/* 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 */
}
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