my $sslSocket = IO::Socket::SSL->new(
    Listen             => 5,
    LocalPort          => XXX,
    Proto              => 'tcp',
    SSL_startHandshake => 0,
    SSL_cert_file      => 'XXX',
    SSL_key_file       => 'XXX',
  ) or die "failed to listen: $!";

  my $server = Net::Async::WebSocket::Server->new(
    on_client => sub {
      my ( undef, $client ) = @_;

      $client->configure(
        on_text_frame => sub {
          my ( $self, $frame ) = @_;

          $self->send_text_frame( $frame );
        },
      );
    },
    on_handshake => sub {
      my ( $self, $client, $hs, $continue ) = @_;

      $continue->( 1 );
    }
  );

  my $loop = IO::Async::Loop->new;
  $loop->add( $server );

  $server->listen(
    handle => $sslSocket
  )->get;