keepalive => sub {
      my ( $io_wheel_id, $kernel, $heap ) = @_[ ARG0, KERNEL ];
      return unless exists $heap->{clients}{$io_wheel_id};
      $heap->{clients}{$io_wheel_id}->put("keepalive");
      $kernel->delay( 'keepalive' => 10, $io_wheel_id );
  },