netty-socket客户端和服务端多次交互样例

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.81.Final</version>
        </dependency>

客户端:

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;

@Slf4j
@Component
public class NettyClientServer {

    public void test(String aaa) {
        NioEventLoopGroup nioEventLoopGroup = null;
        try {
            nioEventLoopGroup = new NioEventLoopGroup();
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(nioEventLoopGroup)
                    .channel(NioSocketChannel.class)
                    .handler(new MyClientInitializer(aaa));
            ChannelFuture channelFuture = bootstrap.connect("X.X.X.X", 8080).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            if (nioEventLoopGroup != null) {
                nioEventLoopGroup.shutdownGracefully();
            }
        }
    }
}

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;


public class MyClientInitializer extends ChannelInitializer<SocketChannel> {

    private final String aaa;
    public MyClientInitializer(String aaa) {
        this.aaa = aaa;
    }

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {

        //声明管道
        ChannelPipeline pipeline = ch.pipeline();
        //绑定自带的解码器，就是对二进制数据的解析工具，至于解码器构造方法的参数之后详细分析
        pipeline.addLast("lengthFieldBasedFrameDecoder", new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
        //编码器
        pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(4));
        //由于涉及到服务端和客户端的字符串数据，需要绑定字符串的编解码
        pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));
        //自定义处理器
        pipeline.addLast("myClientHandler", new NettyClientHandler(aaa));
    }
}

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;
import lombok.extern.slf4j.Slf4j;

@Slf4j
/**
 * Create by zjg on 2022/9/12
 */
public class NettyClientHandler extends ChannelInboundHandlerAdapter {

    private final String aaa;
    public NettyClientHandler(String aaa) {
        this.aaa = aaa;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("qqqq", CharsetUtil.UTF_8));
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("aaaaaaaa------------:" + aaa);
        System.out.println("接收到服务端响应:" + msg);
        if ("qqqq".equals(msg)) {
            ctx.writeAndFlush(Unpooled.copiedBuffer("2222", CharsetUtil.UTF_8));
        }
        if ("2222".equals(msg)) {
            ctx.writeAndFlush(Unpooled.copiedBuffer("3333", CharsetUtil.UTF_8));
        }
        if ("3333".equals(msg)) {
            ctx.writeAndFlush(Unpooled.copiedBuffer("4444", CharsetUtil.UTF_8));
        }
    }

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

服务端

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

import javax.annotation.PostConstruct;

@Slf4j
@Component
public class nettyClientServer {
    @PostConstruct
    public void createServerSocket() {
        NioEventLoopGroup bossGroup = null;
        NioEventLoopGroup workGroup = null;
        try {
            bossGroup = new NioEventLoopGroup();
            workGroup = new NioEventLoopGroup();
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup, workGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new MySocketServerInitializer());
            ChannelFuture channelFuture = bootstrap.bind(8080).sync();
            System.out.println("服务端启动完成!");
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            if (null != bossGroup) {
                bossGroup.shutdownGracefully();
            }
            if  (null != workGroup) {
                workGroup.shutdownGracefully();
            }
        }
    }
}

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;
import org.springframework.stereotype.Component;

@Component
public class MySocketServerInitializer extends ChannelInitializer<SocketChannel> {

        @Override
        protected void initChannel(SocketChannel ch) throws Exception {

            //声明管道
            ChannelPipeline pipeline = ch.pipeline();
            //绑定自带的解码器，就是对二进制数据的解析工具，至于解码器构造方法的参数之后详细分析
            pipeline.addLast("lengthFieldBasedFrameDecoder", new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
            /* 编码器 */
            pipeline.addLast("lengthFieldPrepender", new LengthFieldPrepender(4));
            //由于涉及到服务端和客户端的字符串数据，需要绑定字符串的编解码
            pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
            pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));
            //自定义处理器
            pipeline.addLast("mySocketServerHandler", new NettyServerHandler());

        }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class NettyServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        System.out.println(msg);
        ctx.writeAndFlush(msg);
    }

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