[网络协议]Netty从使用到源码6_实现简单双向通信

1. 实现功能

双向通信，客户端向服务器发送什么，服务器就向客户端发送什么

2. 服务器代码

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

import java.nio.charset.Charset;

public class DoubleServer {

    public static void main(String[] args) {
        new ServerBootstrap()
                .group(new NioEventLoopGroup())
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) {
                        /**
                         * 客户端有数据发来时执行此handler.
                         * */
                        ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) {
                                //直接拿到客户端发来的数据。
                                ByteBuf buffer = (ByteBuf) msg;
                                System.out.println(buffer.toString(Charset.defaultCharset()));
                                /**
                                 * 建议使用 ctx.alloc() 创建 ByteBuf
                                 * 将客户端发来的消息转换为ButeBuf向客户端写回去
                                 */
                                ByteBuf response = ctx.alloc().buffer();
                                response.writeBytes(buffer);

                                /**
                                 *  向服务器写。也可以调用channel()先获取channel然后写
                                 *  Channel channel = ctx.channel();
                                 *  channel.writeAndFlush(response);
                                 */
                                ctx.writeAndFlush(response);
                            }
                        });
                    }
                }).bind(8080);
    }
}

3. 客户端代码

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringEncoder;

import java.nio.charset.Charset;
import java.util.Scanner;

public class DoubleClient {
    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup group = new NioEventLoopGroup();
        Channel channel = new Bootstrap()
                .group(group)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new StringEncoder());
                        /*
                         * 收到服务器的数据时执行此方法
                         * */
                        ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                            @Override
                            public void channelRead(ChannelHandlerContext ctx, Object msg) {
                                //由于服务器传输的是一个ByteBuf，这里直接强转
                                ByteBuf buffer = (ByteBuf) msg;
                                System.out.println(buffer.toString(Charset.defaultCharset()));
                            }
                        });
                    }
                }).connect("127.0.0.1", 8080).sync().channel();

        /*
         * 一旦channle调用close()方法，执行这里的逻辑
         * 异步回调关闭连接后，关闭线程池组。
         * */
        channel.closeFuture().addListener(future -> {
            group.shutdownGracefully();
        });

        /*
         * 控制台输入，然后调用writeAndFlush向服务器传输数据
         * */
        new Thread(() -> {
            Scanner scanner = new Scanner(System.in);
            while (true) {
                String line = scanner.nextLine();
                if ("q".equals(line)) {
                    channel.close();
                    break;
                }
                //向服务器写
                channel.writeAndFlush(line);
            }
        }).start();
    }
}

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