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

#define PORT   9999          /* Port number       */
#define GROUP "239.0.0.1"    /* Multicast address */

/**
 * Simple multicast server to broadcast the current time.
 */
int main(int argc, char *argv[]) {
	
    struct  sockaddr_in sad;  /* structure to hold server's address */
    int     addrlen;          /* length of address                  */
    int     sd;               /* socket descriptor                  */
    int     sleepDelay;       /* time between sends in seconds      */
    char    buf[50];          /* buffer to hold time                */
    u_char  ttl;              /* time to live option                */

    sleepDelay = 5;           /* 5 seconds */
    
    /* set up socket */
    sd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sd < 0) {
        perror("Error in socket()");
        exit(1);
    }

    
    /* The following code snippet does not contain any multicast specifics   */
    memset((char *)&sad, 0, sizeof(sad));     /* Init memory to zero         */
    sad.sin_family      = AF_INET;            /* Set family to internet      */
    sad.sin_addr.s_addr = htonl(INADDR_ANY);  /* Set the local IP address    */   
    sad.sin_port        = htons(PORT);        /* Set the port number         */
    addrlen             = sizeof(sad);        /* Set the address length      */

     
    /* Set the socket options, in this case set the time to live             *
     * IP_MULTICAST_TTL - Number of intermediate systems through which a     *
     * multicast datagram can be forwarded.                                  */
    ttl = 2;
    if (setsockopt(sd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0) { 
        perror("Error in setsockopt()"); 
        exit(1); 
    }          

    /* Set the multicast address */
    sad.sin_addr.s_addr = inet_addr(GROUP);

    printf("Server Init complete\n");    

    /* Start broadcasting the local time */
    while (1) {
        time_t t = time(0);                              /* get current time */
	sprintf(buf, "Current time: %-24.24s", ctime(&t));  /* make readable */
        printf("Sending message: %s\n", buf);

	/* sendTo is used to send a message to another socket, the socket is *
	 * not required to be in a connected state (unlike send).            */
        if (sendto(sd, buf, sizeof(buf), 0, (struct sockaddr *)&sad, addrlen) < 0) {
 	    perror("Error in sendto()");
	    exit(1);
	}
        sleep(sleepDelay);
    }

    return 0;

}