Registers @socket to receive multicast messages sent to @group.
@socket must be a %G_SOCKET_TYPE_DATAGRAM socket, and must have
been bound to an appropriate interface and port with
g_socket_bind().
If @iface is %NULL, the system will automatically pick an interface
to bind to based on @group.
If @source_specific is %TRUE, source-specific multicast as defined
in RFC 4604 is used. Note that on older platforms this may fail
with a %G_IO_ERROR_NOT_SUPPORTED error.
Registers @socket to receive multicast messages sent to @group. @socket must be a %G_SOCKET_TYPE_DATAGRAM socket, and must have been bound to an appropriate interface and port with g_socket_bind().
If @iface is %NULL, the system will automatically pick an interface to bind to based on @group.
If @source_specific is %TRUE, source-specific multicast as defined in RFC 4604 is used. Note that on older platforms this may fail with a %G_IO_ERROR_NOT_SUPPORTED error.