在Netty学习笔记(一) 实现DISCARD服务中，我们使用Netty和Python实现了简单的丢弃DISCARD服务，这篇，我们使用Netty实现服务端和客户端交互的需求。

前置工作

开发环境

• JDK8
• Netty版本:5.0.0.Alpha2
• 集成环境:IDEA
• 构建工具：Gradle

依赖

    compile group: 'io.netty', name: 'netty-all', version: '5.0.0.Alpha2'compile group: 'org.projectlombok', name: 'lombok', version: '1.18.0'

服务端

Netty服务器主要由两部分组成:

• 配置服务器功能，如线程、端口
• 实现服务器处理程序

服务端HandleAdapter

我们是首先实现服务端处理程序，实现Handle要求继承HandleAdapter,这里我们继承SimpleChannelInboundHandler<T>,下面是具体实现的代码信息,其每个函数的作用，我们只需要重写我们所需要的方法即可。

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;/*** Netty 服务Handle** @author tao*/
@ChannelHandler.Sharable
public class EchoServiceHandle extends SimpleChannelInboundHandler<String> {/*** 接收到新的消息* @param ctx* @param msg* @throws Exception*/@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {// 打印接收到的消息System.out.println("Netty服务端接收到消息 " + msg);// 回复消息ctx.channel().writeAndFlush("Send ----> 客户端" + ctx.channel().id() + "你好，我已经接收到你发送的消息");}/*** 有新的连接加入* @param ctx* @throws Exception*/@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {System.out.println("接入新的Channel,id = " + ctx.channel().id());}/*** 服务端发生异常信息的时候* @param ctx* @param cause*/@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {// 服务端发生异常System.out.println("Netty 服务端发生异常 ,异常信息：" + cause);ctx.close();}@Overrideprotected void messageReceived(ChannelHandlerContext ctx, String msg) {}
}

服务端启动

在服务端的EchoServiceHandle完成之后，我们需要配置服务器的参数信息，比如端口等

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import lombok.Data;/*** @author tao*/
@Data
public class EchoService {private int port;public void start() throws Exception {EventLoopGroup boosGroup = new NioEventLoopGroup();EventLoopGroup workGroup = new NioEventLoopGroup();try {ServerBootstrap bootstrap = new ServerBootstrap();bootstrap.group(boosGroup, workGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 128).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();//字符串解码器pipeline.addLast(new StringDecoder());//字符串编码器pipeline.addLast(new StringEncoder());//服务端处理器pipeline.addLast(new EchoServiceHandle());}});ChannelFuture sync = bootstrap.bind(port).sync();System.out.println("Netty Service start with " + port + "...");sync.channel().closeFuture().sync();} finally {workGroup.shutdownGracefully();boosGroup.shutdownGracefully();}}public static void main(String[] args) throws Exception {EchoService service = new EchoService();service.setPort(8080);service.start();}
}

启动后，我们可以看到启动信息如下:

Netty Service start with 8080...

客户端

客户端和服务端类似,可以相互参考学习.

客户端HandleAdapter

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;@ChannelHandler.Sharable
public class EchoClientHandle extends SimpleChannelInboundHandler<String> {/*** 连接创建成功的时候* @param ctx* @throws Exception*/@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {System.out.println("channelActive");//连接成功后向服务端发送问候消息ctx.channel().writeAndFlush(Unpooled.copiedBuffer("你好，这里是Netty客户端", CharsetUtil.UTF_8));}/*** 发生异常* @param ctx* @param cause*/@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {System.out.println("exceptionCaught");cause.printStackTrace();ctx.close();}/*** 接收到服务端发过来的数据* @param ctx* @param msg*/@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) {//打印接收到的数据信息System.out.println("channelRead = " + msg);}@Overrideprotected void messageReceived(ChannelHandlerContext ctx, String msg) {}
}

客户端启动

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import lombok.Data;
import lombok.experimental.Accessors;
import lombok.extern.slf4j.Slf4j;import java.net.InetSocketAddress;/** @author tao */
@Data
@Accessors(chain = true)
@Slf4j
public class EchoClient {private int port;private String host;public void start() throws Exception {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// 字符串解码器pipeline.addLast(new StringDecoder());// 字符串编码器pipeline.addLast(new StringEncoder());pipeline.addLast(new EchoClientHandle());}});ChannelFuture sync = bootstrap.connect(new InetSocketAddress(host, port)).sync();sync.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {group.shutdownGracefully().sync();}}public static void main(String[] args) throws Exception {EchoClient client = new EchoClient();client.setHost("127.0.0.1").setPort(8080);client.start();}
}

效果

服务端效果

   Netty Service start with 8080...接入新的Channel,id = c0d4f037Netty服务端接收到消息 你好，这里是Netty客户端

客户端效果

channelActive
channelRead = Send ----> 客户端c0d4f037你好，我已经接收到你发送的消息