netty实现通过私有协议的通信和探活

作者: 西5d | 来源:发表于2020-09-04 16:22 被阅读0次

背景

我们知道类似HTTP协议属于一种网络规范，包括数据结构的定义和通信规则。很多情况下，业务可能基于自身的需要，实现自有的协议，比如像Dubbo的dubbo协议。

描述

本期继续netty相关内容，这次我们根据已有例子，自己定义网络协议并完成通信。主要包括协议数据结构的定义，数据的解析和反解析，网络交互规则，而交互包括认证和心跳两部分。
下表是整体的介绍，描述各个部分的功能。

类名称	功能
Header	协议数据的头部
NettyMessage	协议数据，包括头部和数据部分
HeartbeatReqHandler	客户端处理心跳消息
HeartbeatRespHandler	服务端处理心跳消息
LoginAuthReqHandler	客户端处理登录或者握手消息
LoginAuthRespHandler	服务端处理登录或者握手消息
NettyMessageDecoder	从收到的byte字节数据解码成消息体
NettyMessageEncoder	对数据进行编码转换成byte字节发送
NettyProtocolClient	客户端实例
NettyProtocolServer	服务端实例

下面依次介绍下各个部分和包含的代码，内容会比较多。

代码

消息头结构

消息头的定义，如协议标记，用来识别协议，是个固定值。

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.Getter;
import lombok.NoArgsConstructor;

import java.util.HashMap;
import java.util.Map;

/**
 * 自定义协议的消息头
 */
@NoArgsConstructor
@Data
public class Header {
    //协议标记
    private int crcCode = 0xabef0101;
    //消息长度
    private int length;
    private long sessionId;
    //消息类型 MessageType
    private byte type;
    //优先级
    private byte priority;
    //扩展
    private Map<String, Object> attachment = new HashMap<>();

    public Header(byte type) {
        this.type = type;
    }

    //消息类型定义
    @AllArgsConstructor
    @Getter
    public enum MessageType {
        BIZ_REQ((byte) 0),
        BIZ_RESP((byte) 1),
        ONE_WAY_REQ((byte) 2),
        HANDSHAKE_REQ((byte) 3),
        HANDSHAKE_RESP((byte) 4),
        HEARTBEAT_REQ((byte) 5),
        HEARTBEAT_RESP((byte) 6),
        ;
        byte value;
    }

}

消息体结构

消息体结构比较简单，除了头部，剩下的数据用Object处理。

import lombok.Data;

/**
 * 消息结构
 */
@Data
public class NettyMessage {
    private Header header;
    private Object body;
}

消息封装(编码)

这里介绍对消息进行编码，首先处理头部，从消息对象msg中一次读取header的各项内容，然后按照顺序写入到ByteBuf中，注意根据类型的不同，使用的写入方法也是不同的。这里的ByteBuf是netty对byte[]操作的封装，如果自己实现，要麻烦很多。之后进行header.attachment的写入，因为key是string，而value是对象，所以这里我把value先转成String，然后写入大小和内容（实际操作先写入大小，再写入内容），而且因为是对象，把对象的类型提取出来，也写到后面；同样，如果消息的数据部分body不为空，采用和上面一致的方式，写入body转换后的内容大小，也写入body的类型名称。具体的也可以参照代码来处理。

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;

import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Map;

public final class NettyMessageEncoder extends MessageToMessageEncoder<NettyMessage> {
    @Override
    protected void encode(ChannelHandlerContext ctx, NettyMessage msg, List<Object> out) throws Exception {
        if (null == msg || msg.getHeader() == null) {
            throw new Exception("encode message is null!");
        }

        ByteBuf sendBuf = Unpooled.buffer();
        sendBuf.writeInt(msg.getHeader().getCrcCode())
                .writeInt(msg.getHeader().getLength())
                .writeLong(msg.getHeader().getSessionId())
                .writeByte(msg.getHeader().getType())
                .writeByte(msg.getHeader().getPriority())
                .writeInt(msg.getHeader().getAttachment().size());

        byte[] keyArray;
        byte[] valueArray;
        for (Map.Entry<String, Object> entry : msg.getHeader().getAttachment().entrySet()) {
            //写入key，先写大小，再写值，值用Gson转成String，同时把值的类型也写入
            keyArray = entry.getKey().getBytes(StandardCharsets.UTF_8);
            sendBuf.writeInt(keyArray.length);
            sendBuf.writeBytes(keyArray);
            //写值的数据，先写大小，再写内容
            valueArray = GsonUtil.toJson(entry.getValue()).getBytes(StandardCharsets.UTF_8);
            sendBuf.writeInt(valueArray.length);
            sendBuf.writeBytes(valueArray);
            //写值的类型名称
            byte[] clazzArray = entry.getValue().getClass().getName().getBytes();
            sendBuf.writeInt(clazzArray.length);
            sendBuf.writeBytes(clazzArray);
        }
        if (msg.getBody() != null) {
            byte[] bodyArray = GsonUtil.toJson(msg.getBody()).getBytes(StandardCharsets.UTF_8);
            sendBuf.writeInt(bodyArray.length);
            sendBuf.writeBytes(bodyArray);
            byte[] clazzArray = msg.getBody().getClass().getName().getBytes();
            sendBuf.writeInt(clazzArray.length);
            sendBuf.writeBytes(clazzArray);
        }
        //sendBuf.writeInt(0);
        sendBuf.setInt(4, sendBuf.readableBytes());
        out.add(sendBuf);
    }
}

消息解析(解码)

解码就相当于编码的反操作，依次按照顺序解出内容。首先是消息头部，对于对象类型的处理，是先读取对象的大小，再取内容，再取类型的大小和名称，然后通过Gson转换回java实例对象，如下的打码，可以详细了解下注释的部分。

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

public final class NettyMessageDecoder extends LengthFieldBasedFrameDecoder {

    public NettyMessageDecoder(int maxFrameLength, int lengthFieldOffset, int lengthFieldLength) {
        super(maxFrameLength, lengthFieldOffset, lengthFieldLength);
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        //        ByteBuf frame = (ByteBuf) super.decode(ctx, in);
        //        if (null == frame) {
        //            return null;
        //        }

        NettyMessage message = new NettyMessage();
        Header header = new Header();
        header.setCrcCode(in.readInt());
        header.setLength(in.readInt());
        header.setSessionId(in.readLong());
        header.setType(in.readByte());
        header.setPriority(in.readByte());

        int size = in.readInt();
        if (size > 0) {
            Map<String, Object> attch = new HashMap<>();
            int keySize;
            int valueSize;
            byte[] keyArray;
            byte[] valueArray;
            String key;
            String value;
            for (int i = 0; i < size; i++) {
                //读取长度值
                keySize = in.readInt();
                keyArray = new byte[keySize];
                //读取内容
                in.readBytes(keyArray);
                key = new String(keyArray, StandardCharsets.UTF_8);

                valueSize = in.readInt();
                valueArray = new byte[valueSize];
                in.readBytes(valueArray);
                value = new String(valueArray, StandardCharsets.UTF_8);
                int clazzSize = in.readInt();
                byte[] clazzArray = new byte[clazzSize];
                in.readBytes(clazzArray);
                String clazz = new String(clazzArray, StandardCharsets.UTF_8);
                attch.put(key, GsonUtil.parse(value, Class.forName(clazz)));
            }
            header.setAttachment(attch);
        }
        //4代表一个int，超过表示还有数据
        if (in.readableBytes() > 4) {
            //body的长度
            int bodyLength = in.readInt();
            byte[] bodyArray = new byte[bodyLength];
            //body的内容并转成String
            in.readBytes(bodyArray);
            String bodyJson = new String(bodyArray, StandardCharsets.UTF_8);
            int clazzSize = in.readInt();
            byte[] clazzArray = new byte[clazzSize];
            in.readBytes(clazzArray);
            String clazz = new String(clazzArray, StandardCharsets.UTF_8);
            //根据body的内容json和类型名称，转换成对象
            Object body = GsonUtil.parse(bodyJson, Class.forName(clazz));
            message.setBody(body);
        }
        message.setHeader(header);
        return message;
    }
}

附加-json转换

为方便直接运行代码使用，把对应的json转换也放到这里。

import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import lombok.extern.slf4j.Slf4j;

import java.util.Map;

@Slf4j
public class GsonUtil {
    private static final Gson GSON =
            new GsonBuilder().disableHtmlEscaping().setDateFormat("yyyy-MM-dd HH:mm:ss").serializeNulls().addSerializationExclusionStrategy(new ExclusionStrategy() {
                @Override
                public boolean shouldSkipField(FieldAttributes fieldAttributes) {
                    return fieldAttributes.getAnnotation(GsonIgnore.class) != null;
                }

                @Override
                public boolean shouldSkipClass(Class<?> aClass) {
                    return false;
                }
            }).create();

    public static String toJson(Object src) {
        return GSON.toJson(src);
    }

    public static <T> T parse(String str, Class<T> classOfT) {
        return GSON.fromJson(str, classOfT);
    }

    /**
     * 解析泛型
     *
     * @param json
     * @param typeToken
     * @param <T>
     * @return
     */
    public static <T> T parse(String json, TypeToken typeToken) {
        return GSON.fromJson(json, typeToken.getType());
    }
}

登录处理

客户端登录请求
客户端处理登录请求的代码，核心是在启动的时候在channelActive方法中，发送一个登录注册请求。在channelRead方法中，获取从服务端的返回，并根据协议消息的头部字段，判断类型。

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

/**
 * 客户端支持登录请求
 */
public class LoginAuthReqHandler extends ChannelInboundHandlerAdapter {

    private NettyMessage buildAuthReq() {
        NettyMessage message = new NettyMessage();
        Header header = new Header(Header.MessageType.HANDSHAKE_REQ.value);
        message.setHeader(header);
        return message;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("login auth req handler active ...");
        NettyMessage message = buildAuthReq();
        System.out.println("[send] client send login req ---> " + message);
        ctx.writeAndFlush(message);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        NettyMessage message = (NettyMessage) msg;
        if (message.getHeader() != null && message.getHeader().getType() == Header.MessageType.HANDSHAKE_RESP.value) {
            System.out.println("[recv] client receive login resp ---> " + message);
            byte loginResult = (byte) message.getBody();
            if (loginResult != (byte) 0) {
                System.out.println("handshake fail!");
                ctx.close();
            } else {
                System.out.println("handshake success.");
                ctx.fireChannelRead(msg);
            }
        } else {
            ctx.fireChannelRead(msg);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.fireExceptionCaught(cause);
    }
}

服务端登录请求
服务端对登录请求的处理，在收到消息后，判断是否是握手消息，如果是握手消息，这里加了个IP白名单的判断，如果判断成功，构造一个握手返回请求，返回给客户端。这里用body的值来判断是否握手成功。

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.net.InetSocketAddress;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 服务端处理登录握手
 */
public class LoginAuthRespHandler extends ChannelInboundHandlerAdapter {

    private Map<String, Boolean> nodeCheck = new ConcurrentHashMap<>();
    private String[] whiteList = new String[] {"127.0.0.1"};

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        NettyMessage message = (NettyMessage) msg;
        if (message.getHeader() != null && message.getHeader().getType() ==  Header.MessageType.HANDSHAKE_REQ.value) {
            String nodeIndex = ctx.channel().remoteAddress().toString();
            NettyMessage loginResp;
            if (nodeCheck.containsKey(nodeIndex)) {
                loginResp = buildResponse((byte) -1);
            } else {
                InetSocketAddress address = (InetSocketAddress) ctx.channel().remoteAddress();
                String ip = address.getAddress().getHostAddress();
                boolean ok = false;
                for (String e : whiteList) {
                    if (e.equals(ip)) {
                        ok = true;
                        break;
                    }
                }
                loginResp = ok ? buildResponse((byte) 0) : buildResponse((byte) -1);
                if (ok) {
                    nodeCheck.put(nodeIndex, true);
                }
            }
            System.out.println("[send] login response :" + loginResp + " , body:" + loginResp.getBody());
            ctx.writeAndFlush(loginResp);
        }else {
            ctx.fireChannelRead(msg);
        }
    }

    //构造握手返回请求
    private NettyMessage buildResponse(byte resp) {
        NettyMessage message = new NettyMessage();
        Header header = new Header();
        header.setType(Header.MessageType.HANDSHAKE_RESP.value);
        message.setHeader(header);
        message.setBody(resp);
        return message;
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        nodeCheck.remove(ctx.channel().remoteAddress().toString());
        ctx.close();
        ctx.fireExceptionCaught(cause);
    }
}

心跳处理

客户端心跳处理
这里看下客户端的心跳处理，有一个调度线程池，操作就是定时地发送心跳消息给服务端。同时channelRead在负责收到消息后，判断执行的操作。这里心跳是在收到握手成功的消息后开始的。注意channelAcitve方法是否执行和netty pipline中的channelHandler执行顺序有关系，比较复杂感谢的同学可以额外了解下。
这里除了在收到握手消息之后开始心跳探测，后续正常收到心跳返回包，则打印日志。

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.time.LocalDateTime;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

/**
 * 客户端处理心跳请求
 */
public class HeartbeatReqHandler extends ChannelInboundHandlerAdapter {

    private volatile ScheduledFuture<?> heartbeat;

//    @Override
//    public void channelActive(ChannelHandlerContext ctx) throws Exception {
//        System.out.println("heartbeat req channel active ...");
//        heartbeat = ctx.executor().scheduleAtFixedRate(new HeartbeatTask(ctx), 0, 5, TimeUnit.SECONDS);
//    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        NettyMessage message = (NettyMessage)msg;
        if (message.getHeader() != null) {
            //heartbeat 稍微调整下代码，因为握手比较少，心跳比较多。
            if (message.getHeader().getType() == Header.MessageType.HEARTBEAT_RESP.value) {
                System.out.println("[recv] client receive server heartbeat message ---> " + message);
            } else
                //login，握手成功以后开始客户端给服务端启动心跳
                if (message.getHeader().getType() == Header.MessageType.HANDSHAKE_RESP.value) {
                    heartbeat = ctx.executor().scheduleAtFixedRate(new HeartbeatTask(ctx), 0, 5, TimeUnit.SECONDS);
                    System.out.println("[recv] client receive server login resp, start heartbeat ---> " + message);
                }
        }
        ctx.fireChannelRead(msg);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        if (null != heartbeat) {
            heartbeat.cancel(true);
            heartbeat = null;
        }
        cause.printStackTrace();
        ctx.fireExceptionCaught(cause);
    }


    private class HeartbeatTask implements Runnable {
        private final ChannelHandlerContext ctx;
        public HeartbeatTask(final ChannelHandlerContext ctx) {
            this.ctx = ctx;
        }
        @Override
        public void run() {
            NettyMessage message = new NettyMessage();
            Header header = new Header();
            header.setType(Header.MessageType.HEARTBEAT_REQ.value);
            message.setHeader(header);
            message.setBody("heartbeat @" + LocalDateTime.now().toString() + " ...");
            System.out.println("[send] client send heartbeat to server ---> " + message);
            ctx.writeAndFlush(message);
        }
    }
}

服务端心跳处理
服务端的心跳处理就比较简单了，在收到心跳请求后，发送对等的包给客户端。

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.time.LocalDateTime;

/**
 * 服务端处理心跳请求
 */
public class HeartbeatRespHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        NettyMessage message = (NettyMessage)msg;

        if (message.getHeader() != null && message.getHeader().getType() == Header.MessageType.HEARTBEAT_REQ.value) {
            System.out.println("[recv] server received heartbeat from client ---> " + message);
            NettyMessage heartbeat = new NettyMessage();
            Header header = new Header();
            header.setType(Header.MessageType.HEARTBEAT_RESP.value);
            heartbeat.setHeader(header);
            heartbeat.setBody("heartbeat server resp @" + LocalDateTime.now());
            System.out.println("[send] server send heartbeat resp to client ---> " + heartbeat);
            ctx.writeAndFlush(heartbeat);
        }else {
            ctx.fireChannelRead(msg);
        }
    }
}

消息客户端

消息处理的客户端程序。注意有一个线程池用来做重试，这里这是简单的一次尝试重连，只做示例。其次，注意pipline的添加顺序可能影响Handler的执行结果。其他可以看下代码注释。

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.timeout.ReadTimeoutHandler;
import org.junit.Test;

import java.net.InetSocketAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class NettyProtocolClient {
    private ExecutorService executor = Executors.newFixedThreadPool(1);

    public void connect(int port, String host) {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline()
                                    .addLast(new NettyMessageDecoder(1024 * 1024, 4, 4))
                                    .addLast(new NettyMessageEncoder())
                                    .addLast(new ReadTimeoutHandler(50))
                                    .addLast(new LoginAuthReqHandler())
                                    .addLast(new HeartbeatReqHandler());
                        }
                    });

            final String localhost = "127.0.0.1";
            final int localPort = 1922;
            //如果加了本地地址和端口，相当于固定了本地端口，如果停止后立刻再次登录，由于之前请求会保留TIME_WAIT状态socket一段时间，会抛出Caused by: java.net.BindException: 地址已在使用
            //没有设置本地端口，每次本地端口是新生成的，短时间内立即请求会消耗大量系统连接资源
            System.out.println("client connect @" + host + ":" + port);
            //注意用了两个sync，没有channelFuture可能不会抛出异常
            ChannelFuture future =
                    bootstrap.connect(new InetSocketAddress(host, port), new InetSocketAddress(localhost, localPort)).sync().channel().closeFuture().sync();
            future.channel().closeFuture().sync();
            //不会抛异常
            //bootstrap.connect(new InetSocketAddress(host, port), new InetSocketAddress(localhost, localPort)).channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
            //资源释放后，清空，然后发起重连
            //这里加了强制等待线程执行1分钟，否则是直接退出的。
            executor.execute(() -> {
                try {
                    int timeout = 15;
                    System.out.println("retry connect after :" + timeout);
                    TimeUnit.SECONDS.sleep(timeout);
                    try {
                        System.out.println("retry connect ...");
                        connect(port, host);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
            if (!executor.isTerminated()) {
                try {
                    executor.awaitTermination(1, TimeUnit.MINUTES);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Test
    public void runClient() {
        int port = 12342;
        String host = "127.0.0.1";
        connect(port, host);
    }
}

消息服务端

服务端相对要简单一些，添加各个EventLoopGroup之后，追加自定的消息解析器和协议handler，绑定指定端口启动就可以接收情趣了。

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.ReadTimeoutHandler;
import org.junit.Test;

public class NettyProtocolServer {
    private void bind(int port) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        ServerBootstrap bootstrap = new ServerBootstrap();

        try {
            bootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 100)
                    .handler(new LoggingHandler(LogLevel.DEBUG))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline()
                                    .addLast(new NettyMessageDecoder(1024 * 1024, 4, 4))
                                    .addLast(new NettyMessageEncoder())
                                    .addLast(new ReadTimeoutHandler(60))
                                    .addLast(new LoginAuthRespHandler())
                                    .addLast(new HeartbeatRespHandler());
                        }
                    });
            System.out.println("netty protocol server@" + port);
            bootstrap.bind(port).channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

    @Test
    public void runServer() throws InterruptedException {
        bind(12342);
    }
}

运行结果

服务端

netty protocol server@12342
[send] login response :NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=4, priority=0, attachment={}), body=0) , body:0
[recv] server received heartbeat from client ---> NettyMessage(header=Header(crcCode=-1410399999, length=86, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:19:58.102 ...)
[send] server send heartbeat resp to client ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:19:58.118)
[recv] server received heartbeat from client ---> NettyMessage(header=Header(crcCode=-1410399999, length=86, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:20:03.089 ...)
[send] server send heartbeat resp to client ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:20:03.091)
[recv] server received heartbeat from client ---> NettyMessage(header=Header(crcCode=-1410399999, length=86, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:20:08.090 ...)
[send] server send heartbeat resp to client ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:20:08.091)

客户端

client connect @127.0.0.1:12342
login auth req handler active ...
[send] client send login req ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=3, priority=0, attachment={}), body=null)
[recv] client receive login resp ---> NettyMessage(header=Header(crcCode=-1410399999, length=45, sessionId=0, type=4, priority=0, attachment={}), body=0)
handshake success.
[recv] client receive server login resp, start heartbeat ---> NettyMessage(header=Header(crcCode=-1410399999, length=45, sessionId=0, type=4, priority=0, attachment={}), body=0)
[send] client send heartbeat to server ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:19:58.102 ...)
[recv] client receive server heartbeat message ---> NettyMessage(header=Header(crcCode=-1410399999, length=94, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:19:58.118)
[send] client send heartbeat to server ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:20:03.089 ...)
[recv] client receive server heartbeat message ---> NettyMessage(header=Header(crcCode=-1410399999, length=94, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:20:03.091)
[send] client send heartbeat to server ---> NettyMessage(header=Header(crcCode=-1410399999, length=0, sessionId=0, type=5, priority=0, attachment={}), body=heartbeat @2020-09-04T16:20:08.090 ...)
[recv] client receive server heartbeat message ---> NettyMessage(header=Header(crcCode=-1410399999, length=94, sessionId=0, type=6, priority=0, attachment={}), body=heartbeat server resp @2020-09-04T16:20:08.091)

client

server

总结

以上就是本期的内容，netty确实在网络处理方面比较强大，能够比较容易地在其基础上实现各种网络组件，比自己从头开发要方便很多。本期也参考了书本和网络的知识（书之前吐槽过），在官方的github没有找到本期内容的示例，有篇文章但功能不是很完善。后面会给到所有的参考链接。

参考资料

[1]. netty example
[2]. 《netty权威指南》私有协议

netty实现通过私有协议的通信和探活

背景

描述

代码

消息头结构

消息体结构

消息封装(编码)

消息解析(解码)

附加-json转换

登录处理

心跳处理

消息客户端

消息服务端

运行结果

服务端

客户端

总结

参考资料

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