Netty 群聊实现

    用netty 实现一个群聊，服务端接收客户端消息，并且转发给其他用户。无论是群聊还是单聊，都是由服务器端进行转发。

1. ChatServer

package netty.chat;

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;

public class ChatServer {

    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerExecutors = new NioEventLoopGroup();

        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workerExecutors)
                .channel(NioServerSocketChannel.class) // 设置服务器的通道
                .option(ChannelOption.SO_BACKLOG, 128) // 设置线程队列得到连接个数
                .childOption(ChannelOption.SO_KEEPALIVE, true) // 设置保持活动连接状态
                .childHandler(new ChannelInitializer<SocketChannel>() { // 设置通道测试对象(匿名对象)
                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        ChannelPipeline pipeline = socketChannel.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());
                        // 给pipeline添加一个handler
                        socketChannel.pipeline().addLast(new ChatServerHandler());
                    }
                });

        ChannelFuture sync = serverBootstrap.bind(8989).sync();
        sync.addListener(future -> {
            if (future.isSuccess()) {
                System.out.println("服务器绑定8989端口成功");
            }
        });
    }
}

2. ChatServerHandler

package netty.chat;

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 java.text.SimpleDateFormat;
import java.util.Date;

public class ChatServerHandler 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
    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    // 用于格式化日期
    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    /**
     * handlerAdded 表示连接建立，一旦连接，第一个被执行。将当前channel 加入到  channelGroup
     */
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        // 将该客户加入聊天的信息推送给其它在线的客户端, 该方法会将 channelGroup 中所有的channel 遍历，并发送消息，
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 加入聊天" + sdf.format(new Date()) + " 
");
        channelGroup.add(channel);
    }

    /**
     * channel 关闭事件
     */
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 离开了
");
        System.out.println("channelGroup size" + channelGroup.size());
    }

    /**
     * channel 活跃
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 上线了~");
    }

    /**
     * channel 不活跃
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 离线了~");
    }

    /**
     * 读取消息
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        Channel channel = ctx.channel();
        //这时我们遍历channelGroup, 根据不同的情况，回送不同的消息
        channelGroup.forEach(ch -> {
            if (channel != ch) { //不是当前的channel,转发消息
                ch.writeAndFlush("[客户]" + channel.remoteAddress() + " 发送了消息" + msg + "
");
            } else { // 回显自己发送的消息给自己
                ch.writeAndFlush("[自己]发送了消息" + msg + "
");
            }
        });
    }

    /**
     * 异常发生
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        //关闭通道
        ctx.close();
    }
}

3. ChatClient

package netty.chat;

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.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.util.Scanner;

public class ChatClient {

    private final String host;
    private final int port;

    public ChatClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void run() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            //得到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //加入相关handler
                            pipeline.addLast("decoder", new StringDecoder());
                            pipeline.addLast("encoder", new StringEncoder());
                            //加入自定义的handler
                            pipeline.addLast(new ChatClientHandler());
                        }
                    });

            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();
            // 得到channel
            Channel channel = channelFuture.channel();
            System.out.println("-------" + channel.localAddress() + "--------");
            // 客户端需要输入信息，创建一个扫描器
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNextLine()) {
                String msg = scanner.nextLine();
                //通过channel 发送到服务器端
                channel.writeAndFlush(msg + "
");
            }
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new ChatClient("127.0.0.1", 8989).run();
    }
}

4.  ChatClientHandler

package netty.chat;


import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class ChatClientHandler extends SimpleChannelInboundHandler<String> {

    /**
     * 读取消息事件
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(msg.trim());
    }
}

上面代码已经完成了群聊，在群聊的基础上加入心跳检测机制：当服务器超过3秒没有读时，就提示读空闲；当服务器超过5秒没有写操作时，就提示写空闲；实现当服务器超过7秒没有读或者写操作时，就提示读写空闲

1. 修改服务器端代码加入心跳检测

package netty.chat;

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;
import io.netty.handler.timeout.IdleStateHandler;
import netty.heat.MyServerHandler;

import java.util.concurrent.TimeUnit;

public class ChatServer {

    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerExecutors = new NioEventLoopGroup();

        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(bossGroup, workerExecutors)
                .channel(NioServerSocketChannel.class) // 设置服务器的通道
                .option(ChannelOption.SO_BACKLOG, 128) // 设置线程队列得到连接个数
                .childOption(ChannelOption.SO_KEEPALIVE, true) // 设置保持活动连接状态
                .childHandler(new ChannelInitializer<SocketChannel>() { // 设置通道测试对象(匿名对象)
                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        ChannelPipeline pipeline = socketChannel.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());
                        // 给pipeline添加一个handler
                        socketChannel.pipeline().addLast(new ChatServerHandler());

                        // 加入一个netty 提供的 IdleStateHandler
                        /*
                            说明
                            1. IdleStateHandler 是netty 提供的处理空闲状态的处理器
                            2. long readerIdleTime : 表示多长时间没有读, 就会发送一个心跳检测包检测是否连接
                            3. long writerIdleTime : 表示多长时间没有写, 就会发送一个心跳检测包检测是否连接
                            4. long allIdleTime : 表示多长时间没有读写, 就会发送一个心跳检测包检测是否连接
                            5. 文档说明
                            triggers an {@link IdleStateEvent} when a {@link Channel} has not performed read, write, or both operation for a while.
                            6. 当 IdleStateEvent 触发后 , 就会传递给管道 的下一个handler去处理
                            通过调用(触发)下一个handler 的 userEventTiggered , 在该方法中去处理 IdleStateEvent(读空闲，写空闲，读写空闲)
                         */
                        pipeline.addLast(new IdleStateHandler(7000, 7000, 10, TimeUnit.SECONDS));
                        //加入一个对空闲检测进一步处理的handler(自定义)
                        pipeline.addLast(new MyServerHandler());
                    }
                });

        ChannelFuture sync = serverBootstrap.bind(8989).sync();
        sync.addListener(future -> {
            if (future.isSuccess()) {
                System.out.println("服务器绑定8989端口成功");
            }
        });
    }
}

2. MyServerHandler 心跳检测

package netty.heat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleStateEvent;

public class MyServerHandler extends ChannelInboundHandlerAdapter {

    public MyServerHandler() {
        System.out.println("netty.heat.MyServerHandler.MyServerHandler");
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            //将  evt 向下转型 IdleStateEvent
            IdleStateEvent event = (IdleStateEvent) evt;
            String eventType = null;
            switch (event.state()) {
                case READER_IDLE:
                    eventType = "读空闲";
                    break;
                case WRITER_IDLE:
                    eventType = "写空闲";
                    break;
                case ALL_IDLE:
                    eventType = "读写空闲";
                    break;
            }

            System.out.println(ctx.channel().remoteAddress() + "--超时时间--" + eventType);
            System.out.println("服务器做相应处理..");
            //如果发生空闲，我们关闭通道
            // ctx.channel().close();
        }
    }
}