multicast - some questions

Hi,
I am sorry for propably stupid question, but i need to write some
multicast application and i have some questions about it:
i think that on reciever side i need to join a group with similar code
to this:
r = setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
(const void *)&mreq, sizeof(mreq));
i suppose that now the kernell sends join group(group membership, igmp
host report)packet, so how can i say which version of igmp the kernell
will use?
and the next question:
after the joining the group does the kernell answers the igmp
membership query from router or i have to do it alone in my code(if i
do so does sb. have some code snipplet)?

thanks
j.
PS: i dont know where to post this message, if sb. knows better place
than this...u know

After joining the multicast group the TCP/IP stack will answer queries
and keep you in the group until you issue a leave. Not sure how to
specify IGMP version.