sub _new_client {
    my $sock = $main_socket->accept();
    my $conn = bless {
        'sock' =>  $sock,
        'state' => 'connected'
    }, $g_pkg;             #< different CLASSNAME
    my $rcvd_notification_proc =
        &$g_login_proc ($conn, $sock->peerhost(), $sock->peerport());
    if ($rcvd_notification_proc) {
        $conn->{rcvd_notification_proc} = $rcvd_notification_proc;
        my $callback = sub {_rcv($conn,0)};
        set_event_handler ($sock, "read" => $callback);
    } else {  # Login failed
        $conn->disconnect();
    }
}