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   /*
    * Copyright 2012 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.uptime;
  
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.timeout.IdleState;
  import io.netty.handler.timeout.IdleStateEvent;
  
  import java.util.concurrent.TimeUnit;
  
  /**
   * Keep reconnecting to the server while printing out the current uptime and
   * connection attempt getStatus.
   */
  @Sharable
  public class UptimeClientHandler extends SimpleChannelInboundHandler<Object> {
  
      long startTime = -1;
  
      @Override
      public void channelActive(ChannelHandlerContext ctx) {
          if (startTime < 0) {
              startTime = System.currentTimeMillis();
          }
          println("Connected to: " + ctx.channel().remoteAddress());
      }
  
      @Override
      public void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
          // Discard received data
      }
  
      @Override
      public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
          if (!(evt instanceof IdleStateEvent)) {
              return;
          }
  
          IdleStateEvent e = (IdleStateEvent) evt;
          if (e.state() == IdleState.READER_IDLE) {
              // The connection was OK but there was no traffic for last period.
              println("Disconnecting due to no inbound traffic");
              ctx.close();
          }
      }
  
      @Override
      public void channelInactive(final ChannelHandlerContext ctx) {
          println("Disconnected from: " + ctx.channel().remoteAddress());
      }
  
      @Override
      public void channelUnregistered(final ChannelHandlerContext ctx) throws Exception {
          println("Sleeping for: " + UptimeClient.RECONNECT_DELAY + 's');
  
          ctx.channel().eventLoop().schedule(new Runnable() {
              @Override
              public void run() {
                  println("Reconnecting to: " + UptimeClient.HOST + ':' + UptimeClient.PORT);
                  UptimeClient.connect();
              }
          }, UptimeClient.RECONNECT_DELAY, TimeUnit.SECONDS);
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
          cause.printStackTrace();
          ctx.close();
      }
  
      void println(String msg) {
          if (startTime < 0) {
              System.err.format("[SERVER IS DOWN] %s%n", msg);
          } else {
              System.err.format("[UPTIME: %5ds] %s%n", (System.currentTimeMillis() - startTime) / 1000, msg);
          }
      }
  }