### ip::multicast::join_group

Socket option to join a multicast group on a specified interface.

    typedef implementation_defined join_group;

Implements the IPPROTO_IP/IP_ADD_MEMBERSHIP socket option.

##### Examples

Setting the option to join a multicast group:

    asio::ip::udp::socket socket(my_context);
    ...
    asio::ip::address multicast_address =
      asio::ip::address::from_string("225.0.0.1");
    asio::ip::multicast::join_group option(multicast_address);
    socket.set_option(option);

##### Requirements

Header: `asio/ip/multicast.hpp`

Convenience header: `asio.hpp`