code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.netty.server;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.util.AttributeKey;
  import java.util.function.Consumer;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.http.Message;
  
  class WebSocketMessageHandler extends SimpleChannelInboundHandler<Message> {
  
    private final AttributeKey<Consumer<Message>> key;
  
    public WebSocketMessageHandler(AttributeKey<Consumer<Message>> key) {
      this.key = Require.nonNull("Attribute key", key);
    }
  
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Message msg) {
      if (!(ctx.channel().hasAttr(key))) {
        return;
      }
  
      Consumer<Message> handler = ctx.channel().attr(key).get();
  
      ctx.executor()
          .execute(
              () -> {
                try {
                  handler.accept(msg);
                  ctx.flush();
                } catch (Throwable t) {
                  ctx.fireExceptionCaught(t);
                }
              });
    }
  }
  