Thread: [help need] IPv6 multicast in winsock2?

I'm writing a simple piece of code to let the client to be able to receive multicast UDPs to link-local all-node "ff02::1". But I encountered the following problem. Any comments?

I'm under Windows XP SP2. According to msdn IPPROTO_IPV6 page, it should be
supported by this OS. But the "setsockopt" line of code gives 10022(WSAEINVAL: The level parameter is not valid, or the information in optval parameter is not valid.)

IPV6_MREQ imr;
TCHAR *all_nodes = L"ff02::1";
//get IPv6 multicast address from string
if ( WSAStringToAddress(all_nodes, AF_INET6, NULL, (struct sockaddr *)&sin, &len) == SOCKET_ERROR)
{
...... //break out
}

//set option to join link-local all-nodes multicast group
imr.ipv6mr_interface = 0;
imr.ipv6mr_multiaddr = sin.sin6_addr; //all_nodes;

if (::setsockopt(m_sockBCastV6, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, (char *)&imr, sizeof(imr)) == SOCKET_ERROR)
{
...... //break out
}

I also tried other options at IPPROTO_IPV6, and the only option that didn't
give 10022 error is IPV6_MULTICAST_IF.

I'm using Visual C++ in Visual Studio 2005. And OS is Windows XP, SP2.

Any help would be highly appreciated!

I'm not sure what the problem is (your code looks alright, have you made sure that you have IPv6 installed?) but you may wish to take a look at the IPv6 multicast example code thread.

I don't know why it should work like this. But switching the order of setsockopt and bind solves the problem.