什么是Echo服务

就是一个应答服务（回显服务器），客户端发送什么数据，服务端就响应的对应的数据。
是一个非常有的用于调试和检测的服务

 <dependencies>
        <!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.32.Final</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

echo服务端

server:
  port: 8080

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import lombok.extern.log4j.Log4j2;

/**
 * echo服务端
 *
 * @author zhou
 */
@Log4j2
public class EchoServer {

    private int port;

    public EchoServer(int port) {
        this.port = port;
    }

    public void run() throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap()
                    .group(bossGroup, workGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new EchoServerHandler());
                        }
                    });
            log.info("echo服务端启动 ====== 端口号为{}", port);
            ChannelFuture channelFuture = serverBootstrap.bind(port).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }


}

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;

/**
 * @author zhou
 */
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf data = (ByteBuf) msg;
        String s = data.toString(CharsetUtil.UTF_8);
        System.out.println("EchoServer 收到数据 :" + s);
        // 回显数据
        ctx.writeAndFlush(data);
    }



    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        System.out.println("EchoServerHandler channelReadComplete");
    }

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

import lombok.extern.log4j.Log4j2;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * @author zhou
 */
@Component
@Order(1)
@Log4j2
public class EchoServerRunner implements CommandLineRunner {

    @Override
    public void run(String... args) throws InterruptedException {
        log.info("项目启动时进行初始化EchoServerRunner操作");
        new EchoServer(8081).run();
    }

}

echo客户端

server:
  port: 8082

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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 java.net.InetSocketAddress;

/**
 * 客户端
 *
 * @author zhou
 */
public class EchoClient {

    private String host;

    private int port;

    public EchoClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void start() throws InterruptedException {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .remoteAddress(new InetSocketAddress(host, port))
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new EchoClientHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.connect().sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }


}

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;

/**
 * @author zhou
 */
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf msg) throws Exception {
        System.out.println("客户端收到服务端信息："+msg.toString(CharsetUtil.UTF_8));
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("EchoClientHandler channelActive");
        String msg = "你好啊";
        ctx.writeAndFlush(Unpooled.copiedBuffer(msg,CharsetUtil.UTF_8));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        System.out.println("EchoClientHandler channelReadComplete");
    }

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

import lombok.extern.log4j.Log4j2;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * @author zhou
 */
@Component
@Order(1)
@Log4j2
public class EchoClientRunner implements CommandLineRunner {

    @Override
    public void run(String... args) throws InterruptedException {
        log.info("项目启动时进行初始化EchoClientRunner操作");
        new EchoClient("127.0.0.1",8081).start();
    }

}

先启动服务端后启动客户端