/* multirec.c - see also diewitherror.c and
multisnd.c */
/*
compile $ cc -o multirec.exe multirec.c
diewitherror.c */
/* program multicast ip port */
/*
useage example $ ./multirec.exe 224.0.22.1 9210 */
/*
tested with cygwin gcc win32- linux gcc -sun */
#include
<stdio.h> /* for printf() and
fprintf() */
#include
<sys/socket.h> /* for socket(), connect(), sendto(), and recvfrom() */
#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 close() */
#include
<time.h> /* modified for timestamps */
#define
MAXRECVSTRING 255 /* Longest string to
receive */
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; /* Port */
char recvString[MAXRECVSTRING+1]; /*
Buffer for received string */
int recvStringLen; /* Length of received string
*/
struct ip_mreq multicastRequest; /* Multicast address join structure */
if (argc != 3) /* Test for correct number of arguments */
{
fprintf(stderr,"Usage: %s
<Multicast IP> <Multicast Port>\n", argv[0]);
exit(1);
}
multicastIP = argv[1]; /* First arg: Multicast IP address
(dotted quad) */
multicastPort = atoi(argv[2]);/* Second
arg: Multicast port */
/* Create a best-effort datagram socket
using UDP */
if ((sock = socket(PF_INET, SOCK_DGRAM,
IPPROTO_UDP)) < 0)
DieWithError("socket() failed");
/* Construct bind structure */
memset(&multicastAddr, 0,
sizeof(multicastAddr)); /* Zero out
structure */
multicastAddr.sin_family = AF_INET; /* Internet address family */
multicastAddr.sin_addr.s_addr =
htonl(INADDR_ANY); /* Any incoming
interface */
multicastAddr.sin_port =
htons(multicastPort); /* Multicast
port */
/* Bind to the multicast port */
if (bind(sock, (struct sockaddr *)
&multicastAddr, sizeof(multicastAddr)) < 0)
DieWithError("bind()
failed");
/* Specify the multicast group */
multicastRequest.imr_multiaddr.s_addr =
inet_addr(multicastIP);
/* Accept multicast from any interface */
multicastRequest.imr_interface.s_addr =
htonl(INADDR_ANY);
/* Join the multicast address */
if (setsockopt(sock, IPPROTO_IP,
IP_ADD_MEMBERSHIP, (void *) &multicastRequest,
sizeof(multicastRequest)) < 0)
DieWithError("setsockopt()
failed");
/* Receive a single datagram from the
server */
/* Start loop here */
int c;
int x1
= 1000000; /* initialize loop variables */
int x2
= 0;
while
(x2 < x1)
{
/* x1++
*/
/*
uncomment the line above to have a limit */
if
((recvStringLen = recvfrom(sock, recvString, MAXRECVSTRING, 0, NULL, 0)) <
0)
DieWithError("recvfrom()
failed");
recvString[recvStringLen] = '\0';
time_t
tim=time(NULL); /* get time stamp to
print with recieved data */
char *s=ctime(&tim);
s[strlen(s)-1]=0;
// remove \n
/*
printf("it is %s now.\n", s); */
printf("Time Received: %s :
%s\n", s, recvString); /* Print
the received string */
}
close(sock);
exit(0);
} /*
main */
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