Netty实现长连接，客户端随时发送消息给服务端，可在任意代码位置发送消息给服务端

Netty实现长连接，客户端随时发送消息给服务端，可在任意代码位置发送消息给服务端

目录

pom依赖

netty服务端代码

netty客户端

PosttingObject封装netty客户端连接信息

测试客户端发送消息到服务器端

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1. 可以实现socket长连接，心跳机制每隔N秒客户端给服务器发送一条消息，代表客户端还存活。

2. 可以实现在随意代码位置按照用户id标识，发送消息给服务端。

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pom依赖

		
			io.netty
			netty-all
			4.1.36.Final
		

netty服务端代码

package com.kc.monitor.core.utils.netty;
 
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.SimpleChannelInboundHandler;
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;
 
public class NettyServer {
 
    
    private static int port = 8080;
 
    public static void main(String[] args) {
        
        // 用于接受客户端连接的请求 （并没有处理请求）
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        // 用于处理客户端连接的读写 *** 作
        NioEventLoopGroup workGroup = new NioEventLoopGroup();
        // 用于创建我们的ServerBootstrap
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workGroup).channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer() {
                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        // LinebasedframeDecoder解决粘包-解包问题，设置我们分割最大长度为1024
                        // 原理就是自动帮我们把带有n或rn的数据进行换行
                        //socketChannel.pipeline().addLast(new LinebasedframeDecoder(1024));
                        socketChannel.pipeline().addLast(new StringEncoder());// String编码器
                        socketChannel.pipeline().addLast(new StringDecoder());// String解码器
                        socketChannel.pipeline().addLast(new ServerHandler());// 管道类-接收发送消息
                    }
                });
        //  绑定我们的端口号码
        try {
            // 绑定端口号，同步等待成功
            ChannelFuture future = serverBootstrap.bind(port).sync();
            System.out.println("服务器启动成功：" + port);
            // 等待服务器监听端口
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
 
        } finally {
            // 优雅的关闭连接
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
 
}
 
 
class ServerHandler extends SimpleChannelInboundHandler {
 
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println("8080-msg:" + msg);
        // 响应内容:
        channelHandlerContext.writeAndFlush("8080n"); // String类型加上n会自动粘包和拆包了
    }
}

netty客户端

package com.kc.monitor.core.utils.netty;
 
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LinebasedframeDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
 
import java.net.InetSocketAddress;
import java.util.concurrent.ConcurrentHashMap;

public class NettyClient {

    
    public static ConcurrentHashMap concurrentHashMap = new ConcurrentHashMap();

    public ClientHandler clientHandler = new ClientHandler();

    public void initNetty(String userId, String host, int port){
        //创建nioEventLoopGroup
        NioEventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(group).channel(NioSocketChannel.class)
                .remoteAddress(new InetSocketAddress(host, port))
                .handler(new ChannelInitializer() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        System.out.println("正在连接中...");
                        ch.pipeline().addLast(new LinebasedframeDecoder(1024));
                        ch.pipeline().addLast(new StringDecoder());
                        ch.pipeline().addLast(new StringEncoder());
                        ch.pipeline().addLast(clientHandler);
                    }
                });

        try {
            // 发起连接
            ChannelFuture sync = bootstrap.connect().sync();
            System.out.println("用户："+userId + "->服务端连接成功...");

            

            // 异步等待关闭连接channel
            // sync.channel().closeFuture().sync();
            // System.out.println("连接已关闭..");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //group.shutdownGracefully();
            //System.out.println("优雅关闭连接");
        }

        PosttingObject posttingObject = new PosttingObject();
        posttingObject.setNioEventLoopGroup(group);
        posttingObject.setNettyClient(this);
        concurrentHashMap.put(userId, posttingObject);
    }

}
 
 
class ClientHandler extends SimpleChannelInboundHandler {

    public ChannelHandlerContext channelHandlerContext;

    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        channelHandlerContext = ctx;
        //channelHandlerContext.writeAndFlush("11111");
        //channelHandlerContext.channel().close();
    }
 
    
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println("接收消息：" + msg);
        //channelHandlerContext.channel().close();
    }
}

PosttingObject封装netty客户端连接信息

package com.kc.monitor.core.utils.netty;

import io.netty.channel.nio.NioEventLoopGroup;
import lombok.Data;


@Data
public class PosttingObject {

    private NettyClient nettyClient;

    private NioEventLoopGroup nioEventLoopGroup;

}

测试客户端发送消息到服务器端

package com.kc.monitor.core.utils.netty;



public class NettyClientSendMsg {

    private static final String host = "192.168.52.1";
    private static final int port = 8080;

    public static void main(String[] args) {
        // 初始化Netty连接
        String userId = "1";
        new NettyClient().initNetty(userId, host, port);



        // 根据用户id发送消息到客户端
        PosttingObject posttingObject = NettyClient.concurrentHashMap.get(userId);
        try{
            // 发送消息
            NettyClient nettyClient = posttingObject.getNettyClient();
            nettyClient.clientHandler.channelHandlerContext.writeAndFlush("01n");
            nettyClient.clientHandler.channelHandlerContext.writeAndFlush("02n");
            nettyClient.clientHandler.channelHandlerContext.writeAndFlush("03n");
        }finally {
            // 优雅关闭连接
            posttingObject.getNioEventLoopGroup().shutdownGracefully();
        }
    }


}