使用Netty解决TCP粘包和拆包问题过程详解

public class PrintServer {

 public void bind(int port) throws Exception {
 // 配置服务端的NIO线程组
 EventLoopGroup bossGroup = new NioEventLoopGroup();
 EventLoopGroup workerGroup = new NioEventLoopGroup();
 try {
  ServerBootstrap b = new ServerBootstrap();
  b.group(bossGroup, workerGroup)
   .channel(NioServerSocketChannel.class)
   .option(ChannelOption.SO_BACKLOG, 1024)
   .childHandler(new ChildChannelHandler());
  // 绑定端口，同步等待成功
  ChannelFuture f = b.bind(port).sync();

  // 等待服务端监听端口关闭
  f.channel().closeFuture().sync();
 } finally {
  // 优雅退出，释放线程池资源
  bossGroup.shutdownGracefully();
  workerGroup.shutdownGracefully();
 }
 }

 private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
 @Override
 protected void initChannel(SocketChannel arg0) throws Exception {
  arg0.pipeline().addLast(new LineBasedFrameDecoder(1024)); //1
  arg0.pipeline().addLast(new StringDecoder());    //2
  arg0.pipeline().addLast(new PrintServerHandler());
 }
 }


 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;          
 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);            
 } 

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


 @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();     
 try {
  Bootstrap b = new Bootstrap();        
   b.group(group)            
   .channel(NioSocketChannel.class)      
   .option(ChannelOption.TCP_NODELAY, true)    
   .handler(new ChannelInitializer<SocketChannel>() {  
   @Override
   public void initChannel(SocketChannel ch)    
    throws Exception {
     ch.pipeline().addLast(
     new LineBasedFrameDecoder(1024));   //3
    ch.pipeline().addLast(new StringDecoder());  //4
    ch.pipeline().addLast(new PrintClientHandler());
   }
   });

  ChannelFuture f = b.connect(host, port).sync();    
  f.channel().closeFuture().sync();       
 } 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);        
 firstMessage.writeBytes(req);

 }

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

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

   public void initChannel(SocketChannel ch)    
    ByteBuf delimiter = Unpooled.copiedBuffer("_".getBytes()); //1
    ch.pipeline().addLast(
     new DelimiterBasedFrameDecoder(1024,
      delimiter));          //2
    ch.pipeline().addLast(new StringDecoder());     //3
    ch.pipeline().addLast(new PrintHandler());
   }

 public void initChannel(SocketChannel ch)
    throws Exception {
    ch.pipeline().addLast(new FixedLengthFrameDecoder(20));
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new PrintHandler());
   }
   });