使用Netty搭建服务端和客户端过程详解

public class PrintServer {

  public void bind(int port) throws Exception {
    EventLoopGroup bossGroup = new NioEventLoopGroup();           //1
    EventLoopGroup workerGroup = new NioEventLoopGroup();          //2
    try {
      ServerBootstrap b = new ServerBootstrap();             //3
      b.group(bossGroup, workerGroup)                   //4                     
          .channel(NioServerSocketChannel.class)           //5
          .option(ChannelOption.SO_BACKLOG, 1024)           //6
          .childHandler(new ChannelInitializer<SocketChannel>() {   //7
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
              ch.pipeline().addLast(new PrintServerHandler());
            }
          });

      ChannelFuture f = b.bind(port).sync();       //8
      
      f.channel().closeFuture().sync();          //9
    } finally {
      // 优雅退出，释放线程池资源
      bossGroup.shutdownGracefully();
      workerGroup.shutdownGracefully();
    }
  }


  /**
   * @param args
   * @throws Exception
   */
  public static void main(String[] args) throws Exception {
    int port = 8080;
    new TimeServer().bind(port);
  }
}

public class PrintServerHandler extends ChannelHandlerAdapter {

  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg)
    throws Exception {
  ByteBuf buf = (ByteBuf) msg;                    //1
  byte[] req = new byte[buf.readableBytes()]; 
  buf.readBytes(req); //将缓存区的字节数组复制到新建的req数组中
  String body = new String(req, "UTF-8");
  System.out.println(body);
  String response= "打印成功";
  ByteBuf resp = Unpooled.copiedBuffer(response.getBytes());           
  ctx.write(resp);                          //2
  }  

  @Override
  public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
  ctx.flush();                            //3
  }


  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
  ctx.close();
  }
}

public class PrintClient {

  public void connect(int port, String host) throws Exception {
  EventLoopGroup group = new NioEventLoopGroup();         //1
  try {
    Bootstrap b = new Bootstrap();               //2
     b.group(group)                       //3
      .channel(NioSocketChannel.class)            //4
      .option(ChannelOption.TCP_NODELAY, true)        //5
      .handler(new ChannelInitializer<SocketChannel>() {   //6
      @Override
      public void initChannel(SocketChannel ch)        
        throws Exception {
        ch.pipeline().addLast(new PrintClientHandler());
      }
      });

    ChannelFuture f = b.connect(host, port).sync();       //7
    f.channel().closeFuture().sync();              //8
  } finally {
    // 优雅退出，释放NIO线程组
    group.shutdownGracefully();
  }
  }

  /**
   * @param args
   * @throws Exception
   */
  public static void main(String[] args) throws Exception {
  int port = 8080;
  new TimeClient().connect(port, "127.0.0.1");
  }
}

public class PrintClientHandler extends ChannelHandlerAdapter {

  private static final Logger logger = Logger
    .getLogger(TimeClientHandler.class.getName());

  private final ByteBuf firstMessage;

  /**
   * Creates a client-side handler.
   */
  public TimeClientHandler() {
  byte[] req = "你好服务端".getBytes();
  firstMessage = Unpooled.buffer(req.length);                 //1
  firstMessage.writeBytes(req);

  }

  @Override
  public void channelActive(ChannelHandlerContext ctx) {
  ctx.writeAndFlush(firstMessage);                      //2       
  }

  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg)       //3
    throws Exception {
  ByteBuf buf = (ByteBuf) msg;  
  byte[] req = new byte[buf.readableBytes()];
  buf.readBytes(req);
  String body = new String(req, "UTF-8");
  System.out.println("服务端回应消息 : " + body);
  }

  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {  //4
  // 释放资源
  System.out.println("Unexpected exception from downstream : "
    + cause.getMessage());
  ctx.close();
  }
}