sub send_msg {
        my ( $self, $mac, $ucp_method, $arg_ref ) = @_;
        $arg_ref = {} unless ref($arg_ref) eq 'HASH';

        croak('Must specify ucp_method') if !defined $ucp_method;

        my $encoded_mac;

        # use MAC_ZERO for discovery packets
        # Otherwise MAC must be specified
        if (   ( $ucp_method eq UCP_METHOD_DISCOVER )
            or ( $ucp_method eq UCP_METHOD_ADV_DISCOVER ) )
        {
            $encoded_mac = MAC_ZERO;
        }
        else {
            croak(
'Must specify mac address for $ucp_method_name->{$ucp_method} packets'
            ) if !defined $mac;
            $encoded_mac = encode_mac($mac);
        }

        my $msg_args = {
            ucp_method  => $ucp_method,
            dst_mac     => $encoded_mac,
            data_to_get => $arg_ref->{data_to_get},
            data_to_set => $arg_ref->{data_to_set},
        };

        $msg_args->{src_ip} = $arg_ref->{src_ip} if $arg_ref->{src_ip};

        my $msg_ref;
        eval { $msg_ref = Net::UDAP::MessageOut->new($msg_args) } or do {
            carp($@);
            return;
        };
        my $sock = $self->socket;
        $sock->sockopt( SO_BROADCAST, 1 );
        my $dest_ip = inet_ntoa(INADDR_BROADCAST);
        my $dest = pack_sockaddr_in( PORT_UDAP, INADDR_BROADCAST );
        log(    info => '*** Broadcasting '
              . $ucp_method_name->{$ucp_method}
              . ' message to MAC address '
              . decode_mac($encoded_mac)
              . " on $dest_ip\n" );
        return $sock->send( $msg_ref->packed, 0, $dest );
    }