Make sure you bind to multicast address in the
receiver
program. Only time you need to specify interface
address in the receiver is during filling up
mr.imr_interface.s_addr. After making these changes
you should be able to see the packets. Also I am not
sure if you need to "connect". So you might comment
that out too.
-pkd
--- Matias Freytes <[EMAIL PROTECTED]>
wrote:
> Hello,
> As you'll notice I'm new to this. I want to
> read/write to/from
> multicast adresses. I've followed the examples from
> Multicast-HOWTO, but I
> must be missing something. I'm sending/receiving
> from the same host (don't
> have access to another one yet) and I've tried LOOP
> on and LOOP off. There
> are no assertion fails, but the receiver never gets
> anything.
> These are the send and receive routines:
>
>
> SEND routine
>
----------------------------------------------------------
> #include <assert.h>
> #include <stdio.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
>
> int main(void)
> { struct sockaddr_in da, la;
> int ss;
> unsigned char loop = 1, ttl=1;
> int r;
>
> da.sin_family = AF_INET;
> da.sin_port = htons (5004);
> r = inet_aton ("224.168.1.1", &(da.sin_addr));
> assert (r>=0);
>
> la.sin_family = AF_INET;
> la.sin_port = htons (5004);
> r = inet_aton ("192.168.1.1", &(la.sin_addr));
> assert (r>=0);
>
> /* send configuration */
> ss = socket(AF_INET, SOCK_DGRAM, 0);
> assert (ss>=0);
> r = connect (ss, (struct sockaddr*)&da,
> sizeof(da));
> assert (r>=0);
> r = setsockopt (ss, IPPROTO_IP, IP_MULTICAST_LOOP,
> &loop, sizeof(loop));
> assert (r>=0);
> r = setsockopt (ss, IPPROTO_IP, IP_MULTICAST_TTL,
> &ttl, sizeof(ttl));
> assert (r>=0);
> r = setsockopt (ss, IPPROTO_IP, IP_MULTICAST_IF,
> &(la.sin_addr),
> sizeof(la.sin_addr));
> assert (r>=0);
>
> send (ss, "Msg one\0", 8, 0);
> send (ss, "Msg two\0", 8, 0);
> send (ss, "Msg three\0", 10, 0);
> send (ss, "Msg four\0", 9, 0);
> send (ss, "Msg five\0", 9, 0);
>
> close (ss);
> return (0);
> }
>
-------------------------------------------------------------
>
>
=*=*=*=*=*=*=*=*=*==*=*=*=*=*=*=*=*=*=*==*=*=*==*=*=*=*=*=*=*=*==*
>
> RECEIVE routine
>
--------------------------------------------------------------
> #include <assert.h>
>
> #include <stdio.h>
> #include <sys/socket.h>
> #include <sys/types.h>
> #include <netinet/in.h>
>
> int main(void)
> { struct sockaddr_in da, la;
> struct ip_mreq mr;
> int rs, r, n;
> unsigned char msg[100];
>
> da.sin_family = AF_INET;
> da.sin_port = htons (5004);
> r = inet_aton ("224.168.1.1", &(da.sin_addr));
> assert (r>=0);
>
> la.sin_family = AF_INET;
> la.sin_port = htons (5004);
> r = inet_aton ("192.168.1.1", &(la.sin_addr));
> assert (r>=0);
>
> /* recv configuration */
> rs = socket(AF_INET, SOCK_DGRAM, 0);
> assert (rs>=0);
> r = bind (rs, (struct sockaddr*)&la, sizeof(la));
> assert (r>=0);
> r = connect (rs, (struct sockaddr*)&da,
> sizeof(da));
> assert (r>=0);
> mr.imr_multiaddr.s_addr = da.sin_addr.s_addr;
> mr.imr_interface.s_addr = la.sin_addr.s_addr;
> r = setsockopt (rs, IPPROTO_IP, IP_ADD_MEMBERSHIP,
> &mr, sizeof(mr));
> assert (r>=0);
>
> n = 0;
> while (n<4) {
> r = recv (rs, msg, 100, 0);
> printf ("MSG: %s\n", msg);
> n++;
> }
> }
>
>
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
> I run the receive routine, switch to another
> terminal and run the send
> routine. Send routine finishes, but receive routine
> never get anything.
> Any hints?
>
> Thank you.
>
> --------------
> Matias Freytes
> Laboratorio de Comunicaciones Digitales
> Universidad Nacional de Cordoba
> Argentina
>
>
> -
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>
>
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