Netty 是一款异步的、基于事件驱动的网络应用程序框架，用以快速开发高性能、高可靠性的网络 IO 程序。

引入依赖

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.77.Final</version>
</dependency>

服务端

服务端监听 8081 端口

package com.example.demo.nettydemo;

import io.netty.bootstrap.ServerBootstrap;
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 io.netty.handler.codec.string.StringDecoder;

import java.util.Date;

public class HelloWorldServer {
    public static void main(String[] args) {
        // 创建服务端启动引导器
        ServerBootstrap bootstrap = new ServerBootstrap();
        // 配置线程模型
        bootstrap.group(new NioEventLoopGroup());
        // 指定服务端的 IO 模型
        bootstrap.channel(NioServerSocketChannel.class);
        // 定义处理器 Handler
        bootstrap.childHandler(new ChannelInitializer<NioSocketChannel>() {
            @Override
            protected void initChannel(NioSocketChannel channel) throws Exception {
                // 解码
                channel.pipeline().addLast(new StringDecoder());

                channel.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                    @Override
                    public void channelActive(ChannelHandlerContext ctx) throws Exception {
                        System.out.println(ctx.channel() + ",hello world");
                    }

                    @Override
                    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                        System.out.println(new Date() + "：" + msg);
                    }
                });
            }
        });

        // 绑定 8081 端口
        bootstrap.bind(8081);
    }
}

客户端

客户端每隔5秒给服务端发送一条信息

package com.example.demo.nettydemo;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
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.StringEncoder;

import java.util.concurrent.TimeUnit;

public class HelloWorldClient {
    public static void main(String[] args) throws InterruptedException {
        // 客户端引导器
        Bootstrap bootstrap = new Bootstrap();
        // 配置线程组
        bootstrap.group(new NioEventLoopGroup());
        // 指定 IO 类型为 NIO
        bootstrap.channel(NioSocketChannel.class);
        // 配置 IO 处理器
        bootstrap.handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
                ch.pipeline().addLast(new StringEncoder());
            }
        });
        
        // 建立连接
        Channel channel = bootstrap.connect("127.0.0.1",8081).channel();
        // 发送消息
        while (true) {
            channel.writeAndFlush("hello world..");
            TimeUnit.SECONDS.sleep(5);
        }
    }
}

参考文章

1. Netty 入门 — 亘古不变的Hello World