#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <arpa/inet.h>

#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <errno.h>

int main(int argc, const char **argv)
{
	int udp_sock = socket(AF_INET, SOCK_DGRAM, 0);
	struct sockaddr_in local_addr, peer_addr;
	const int sock_bool = 1;
	socklen_t ip_len = sizeof(struct sockaddr_in);
	const size_t MAX_MSG = 1024;
	uint8_t message[MAX_MSG];
	int res = 0;

	/*
	 * bind to some arbitrary UDP port on localhost
	 */
	memset(&local_addr, 0, sizeof(struct sockaddr_in));
	local_addr.sin_family = AF_INET;
	local_addr.sin_port = 0;

	// listen on the localhost for broadcasts
	if( inet_aton("127.0.0.1", &local_addr.sin_addr) == 0 )
	{
		printf("Failed to set addr\n");
		return 1;
	}

	/*
	 * setup he broadcast target address
	 */
	
	memset(&peer_addr, 0, sizeof(struct sockaddr_in));
	peer_addr.sin_family = AF_INET;
	// fixed port number for broadcasting
	peer_addr.sin_port = htons(30451);
	if( inet_aton("127.255.255.255", &peer_addr.sin_addr) == 0 )
	{
		printf("Failed to set broadcast addr\n");
		return 1;
	}

	/*
	 * setup the socket
	 */
	
	if( setsockopt(udp_sock, SOL_SOCKET, SO_BROADCAST, &sock_bool, sizeof(sock_bool)) != 0 )
	{
		printf("Failed to set broadcast option\n");
		return 1;
	}
	
	if( bind(udp_sock, (struct sockaddr*)&local_addr, sizeof(local_addr)) != 0 )
	{
		printf("Failed to bind to addr\n");
		return 1;
	}

	if( getsockname( udp_sock, (struct sockaddr*)&local_addr, &ip_len) != 0 )
	{
		printf("Failed to get sockname\n");
		return 1;
	}

	printf("Bound to %s:%d for replies\n",
		inet_ntoa(local_addr.sin_addr),
		local_addr.sin_port
	);

	/* send some arbitrary data */
	if( sendto( udp_sock, message, 17, 0, (struct sockaddr*)&peer_addr, ip_len ) == -1 )
	{
		perror("Failed to send broadcast");
		return 1;
	}

	printf("Sent broadcast to %s:%d\n",
		inet_ntoa(peer_addr.sin_addr),
		local_addr.sin_port
	);

	while ( 1 )
	{
		res = recvfrom( udp_sock, message, MAX_MSG, 0, (struct sockaddr*)&peer_addr, &ip_len );

		if( res == -1 )
		{
			printf("Failed to receive message\n");
			return 1;
		}

		if( ip_len != sizeof(struct sockaddr_in) )
		{
			printf("Wrong addr len\n");
			return 1;
		}

		printf("Received broadcast reply of %d bytes from %s:%d\n",
			res,
			inet_ntoa(peer_addr.sin_addr),
			peer_addr.sin_port
		);

		/*
		 * ignore actual message content
		 */
	}
}