/*
** udp_broadcaster.c -- a UDP sender that broadcasts
**                  this one can broadcast
*/

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

#define SERVERPORT 4950    // the port to send to

int main(int argc, char *argv[])
{
	int sockfd;
	struct sockaddr_in their_addr; // connector's address information
	struct hostent *he;
	int numbytes;
	int broadcast = 1;
	//char broadcast = '1'; // if that doesn't work, try this

	if (argc != 3) {
		fprintf(stderr,"usage: udp_broadcaster hostname message\n");
		exit(1);
	}

	// find the ip address for the server from its dns name
	if ((he=gethostbyname(argv[1])) == NULL) {  // get the host info
		herror("gethostbyname");
		exit(1);
	}
	
	// create the socket
	if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	// this allows sending packets to the broadcast address
	if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
				sizeof broadcast) == -1) {
		perror("setsockopt (SO_BROADCAST)");
		exit(1);
	}

	// fill in info about the server (address to send the packet to)
	their_addr.sin_family = AF_INET;     // host byte order
	their_addr.sin_port = htons(SERVERPORT); // short, network byte order
	their_addr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero);

	// send the string contained in argv[2] ... can send the contents 
	// of a buffer instead
	if ((numbytes=sendto(sockfd, argv[2], strlen(argv[2]), 0,
					(struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
		perror("sendto");
		exit(1);
	}

	printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));

	close(sockfd);

	return 0;
}