Subject: multicast
From: [email-masked] ("Bruce D. McLeod")

19 Mar 1997 21:24:34 -0800
Approved: [email-masked]
Distribution: cygnus
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This seems to be due to the mapping of IP_ADD_MEMBERSHIP to 35
in cygwin32/socket.h as opposed to 5 in winsock.h.  I hardcoded
the option at 5, and it works fine.

Bruce

>Date: Wed, 19 Mar 1997 11:16:14 -0500
>To: [email-masked]
>From: "Bruce D. McLeod" <[email-masked]>
>Subject: multicast
>
>Has anyone successfully used multicast using the sys/sockets.h version
>of the network stuff?  I am getting "This option is unsupported"
>for the setsockopt:
>
>      err = setsockopt( gListener, IPPROTO_IP, IP_ADD_MEMBERSHIP,
>                        (char *) &multiStruct, sizeof(multiStruct) );
>
>Bruce
>
>The full code...
>
>
>#include <sys/socket.h>
>#include <netinet/in.h>
>#include <netdb.h>
>#include <stdio.h>
>
>#define PANIC() printf("panic\n"); exit(1);
>#define ASSERT( x ) if ( (x) == 0 ) { PANIC(); }
>
>const static int gMyPort = 5500;
>const static char* gMyMultiIp = "225.1.1.88";
>int gListener;
>
>main( int argc, char **argv )
>{
>   if (argc > 1) {
>      struct sockaddr_in localAddr;
>      int err, value;
>      struct ip_mreq multiStruct;
>      char hostName[200];
>      struct hostent* myHostent;
>
>      // Set up listening socket.
>      gListener = socket( AF_INET, SOCK_DGRAM, 0 );
>      ASSERT( gListener != -1 );
>
>      value = 1;
>      err = setsockopt( gListener, SOL_SOCKET, SO_REUSEADDR,
>                        (char *) &value, sizeof(value) );
>      ASSERT( err != -1 );
>
>      err = gethostname( hostName, 200 );
>      ASSERT( err != -1 );
>      myHostent = gethostbyname( hostName );
>      ASSERT( myHostent != NULL );
>
>      localAddr.sin_family = AF_INET;
>      localAddr.sin_addr.s_addr = *((long *) myHostent->h_addr_list[0]);
>      localAddr.sin_port = htons( gMyPort );
>
>      err = bind( gListener, (struct sockaddr *) &localAddr,
sizeof(localAddr) );
>      ASSERT( err != -1 );
>
>      multiStruct.imr_multiaddr.s_addr = inet_addr( gMyMultiIp );
>      multiStruct.imr_interface.s_addr = *((long *) myHostent->h_addr_list[0]);
>      err = setsockopt( gListener, IPPROTO_IP, IP_ADD_MEMBERSHIP,
>                        (char *) &multiStruct, sizeof(multiStruct) );
>      if (err == -1) perror("setsockopt failed");
>      ASSERT( err != -1 );
>
>      for (;;) {
>         static const int bufsize = 200;
>         char buf[bufsize];
>         struct sockaddr fromAddr;
>         int fromAddrLen, bytes;
>
>         printf( "MultiTest: waiting for data\n" );
>
>         fromAddrLen = sizeof(fromAddr);
>         bytes = recvfrom( gListener, buf, bufsize, 0,
>                           &fromAddr, &fromAddrLen );
>         ASSERT( bytes >= 0 );
>
>         if (bytes == 0) {
>            printf( "MultiTest: disconnect received\n" );
>            close( gListener );
>            return 1;
>         }
>
>         printf( "MultiTest: msg received: %s\n", buf );
>      }
>   } else {
>      static const char msg[] = "Hello world.";
>      struct sockaddr_in remoteAddr;
>      int bytes;
>
>      int s = socket( AF_INET, SOCK_DGRAM, 0 );
>      ASSERT( s != -1 );
>
>      remoteAddr.sin_family = AF_INET;
>      remoteAddr.sin_port = htons( gMyPort );
>      remoteAddr.sin_addr.s_addr = inet_addr( gMyMultiIp );
>
>      bytes = sendto( s, msg, strlen( msg ) + 1, 0,
>                      (struct sockaddr *) &remoteAddr, sizeof(remoteAddr) );
>      ASSERT( bytes == (int) strlen( msg ) + 1 );
>      printf("MultiTest: msg sent\n");
>
>      close( s );
>   }
>
>   return 0;
>}
>

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