code: @RequestHandler(patterns = "/ws/echo", priority = 100)
      public void onGet(Request.In.Get event, IOSubchannel channel)
              throws InterruptedException {
          final HttpRequest request = event.httpRequest();
          if (!request.findField(
              HttpField.UPGRADE, Converters.STRING_LIST)
              .map(f -> f.value().containsIgnoreCase("websocket"))
              .orElse(false)) {
              return;
          }
          openChannels.add(channel);
          channel.respond(new ProtocolSwitchAccepted(event, "websocket"));
          event.stop();
      }
docs: Handle `GET` requests.
  
  @param event the event
  @param channel the channel
  @throws InterruptedException the interrupted exception