/*  multisnd.c - see also diewitherror.c and multirec.c */

/* compile  $ cc -o multisnd.exe multisnd.c diewitherror.c */

/*                   program      multicast ip  port  data          ttl */

/* useage example $ ./multisnd.exe 224.0.22.1 9210 testtesttesttest 2

/* tested with cygwin gcc win32- linux gcc -sun */

 

#include <stdio.h>      /* for fprintf() */

#include <sys/socket.h> /* for socket(), connect(), send(), and recv() */

#include <arpa/inet.h>  /* for sockaddr_in and inet_addr() */

#include <stdlib.h>     /* for atoi() and exit() */

#include <string.h>     /* for memset() */

#include <unistd.h>     /* for sleep() */

 

void DieWithError(char *errorMessage);  /* External error handling function */

 

int main(int argc, char *argv[])

{

    int sock;                         /* Socket */

    struct sockaddr_in multicastAddr; /* Multicast address */

    char *multicastIP;                /* IP Multicast address */

    unsigned short multicastPort;     /* Server port */

    char *sendString;                 /* String to multicast */

    unsigned char multicastTTL;       /* TTL of multicast packets */

    unsigned int sendStringLen;       /* Length of string to multicast */

 

    if ((argc < 4) || (argc > 5))         /* Test for correct number of parameters */

    {

        fprintf(stderr,"Usage:  %s <Multicast Address> <Port> <Send String> [<TTL>]\n",

                 argv[0]);

        exit(1);

    }

 

    multicastIP = argv[1];            /* First arg:  multicast IP address */

    multicastPort = atoi(argv[2]);    /* Second arg:  multicast port */

    sendString = argv[3];             /* Third arg:  String to multicast */

 

    if (argc == 5)                     /* Is TTL specified on command-line? */

        multicastTTL = atoi(argv[4]);  /* Command-line specified TTL */

    else

        multicastTTL = 1;              /* Default TTL = 1 */

 

    /* Create socket for sending/receiving datagrams */

    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)

        DieWithError("socket() failed");

 

    /* Set TTL of multicast packet */

    if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (void *) &multicastTTL,

          sizeof(multicastTTL)) < 0)

        DieWithError("setsockopt() failed");

 

    /* Construct local address structure */

    memset(&multicastAddr, 0, sizeof(multicastAddr));   /* Zero out structure */

    multicastAddr.sin_family = AF_INET;                 /* Internet address family */

    multicastAddr.sin_addr.s_addr = inet_addr(multicastIP);/* Multicast IP address */

    multicastAddr.sin_port = htons(multicastPort);         /* Multicast port */

 

    sendStringLen = strlen(sendString);  /* Find length of sendString */

    for (;;) /* Run forever */

    {

        /* Multicast sendString in datagram to clients every 3 seconds */

        if (sendto(sock, sendString, sendStringLen, 0, (struct sockaddr *)

              &multicastAddr, sizeof(multicastAddr)) != sendStringLen)

            DieWithError("sendto() sent a different number of bytes than expected");

        sleep(3);

    }

    /* NOT REACHED */

}