11.2 How to Use Filters
Whenever the application wishes to use a multicast IP address, for either
sending or receiving, a filter is needed. The application can establish this through
setting the IP_ADD_MEMBERSHIP
option for the required socket
accompanied by the multicast address that the application wants to use. If subsequently
the host wants to stop receiving the multicast stream, set the
IP_DROP_MEMBERSHIP
option for the required socket accompanied with
the multicast address.
Adding or removing a multicast address filter causes the WINC chip firmware to add/remove both MAC layer filter and IP layer filter in order to pass or prevent messages from reaching to the host.