_GROUP);
    addr.sin_port=htons(HELLO_PORT);

    memset(&addr2,0,sizeof(addr2));
    addr2.sin_family = AF_INET;
    addr2.sin_addr.s_addr = inet_addr(HELLO_GROUP);
    addr2.sin_port=htons(BYE_OFFICE);

    while (1)
    {
      printf("Sending %s, to %d.\n",message, HELLO_PORT);
      if (sendto(fd, message, strlen(message), 0,(struct sockaddr *) &addr, sizeof(addr)) < 0)
        {
	  perror("sendto");
	  exit(1);
        }
      sleep(3);
      printf("Sending %s, to %d.\n",message, BYE_OFFICE);
      if (sendto(fd2, message2, strlen(message2), 0,(struct sockaddr *) &addr2, sizeof(addr2)) < 0)
        {
	  perror("sendto2");
	  exit(1);
        }
      sleep(3);
    }
}