SpringBoot中使用Netty实现TCP通讯，服务器主动向客户端发送数据

简述：

Springboot项目的web服务后台，web服务运行在9100端口。

后台使用netty实现了TCP服务，运行在8000端口。

启动截图如下：

pom依赖

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.25.Final</version>
        </dependency>

netty服务代码

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

/**
 * netty服务器，主要用于与客户端通讯
 */
public class NettyServer {
    private final int port; //监听端口


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

    //编写run方法，处理客户端的请求
    public void run() throws Exception {

        //创建两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(); //8个NioEventLoop

        try {
            ServerBootstrap b = new ServerBootstrap();

            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            //获取到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //向pipeline加入解码器
                            pipeline.addLast("decoder", new StringDecoder());
                            //向pipeline加入编码器
                            pipeline.addLast("encoder", new StringEncoder());
                            //加入自己的业务处理handler
                            pipeline.addLast(new NettyServerHandler());

                        }
                    });
            System.out.println("netty服务器启动成功（port:" + port + "）......");
            ChannelFuture channelFuture = b.bind(port).sync();
            //监听关闭
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

}

netty业务处理handler

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class NettyServerHandler extends SimpleChannelInboundHandler<String> {

    //定义一个channle 组，管理所有的channel
    //GlobalEventExecutor.INSTANCE) 是全局的事件执行器，是一个单例
    public static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    /**
     * 有客户端与服务器发生连接时执行此方法
     * 1.打印提示信息
     * 2.将客户端保存到 channelGroup 中
     */
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        System.err.println("有新的客户端与服务器发生连接。客户端地址：" + channel.remoteAddress());
        channelGroup.add(channel);
    }

    /**
     * 当有客户端与服务器断开连接时执行此方法，此时会自动将此客户端从 channelGroup 中移除
     * 1.打印提示信息
     */
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        System.err.println("有客户端与服务器断开连接。客户端地址：" + channel.remoteAddress());
    }

    /**
     * 表示channel 处于活动状态
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 处于活动状态");
    }

    /**
     * 表示channel 处于不活动状态
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 处于不活动状态");
    }

    /**
     * 读取到客户端发来的数据数据
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) {
        //获取到当前channel
        Channel channel = ctx.channel();
        System.err.println("有客户端发来的数据。地址：" + channel.remoteAddress() + " 内容：" + msg);
    }

    /**
     * 处理异常
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        log.error("发生异常。异常信息：{}", cause.getMessage());
        //关闭通道
        ctx.close();
    }
}