一、环境

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.17.Final</version>
</dependency>

二、代码

1、NettyServer代码

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

public class NettyServer {

    private static final String ip = "127.0.0.1";
    private static final int port = 6666;
    private static final EventLoopGroup bossGroup = new NioEventLoopGroup();
    private static final EventLoopGroup workerGroup = new NioEventLoopGroup();

    public static void start() throws Exception {
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<Channel>() {
                    protected void initChannel(Channel ch) throws Exception {
                        ChannelPipeline pipeline = ch.pipeline();
                        pipeline.addLast(new SocketHandler());
                    }
                });

        ChannelFuture channelFuture = serverBootstrap.bind(ip, port).sync();
        channelFuture.channel().closeFuture().sync();
        System.out.println("server start");
    }

    protected static void shutdown() {
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }

    public static void main(String[] args) throws Exception {
        System.out.println("启动server");
        NettyServer.start();
    }
}

2、SocketHandler代码

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class SocketHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("channel active>>>>>>>");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        ByteBuf message = (ByteBuf) msg;
        byte[] response = new byte[message.readableBytes()];
        message.readBytes(response);
        System.out.println("receive client info: " + new String(response));

        String sendContent = "hello client ,im server, this is u say:" + new String(response);
        ByteBuf seneMsg = Unpooled.buffer(sendContent.length());
        seneMsg.writeBytes(sendContent.getBytes());

        ctx.writeAndFlush(seneMsg);
        System.out.println("send info to client:" + sendContent);
    }

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

3、客户端Socket代码

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.atomic.AtomicInteger;

public class SocketClient {

    public static void send(String message){
        Socket socket = null;
        try {
            socket = new Socket("127.0.0.1", 6666);
            PrintWriter out = new PrintWriter(socket.getOutputStream());
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            out.println(message);
            out.flush();

            System.out.println("server:" + in.readLine());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if(socket != null){
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws UnknownHostException {
        SocketClient.send("aaaa");
    }

}