/* multicast_server.c
 * Adapted from tmouse's IPv6 client/server example code
 * found at http://cboard.cprogramming.com/showthread.php?t=67469
 */

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>

static void DieWithError(const char* errorMessage)
{
	fprintf(stderr, "%s\n", errorMessage);
	exit(1);
}

int main(int argc, char *argv[])
{
	int       sender, listener;	        /* Sockets */
	char*     multicastIP;                  /* Arg: IP Multicast address */
	char*     multicastPort;                /* Arg: Server port */
	char*     token;
	size_t    tokenlen;
	struct    addrinfo *  multicastAddr;     /* Multicast address */
	struct    addrinfo    hints = { 0 };	/* Hints for name lookup */
	struct    timeval timeout = { 0 };

	if (argc != 4)
	{
		fprintf(stderr, "Usage:  %s <Multicast Address> <Port> <Send String>\n", argv[0]);
		exit(1);
	}

	multicastIP   = argv[1];             /* First arg:   multicast IP address */
	multicastPort = argv[2];             /* Second arg:  multicast port */
	token	      = argv[3];
	tokenlen      = strlen(token);

	/* Resolve destination address for multicast datagrams */
	hints.ai_family   = PF_INET6;
	hints.ai_socktype = SOCK_DGRAM;
	hints.ai_flags    = AI_NUMERICHOST;

	if (getaddrinfo(multicastIP, multicastPort, &hints, &multicastAddr) != 0)
	{
		DieWithError("getaddrinfo() failed");
	}

	/* Create socket for sending multicast datagrams */
	if ((sender = socket(multicastAddr->ai_family, multicastAddr->ai_socktype, 0)) == -1) 
	{
		DieWithError("socket() failed");
	}

	/* Create socket for recieving multicast datagrams */
	if ((listener = socket(multicastAddr->ai_family, multicastAddr->ai_socktype, 0)) == -1) 
	{
		DieWithError("socket() failed");
	}

	{
		int hops = 5;
		if (setsockopt(sender, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hops, sizeof(hops)) != 0) 
		{
			DieWithError("setsockopt(MULTICAST_HOPS) failed");
		}
	}

	/* Bind to the multicast port */
	if (bind(listener, multicastAddr->ai_addr, multicastAddr->ai_addrlen) != 0)
	{
		DieWithError("bind() failed");
	}

	/* Join the multicast group.  */
	if ((multicastAddr->ai_family == PF_INET6)&&(multicastAddr->ai_addrlen == sizeof(struct sockaddr_in6)))
	{
		struct sockaddr_in6 *addr = (struct sockaddr_in6 *)(multicastAddr->ai_addr);
		struct ipv6_mreq multicastRequest;  /* Multicast address join structure */

		/* Specify the multicast group */
		memcpy(&multicastRequest.ipv6mr_multiaddr, &(addr)->sin6_addr, sizeof(multicastRequest.ipv6mr_multiaddr));

		/* Accept multicast from any interface */
		multicastRequest.ipv6mr_interface = addr->sin6_scope_id;

		/* Join the multicast address */
		if (setsockopt(listener, IPPROTO_IPV6, IPV6_JOIN_GROUP, (char*) &multicastRequest, sizeof(multicastRequest)) != 0) 
		{
			DieWithError("setsockopt(IPV6_JOIN_GROUP) failed");
		} 
	} else {
		DieWithError("Not IPv6");
	}

	for (;;) /* Run forever */
	{
		int       n;
		int       max_fd;
		fd_set    input;
		
		char      recvString[500];      /* Buffer for received string */
		int       recvStringLen;        /* Length of received string */

		char      sendString[] = "Say Hello\n";
		size_t    sendStringLen = sizeof(sendString)-1;
		char      errorString[] = "That is not correct! Try again!\n";

		struct    sockaddr_in6  from;
		socklen_t fromlen = sizeof(from);
		
		FD_ZERO(&input);
		FD_SET(listener, &input);

		max_fd = listener + 1;

		if (timeout.tv_usec < 100)
		{
			timeout.tv_sec = 1;
			timeout.tv_usec = 0;

			int sendLen = sendto(sender, sendString, sendStringLen, 0, multicastAddr->ai_addr, 
										multicastAddr->ai_addrlen);
			if (sendLen == sendStringLen)
			{
			    printf("Sent [%s] (%i bytes) to %s, port %s\n", sendString, sendLen, 
									multicastIP, multicastPort);
			} else {
			    DieWithError("sendto() sent a different number of bytes than expected");
			}
		}

		n = select(max_fd, &input, NULL, NULL, &timeout);

		/* See if there was an error */
		if (n < 0)
		{
			perror("select failed");
		} else if (n == 0) {
			puts("TIMEOUT");
		} else {
			if (FD_ISSET(listener, &input))
			{
				recvStringLen = recvfrom(listener, recvString, sizeof(recvString) - 1, 0, 
									(struct sockaddr *)&from, &fromlen);
				/* Receive a single datagram from the server */
				if (recvStringLen < 0)
				{
					DieWithError("recvfrom() failed");
				}

				recvString[recvStringLen] = '\0';
				if (strcmp(recvString, "hello")==0) 
				{
					printf("Correct!!\n");
					sendto(listener, token, sizeof(sendString), 0, (struct sockaddr *)&from, 													fromlen);
				} else if (strcmp(recvString, sendString)!=0) {
					sendto(listener, errorString, sizeof(errorString), 0, 									(struct sockaddr *)&from, fromlen);
				}

				/* Print the received string */
				printf("Received string [%s]\n", recvString);
			}
		}
	}

	/* NOT REACHED */
	freeaddrinfo(multicastAddr);
	close(sender);
	close(listener);

	return 0;
}