IP MULTICAST

Hello,

I guess i don't have sufficient informations on how to use ip multicast services.
My API refuse to add me to a multicast group. It fails in the code sample provided below:


memset( &LocalAddr, 0x00, sizeof(LocalAddr));
LocalAddr.sin_family = AF_INET;
LocalAddr.sin_addr.s_addr = inet_addr("192.168.0.1"); //my local machine address
LocalAddr.sin_port = usPort;

err = bind( UDP_Soc, (struct sockaddr *)&LocalAddr, sizeof(LocalAddr));

if (err == SOCKET_ERROR)
return ER_SOCK_BIND;

mreq.imr_multiaddr.s_addr = inet_addr( "233.1.1.1" ); //arbitaral mcast addr
mreq.imr_interface.s_addr = inet_addr( "192.168.0.1" );

if (setsockopt(UDP_Soc, IPPROTO_IP, IP_ADD_MEMBERSHIP,
(char*)&mreq, sizeof(struct ip_mreq)) == SOCKET_ERROR )
return ER_SOCK_BIND; //FAILS HERE!!




This code sample is taken from the tutorials and should work.
My system:
WinNT 4.0
two network interfaces (proxy server SyGate joining LAN with Inet)
TCP/IP installed (this post is a proove)
i dont have any problems with unicast - works both outside and inside my LAN.

please help.
it sais WinNT is multicast compliant.
where do i fail?

thanks in advance
Rem

Maybe one more thing that i've forgot:
setsockopt() returns:
/
WSAENOPROTOOPT The option is unknown or unsupported for the specified provider or socket (see SO_GROUP_PRIORITY limitations).
/

Should i ask my Inet provider on that?
Can i become a router for the IGMP msgs in my LAN?
How do i know if the setsockopt() failure is the network interface fault rather than my code's.

thanks again

Hopefully you started your socket with the Datagram option other wise the errormessage is correct. For there is no multicasting under tcp.
Not under NT at least as far as I know.

Hi,

I'm not sure what is causing your error, but I have a couple of projects which illustrate the required steps for creating a multicast server and the client. I can't remember where I got them and there's no details of the author on the files so use them however you see fit ;)


Lee.