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Netty（一）之helloworld

news 2026/7/28 18:35:21

HelloWorld

客户端通向服务器端发送消息，服务器端读取数据（你好）并且返回（new Date()），客户端读取数据

pom

<dependency> <groupId>io.netty</groupId> <artifactId>netty-all</artifactId> <version>5.0.0.Alpha1</version> </dependency>

TimeServerHandler

服务器端读取数据并且回应请求，继承ChannelHandlerAdapter并且实现channelRead和exceptionCaught方法

package myhelloworld; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerAdapter; import io.netty.channel.ChannelHandlerContext; import java.util.Date; /** * @author CBeann * @create 2019-08-27 18:31 */ public class TimeServerHandler extends ChannelHandlerAdapter { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { //服务器读客户端发送来的数据 ByteBuf buf = (ByteBuf) msg; byte[] req = new byte[buf.readableBytes()]; buf.readBytes(req); String body = new String(req, "UTF-8"); System.out.println("The TimeServer receive :" + body); //服务器向客户端回应请求 ByteBuf response = Unpooled.copiedBuffer(new Date().toString().getBytes()); ctx.writeAndFlush(response); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ctx.close(); } // }

TimeServer

package myhelloworld; import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel; /** * @author CBeann * @create 2019-08-27 18:22 */ public class TimeServer { public static void main(String[] args) throws Exception { int port = 8080; //配置服务器端的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 ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel socketChannel) throws Exception { //TimeClientHandler是自己定义的方法 socketChannel.pipeline().addLast(new TimeServerHandler()); } }); //绑定端口 ChannelFuture f = b.bind(port).sync(); //等待服务端监听端口关闭 f.channel().closeFuture().sync(); } catch (Exception e) { } finally { //优雅关闭，释放线程池资源 bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); } } }

启动NettyServer的模版代码

private void bing(int port) { EventLoopGroup parentGroup = new NioEventLoopGroup(); EventLoopGroup childGroup = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); b.group(parentGroup, childGroup) .channel(NioServerSocketChannel.class) //非阻塞模式 .option(ChannelOption.SO_BACKLOG, 128) .childHandler(new MyChannelInitializer()); ChannelFuture f = b.bind(port).sync(); System.out.println("itstack-demo-netty server start done. {关注公众号：bugstack虫洞栈，获取源码}"); f.channel().closeFuture().sync(); } catch (InterruptedException e) { e.printStackTrace(); } finally { childGroup.shutdownGracefully(); parentGroup.shutdownGracefully(); } }

TimeClientHandler

客户端读取服务器响应数据，继承ChannelHandlerAdapter并且实现channelRead和exceptionCaught方法

package myhelloworld; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerAdapter; import io.netty.channel.ChannelHandlerContext; import io.netty.util.ReferenceCountUtil; /** * @author CBeann * @create 2019-08-27 18:47 */ public class TimeClientHandler extends ChannelHandlerAdapter { //客户端读取服务器发送的数据 @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try { ByteBuf buf = (ByteBuf) msg; byte[] req = new byte[buf.readableBytes()]; buf.readBytes(req); String body = new String(req, "UTF-8"); System.out.println("Now is:" + body); } catch (Exception e) { } finally { //标配 ReferenceCountUtil.release(msg); } } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ctx.close(); } }

TimeClient

package myhelloworld; import io.netty.bootstrap.Bootstrap; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioSocketChannel; /** * @author CBeann * @create 2019-08-27 18:43 */ public class TimeClient { public static void main(String[] args) throws Exception { int port = 8080; String host = "127.0.0.1"; //配置客户端NIO线程组 EventLoopGroup group = new NioEventLoopGroup(); try { Bootstrap b = new Bootstrap(); b.group(group) .channel(NioSocketChannel.class) .handler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel socketChannel) throws Exception { //TimeClientHandler是自己定义的方法 socketChannel.pipeline().addLast(new TimeClientHandler()); } }); //发起异步连接操作 ChannelFuture f = b.connect(host, port).sync(); //发送数据 f.channel().writeAndFlush(Unpooled.copiedBuffer("您好".getBytes())); //Thread.sleep(1000);//防止TCP粘包 //f.channel().writeAndFlush(Unpooled.copiedBuffer("您好".getBytes())); //Thread.sleep(1000); //f.channel().writeAndFlush(Unpooled.copiedBuffer("您好".getBytes())); //Thread.sleep(1000); //等待客户端链路关闭 f.channel().closeFuture().sync(); } catch (Exception e) { } finally { //优雅关闭 group.shutdownGracefully(); } } }