#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

/*
    CpSc 824 -- SIMPLE datagram multicast example...

    This program multicasts a outMessageBuf to multicast address:

         229.8.2.4 and port 5824 (both arbitrarily chosen)

    and waits for replies from whatever machines receive it...

*/

/* The "available" multicast addresses are 225.0.0.0 through
   238.255.255.255. */
#define MULTICASTADDR "229.8.2.4"
#define PORTNUMBER 5824

main (argc, argv) 
int argc;
char *argv[];
{
    int socketDesc;    /* Socket Descriptor */
    int addrLength;
    struct sockaddr_in destinationAddr, 
                       myAddr, 
                       responseAddr;
    struct hostent *hostNameBufPtr;
    char outMessageBuf[128];
    char inMessageBuf[128];
    struct timeval timeOut;
    fd_set readReadySet;
    int msgCount;
    char limitLanFlag = 0x1;

    /* Create socket from which to send */
    if ((socketDesc = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("open error on socket");
        exit(1);
    }

    /* BIND the socket on our end to any available port (i.e.
       leave it up to the system to assign a port (used for
       replys */
    myAddr.sin_family = AF_INET;
    myAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    myAddr.sin_port = htons(0);    /* The zero says bind to any port */
    if (bind(socketDesc, (struct sockaddr *) &myAddr, sizeof(myAddr)) 
        < 0) {
        perror("bind error");
        exit(1);
    }
    
    /* And build MULTICAST address */
    destinationAddr.sin_family = AF_INET;
    destinationAddr.sin_addr.s_addr = htonl(inet_addr(MULTICASTADDR));
    destinationAddr.sin_port = htons(PORTNUMBER);

    /* Set the socket to permit multicasts on the local LAN */
    if (setsockopt(socketDesc, IPPROTO_IP, IP_MULTICAST_TTL, &limitLanFlag, 
                   sizeof(limitLanFlag)) != 0) {
        perror("setsockopt error");
        exit(1);
    }
        
    /* Broadcast message */
    strcpy(outMessageBuf, "Hello world");
    if (sendto(socketDesc, outMessageBuf, strlen(outMessageBuf)+1, 0, 
        (struct sockaddr *)&destinationAddr, sizeof(destinationAddr)) < 0) {
        perror("socket send error");
        exit(1);
    }

    /* And wait for up to 5 seconds for replys to come back */
    /* Set timeOut value for receive to 5 seconds */
    timeOut.tv_sec = 5L;
    timeOut.tv_usec = 0L;

    /* Read responses from hosts accepting the multicast until a read 
       finally times-out. */
    FD_ZERO(&readReadySet);
    FD_SET(socketDesc,&readReadySet);
    msgCount = 0;
    while (select(socketDesc+1,&readReadySet, NULL, NULL, &timeOut) > 0) {
        addrLength= sizeof(responseAddr);
        if (recvfrom(socketDesc,inMessageBuf,sizeof(inMessageBuf),0,
                     &responseAddr, &addrLength) < 0) {
            perror("socket read error");
            exit(1);
        }

        /* Convert the address of the responding machine to its symbolic
           format */
        if ((hostNameBufPtr=gethostbyaddr(&responseAddr.sin_addr.s_addr,
            sizeof(responseAddr.sin_addr.s_addr), AF_INET)) == NULL) {
            perror("gethostbyaddr error");
        }
        else {
            printf("Message received from %s\n", hostNameBufPtr->h_name);
        }
        printf("Received Message=%s\n\n",inMessageBuf);
        msgCount++;
        FD_SET(socketDesc,&readReadySet);
    }

    printf("Received %d messages\n",msgCount);

}