Leaving a Multicast Group.

When a process is no longer interested in a multicast group, it informs the kernel that it wants to leave that group. It is important to understand that this doesnt mean that the kernel will no longer accept multicast datagrams destined to that multicast group. It will still do so if there are more precesses who issued a "multicast join" petition for that group and are still interested. In that case the hostremains member of the group, until all the processes decide to leave the group.Even more: if you leave the group, but remain bound to the port you were receiving the multicast traffic on, and there are more processes that joined the group, you will still receive the multicast transmissions.The idea is that joining a multicast group only tells the IP and data link layer (which in some cases explicitly tells the hardware) to accept multicast datagrams destined to that group. It is not a per-process membership, but a per-host membership.