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/*
** broadcaster.c -- a datagram "client" like talker.c, except
** 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>
#include "common.h"
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;
// assemble packet
if (argc < 3 || argc > 4) {
fprintf(stderr,"usage: broadcaster hostname task [message]\n");
exit(1);
}
char buf[MAXBUFLEN],
*task = argv[2],
*message = (argc == 4) ? argv[3] : NULL;
int task_len = strlen(task),
total_len = task_len + 1 + strlen(message);
if (total_len > MAXBUFLEN) {
fprintf(stderr,"payload to long: max %d bytes, was %d\n", MAXBUFLEN, total_len);
exit(1);
}
strcpy(buf, task);
buf[task_len] = 0;
strcpy(buf + 1 + task_len, message);
if ((he=gethostbyname(argv[1])) == NULL) { // get the host info
perror("gethostbyname");
exit(1);
}
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(1);
}
// this call is what allows broadcast packets to be sent:
if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast,
sizeof broadcast) == -1) {
perror("setsockopt (SO_BROADCAST)");
exit(1);
}
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);
if ((numbytes=sendto(sockfd, buf, total_len, 0,
(struct sockaddr *)&their_addr, sizeof their_addr)) == -1) {
perror("sendto");
exit(1);
}
return 0;
}
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