<dependencies>
    <dependency>
      <groupId>io.netty</groupId>
      <artifactId>netty-all</artifactId>
      <version>4.1.69.Final</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.24</version>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.51</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.32</version>
    </dependency>
    <dependency>
      <groupId>cn.hutool</groupId>
      <artifactId>hutool-all</artifactId>
      <version>5.8.0.M2</version>
    </dependency>
</dependencies>

package com.chat.model;
import lombok.Data;
import java.io.Serializable;
@Data
public class MessageHead implements Serializable {
    /**
     * 指令
     */
    private Integer commond;
    /**
     * 版本號(hào)
     */
    private Integer version;
    /**
     * clientType(WEB,IOS,Android)
     */
    private Integer clientType;
    /**
     * 數(shù)據(jù)解析類型 和具體業(yè)務(wù)無(wú)關(guān)，后續(xù)根據(jù)解析類型解析data數(shù)據(jù) 0x0:Json,0x1:ProtoBuf,0x2:Xml,默認(rèn):0x0
     */
    private Integer messageType = 0x0;
    /**
     * imei號(hào)長(zhǎng)度
     */
    private Integer imeiLen;
    /**
     * appId
     */
    private Integer appId;
    /**
     * bodyLen,數(shù)據(jù)長(zhǎng)度
     */
    private Integer bodyLen;
}

package com.chat.model;
import lombok.Data;
import java.io.Serializable;
@Data
public class MessageBody implements Serializable {
    /**
     * imei號(hào)
     */
    private String imei;
    /**
     * 數(shù)據(jù)
     */
    private Object data;
}

package com.chat.model;
import lombok.Data;
import java.io.Serializable;
// Message就是我們Netty服務(wù)接收到的完整的(請(qǐng)求頭+請(qǐng)求體)數(shù)據(jù)包
@Data
public class Message implements Serializable {
    private MessageHead messageHead;
    private MessageBody messageBody;
}

package com.chat.codec;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.chat.model.Message;
import com.chat.model.MessageBody;
import com.chat.model.MessageHead;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import java.util.List;
/**
 * 自定義編碼器
 */
public class MessageDecoder extends ByteToMessageDecoder {
    /**
     * 協(xié)議格式：請(qǐng)求頭 +imei號(hào) + 請(qǐng)求體
     * 請(qǐng)求頭： 指令(commond) + 版本號(hào) + clientType + 消息解析類型 + imei長(zhǎng)度 + appId + bodyLen
     *    指令：這條消息是做什么的，比如是登錄，還是群發(fā)消息，還是單聊消息，還是踢人下線....
     *    版本號(hào)：協(xié)議的版本號(hào)，對(duì)于版本升級(jí)有幫助，比如A版本的走A邏輯，B版本的走B邏輯
     *    clientType：web端，IOS，Android
     *    消息解析類型：把這條消息解析成什么樣的類型，有JSON，還是String等
     *    imei：雖然有clientType來(lái)標(biāo)識(shí)出該用戶是從WEB訪問(wèn)的還是IOS或者Android端登錄的，但是這時(shí)候有二臺(tái)IOS手機(jī)登錄你就分辨不了了
     *          所以imei號(hào)是設(shè)備的唯一標(biāo)識(shí)，這樣可以在用戶多端登錄的時(shí)候踢人下線，來(lái)實(shí)現(xiàn)一個(gè)賬號(hào)只能一臺(tái)設(shè)備登錄
     *    appId：如果我們的IM系統(tǒng)是以服務(wù)方式提供的，appId表示的是哪個(gè)服務(wù)來(lái)訪問(wèn)的
     *    bodyLen：數(shù)據(jù)長(zhǎng)度
     *  所以請(qǐng)求頭的長(zhǎng)度是：7 * 4 = 28字節(jié)
     */
    @Override
    protected void decode(ChannelHandlerContext channelHandlerContext, ByteBuf in, List<Object> out) throws Exception {
        //我們的請(qǐng)求頭有7個(gè)屬性，每個(gè)屬性都是int型，所以占4個(gè)字節(jié)，如果小于28個(gè)字節(jié)說(shuō)明這個(gè)請(qǐng)求數(shù)據(jù)是有問(wèn)題的，
        if(in.readableBytes() < 28) {
            return;
        }
        //拿到指令
        int command = in.readInt();
        //拿到版本號(hào)
        int version = in.readInt();
        //拿到clientType
        int clientType = in.readInt();
        //拿到消息解析類型
        int messageType = in.readInt();
        //拿到imei號(hào)的長(zhǎng)度
        int imeiLen = in.readInt();
        //拿到appId
        int appId = in.readInt();
        //拿到數(shù)據(jù)內(nèi)容長(zhǎng)度
        int bodyLen = in.readInt();
        //我們的數(shù)據(jù)是以流的形式讀取的，當(dāng)讀取到的數(shù)據(jù)長(zhǎng)度小于 imei號(hào)長(zhǎng)度+data長(zhǎng)度，說(shuō)明還沒(méi)有獲取到完整的請(qǐng)求數(shù)據(jù)，需要重新再次讀取接下來(lái)TCP發(fā)送過(guò)來(lái)的數(shù)據(jù)，直到等于了就代表
        //我們已經(jīng)讀取到一條完整的數(shù)據(jù)了，其實(shí)這也是一種解決TCP粘包和拆包的問(wèn)題
        if(in.readableBytes() < (bodyLen + imeiLen)) {
            //表示讀取的數(shù)據(jù)還不夠
            in.resetReaderIndex();
            return;
        }
        //通過(guò)imei號(hào)長(zhǎng)度讀取imei號(hào)
        byte[] imeiData = new byte[imeiLen];
        in.readBytes(imeiData);
        String imei = new String(imeiData);
        //通過(guò)bodyLen讀取數(shù)據(jù)內(nèi)容
        byte[] bodyData = new byte[bodyLen];
        in.readBytes(bodyData);
        /**
         * 設(shè)置請(qǐng)求頭
         */
        MessageHead messageHead = new MessageHead();
        messageHead.setCommond(command);
        messageHead.setAppId(appId);
        messageHead.setBodyLen(bodyData.length);
        messageHead.setImeiLen(imeiData.length);
        messageHead.setVersion(version);
        messageHead.setClientType(clientType);
        messageHead.setMessageType(messageType);
        /**
         * 設(shè)置請(qǐng)求體
         */
        MessageBody messageBody = new MessageBody();
        messageBody.setImei(imei);
        Message message = new Message();
        message.setMessageHead(messageHead);
        /**
         * 根據(jù)messageType來(lái)封裝請(qǐng)求數(shù)據(jù)
         */
        if(messageType == 0x0) {
            //解析成JSON格式
            String body = new String(bodyData);
            com.alibaba.fastjson.JSONObject jsonObject = new com.alibaba.fastjson.JSONObject();
            jsonObject.put("body",body);
            messageBody.setData(jsonObject);
        }else if(messageType == 0x1) {
            //解析成Protobuf
        }else if(messageType == 0x2) {
            //解析成Xml
        }
        message.setMessageBody(messageBody);
        //更新讀索引
        in.markReaderIndex();
        //最后通過(guò)管道寫出去
        out.add(message);
    }
}

package com.chat.codec;
import com.chat.model.Message;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import java.nio.charset.Charset;
public class MessageEncoder extends MessageToByteEncoder<Message> {
    @Override
    protected void encode(ChannelHandlerContext channelHandlerContext, Message message, ByteBuf out) throws Exception {
        out.writeInt(message.getMessageHead().getCommond());
        out.writeInt(message.getMessageHead().getVersion());
        out.writeInt(message.getMessageHead().getClientType());
        out.writeInt(message.getMessageHead().getMessageType());
        out.writeInt(message.getMessageBody().getImei().getBytes(Charset.forName("utf-8")).length);
        out.writeInt(message.getMessageHead().getAppId());
        out.writeInt(message.getMessageBody().getData().toString().getBytes(Charset.forName("utf-8")).length);
        out.writeBytes(message.getMessageBody().getImei().getBytes(Charset.forName("utf-8")));
        out.writeBytes(message.getMessageBody().getData().toString().getBytes(Charset.forName("utf-8")));
    }
}

package com.chat.server;
import com.chat.codec.MessageDecoder;
import com.chat.codec.MessageEncoder;
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;
public class Server {
    public static void main(String[] args) throws Exception{
        // 創(chuàng)建兩個(gè)線程組bossGroup和workerGroup, 含有的子線程N(yùn)ioEventLoop的個(gè)數(shù)默認(rèn)為cpu核數(shù)的兩倍
        // bossGroup只是處理連接請(qǐng)求 ,真正的和客戶端業(yè)務(wù)處理，會(huì)交給workerGroup完成
        EventLoopGroup bossGroup = new NioEventLoopGroup(3);
        EventLoopGroup workerGroup = new NioEventLoopGroup(8);
        try {
            // 創(chuàng)建服務(wù)器端的啟動(dòng)對(duì)象
            ServerBootstrap bootstrap = new ServerBootstrap();
            // 使用鏈?zhǔn)骄幊虂?lái)配置參數(shù)
            bootstrap.group(bossGroup, workerGroup) //設(shè)置兩個(gè)線程組
                    // 使用NioServerSocketChannel作為服務(wù)器的通道實(shí)現(xiàn)
                    .channel(NioServerSocketChannel.class)
                    // 初始化服務(wù)器連接隊(duì)列大小，服務(wù)端處理客戶端連接請(qǐng)求是順序處理的,所以同一時(shí)間只能處理一個(gè)客戶端連接。
                    // 多個(gè)客戶端同時(shí)來(lái)的時(shí)候,服務(wù)端將不能處理的客戶端連接請(qǐng)求放在隊(duì)列中等待處理
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChannelInitializer<SocketChannel>() {//創(chuàng)建通道初始化對(duì)象，設(shè)置初始化參數(shù)，在 SocketChannel 建立起來(lái)之前執(zhí)行
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new MessageDecoder());
                            ch.pipeline().addLast(new MessageEncoder());
                            ch.pipeline().addLast(new MyServerHandler());
                            //ch.pipeline().addLast(new ServerHandler());
                        }
                    });
            System.out.println("netty server start。。");
            // 綁定一個(gè)端口并且同步, 生成了一個(gè)ChannelFuture異步對(duì)象，通過(guò)isDone()等方法可以判斷異步事件的執(zhí)行情況
            // 啟動(dòng)服務(wù)器(并綁定端口)，bind是異步操作，sync方法是等待異步操作執(zhí)行完畢
            ChannelFuture cf = bootstrap.bind(9000).sync();
            // 給cf注冊(cè)監(jiān)聽(tīng)器，監(jiān)聽(tīng)我們關(guān)心的事件
            /*cf.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture future) throws Exception {
                    if (cf.isSuccess()) {
                        System.out.println("監(jiān)聽(tīng)端口9000成功");
                    } else {
                        System.out.println("監(jiān)聽(tīng)端口9000失敗");
                    }
                }
            });*/
            // 等待服務(wù)端監(jiān)聽(tīng)端口關(guān)閉，closeFuture是異步操作
            // 通過(guò)sync方法同步等待通道關(guān)閉處理完畢，這里會(huì)阻塞等待通道關(guān)閉完成，內(nèi)部調(diào)用的是Object的wait()方法
            cf.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

package com.chat.server;
import cn.hutool.json.JSONUtil;
import com.chat.model.Message;
import com.chat.model.MessageBody;
import com.chat.model.MessageHead;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class MyServerHandler extends SimpleChannelInboundHandler<Message> {
    private final static Logger logger = LoggerFactory.getLogger(MyServerHandler.class);
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Message message) throws Exception {
        System.out.println("這是客戶端發(fā)送的消息" + JSONUtil.toJsonPrettyStr(message));
        Message messageResponse = new Message();
        MessageHead messageHead = new MessageHead();
        messageHead.setCommond(9988);
        messageHead.setMessageType(0x0);
        messageHead.setClientType(1);
        messageHead.setVersion(2);
        messageHead.setAppId(3);
        String msg = "這是服務(wù)端發(fā)送給你的消息";
        messageHead.setBodyLen(msg.getBytes().length);
        String imei = "12-euri-1234";
        messageHead.setImeiLen(imei.getBytes().length);
        MessageBody messageBody = new MessageBody();
        messageBody.setImei(imei);
        messageBody.setData(msg);
        messageResponse.setMessageHead(messageHead);
        messageResponse.setMessageBody(messageBody);
        ctx.writeAndFlush(messageResponse);
    }
}

package com.chat.client;
import cn.hutool.json.JSONUtil;
import com.chat.model.Message;
import com.chat.model.MessageBody;
import com.chat.model.MessageHead;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
public class ClientHandler extends SimpleChannelInboundHandler<Message> {
    /**
     * 當(dāng)客戶端連接服務(wù)器完成就會(huì)觸發(fā)該方法
     *
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        for(int i = 0; i < 20; i ++) {
            Message message = new Message();
            MessageHead messageHead = new MessageHead();
            messageHead.setCommond(9988);
            messageHead.setMessageType(0x0);
            messageHead.setClientType(1);
            messageHead.setVersion(2);
            messageHead.setAppId(3);
            String msg = "hello-" + i;
            messageHead.setBodyLen(msg.getBytes().length);
            String imei = "12-euri";
            messageHead.setImeiLen(imei.getBytes().length);
            MessageBody messageBody = new MessageBody();
            messageBody.setImei(imei);
            messageBody.setData(msg);
            message.setMessageHead(messageHead);
            message.setMessageBody(messageBody);
            ctx.writeAndFlush(message);
        }
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
    //當(dāng)通道有讀取事件時(shí)會(huì)觸發(fā)，即服務(wù)端發(fā)送數(shù)據(jù)給客戶端
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, Message message) throws Exception {
        System.out.println(JSONUtil.toJsonPrettyStr(message));
    }
}

package com.chat.client;
import com.chat.codec.MessageDecoder;
import com.chat.codec.MessageEncoder;
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;
public class Client {
    public static void main(String[] args) throws Exception{
            //客戶端需要一個(gè)事件循環(huán)組
            EventLoopGroup group = new NioEventLoopGroup();
            try {
                //創(chuàng)建客戶端啟動(dòng)對(duì)象
                //注意客戶端使用的不是ServerBootstrap而是Bootstrap
                Bootstrap bootstrap = new Bootstrap();
                //設(shè)置相關(guān)參數(shù)
                bootstrap.group(group) //設(shè)置線程組
                        .channel(NioSocketChannel.class) // 使用NioSocketChannel作為客戶端的通道實(shí)現(xiàn)
                        .handler(new ChannelInitializer<SocketChannel>() {
                            @Override
                            protected void initChannel(SocketChannel ch) throws Exception {
                                //加入處理器
                                ch.pipeline().addLast(new MessageDecoder());
                                ch.pipeline().addLast(new MessageEncoder());
                                ch.pipeline().addLast(new ClientHandler());
                            }
                        });
                System.out.println("netty client start。。");
                //啟動(dòng)客戶端去連接服務(wù)器端
                ChannelFuture cf = bootstrap.connect("127.0.0.1", 9000).sync();
                //對(duì)通道關(guān)閉進(jìn)行監(jiān)聽(tīng)
                cf.channel().closeFuture().sync();
            } finally {
                group.shutdownGracefully();
            }
        }
}