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   /*
    * Copyright 2019 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.example.mqtt.heartBeat;
  
  import io.netty.bootstrap.Bootstrap;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelInitializer;
  import io.netty.channel.EventLoopGroup;
  import io.netty.channel.nio.NioEventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.socket.nio.NioSocketChannel;
  import io.netty.handler.codec.mqtt.MqttDecoder;
  import io.netty.handler.codec.mqtt.MqttEncoder;
  import io.netty.handler.timeout.IdleStateHandler;
  
  import java.util.concurrent.TimeUnit;
  
  public final class MqttHeartBeatClient {
      private MqttHeartBeatClient() {
      }
  
      private static final String HOST = System.getProperty("host", "127.0.0.1");
      private static final int PORT = Integer.parseInt(System.getProperty("port", "1883"));
      private static final String CLIENT_ID = System.getProperty("clientId", "guestClient");
      private static final String USER_NAME = System.getProperty("userName", "guest");
      private static final String PASSWORD = System.getProperty("password", "guest");
  
      public static void main(String[] args) throws Exception {
          EventLoopGroup workerGroup = new NioEventLoopGroup();
  
          try {
              Bootstrap b = new Bootstrap();
              b.group(workerGroup);
              b.channel(NioSocketChannel.class);
              b.handler(new ChannelInitializer<SocketChannel>() {
                  @Override
                  protected void initChannel(SocketChannel ch) throws Exception {
                      ch.pipeline().addLast("encoder", MqttEncoder.INSTANCE);
                      ch.pipeline().addLast("decoder", new MqttDecoder());
                      ch.pipeline().addLast("heartBeatHandler", new IdleStateHandler(0, 20, 0, TimeUnit.SECONDS));
                      ch.pipeline().addLast("handler", new MqttHeartBeatClientHandler(CLIENT_ID, USER_NAME, PASSWORD));
                  }
              });
  
              ChannelFuture f = b.connect(HOST, PORT).sync();
              System.out.println("Client connected");
              f.channel().closeFuture().sync();
          } finally {
              workerGroup.shutdownGracefully();
          }
      }
  }