Netty从入门到进阶（三）

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已于 2025-06-15 14:49:47 修改

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分类专栏： Netty网络编程文章标签： java Netty网络编程

于 2025-06-10 22:35:44 首次发布

本文链接：https://blog.youkuaiyun.com/ltt159264/article/details/148538103

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三、Netty进阶

1. 粘包与半包

1.1 粘包现象

服务器端：

package cn.itcast.netty.c3_1;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
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 org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HelloWorldServer {

    static final Logger log = LoggerFactory.getLogger(HelloWorldServer.class);

    void start() {
        NioEventLoopGroup boss = new NioEventLoopGroup(1);
        NioEventLoopGroup worker = new NioEventLoopGroup();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.group(boss, worker);
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        // 会在连接channel 建立成功后，触发active事件
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("connected {}", ctx.channel());
                            super.channelActive(ctx);
                        }

                        @Override
                        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("disconnect {}", ctx.channel());
                            super.channelInactive(ctx);
                        }
                    });
                }
            });

            ChannelFuture channelFuture = serverBootstrap.bind(8080);
            log.debug("{} binding...", channelFuture.channel());
            channelFuture.sync();
            log.debug("{} bound...", channelFuture.channel());
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("server error: ", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
            log.debug("stoped");
        }
    }

    public static void main(String[] args) {
        new HelloWorldServer().start();
    }
}

客户端：发送10条消息，每条消息是16字节

package cn.itcast.netty.c3_1;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Random;

public class HelloWorldClient {
    static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);

    public static void main(String[] args) {
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    log.debug("connected...");
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("sending...");
                            Random r = new Random();
                            char c = 'a';
                            for (int i = 0; i < 10; i++) {
                                ByteBuf buffer = ctx.alloc().buffer(16);
                                buffer.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
                                ctx.writeAndFlush(buffer);
                            }
                        }
                    });
                }
            });

            ChannelFuture channelFuture = bootstrap.connect("localhost", 8080).sync();
            channelFuture.channel().closeFuture().sync();  // 阻塞当前线程，直到服务器的 Channel 关闭
        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            worker.shutdownGracefully();
        }
    }
}

服务器端的输出：可以看到一次就接收了160个字节，而非分10次接收

20:35:03 [DEBUG] [main] c.i.n.c.HelloWorldServer - [id: 0x287df118] binding...
20:35:03 [DEBUG] [main] c.i.n.c.HelloWorldServer - [id: 0x287df118, L:/0:0:0:0:0:0:0:0:8080] bound...
20:35:08 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x98f26176, L:/127.0.0.1:8080 - R:/127.0.0.1:58016] REGISTERED
20:35:08 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x98f26176, L:/127.0.0.1:8080 - R:/127.0.0.1:58016] ACTIVE
20:35:08 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.c.HelloWorldServer - connected [id: 0x98f26176, L:/127.0.0.1:8080 - R:/127.0.0.1:58016]
20:35:08 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x98f26176, L:/127.0.0.1:8080 - R:/127.0.0.1:58016] READ: 160B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000010| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000020| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000030| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000040| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000050| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000060| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000070| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000080| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000090| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
+--------+-------------------------------------------------+----------------+
20:35:08 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x98f26176, L:/127.0.0.1:8080 - R:/127.0.0.1:58016] READ COMPLETE

1.2 半包现象

客户端希望发送1条消息，这条消息是160字节，代码改为：

ByteBuf buffer = ctx.alloc().buffer();
for (int i = 0; i < 10; i++) {
    buffer.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
}
ctx.writeAndFlush(buffer);

为现象明显，服务器端修改一下接收缓冲区：

serverBootstrap.option(ChannelOption.SO_RCVBUF, 10);

服务器端的某次输出，可以看到接收的消息被分为两节，第一次20字节，第二次140字节：

20:44:28 [DEBUG] [main] c.i.n.c.HelloWorldServer - [id: 0xe5372d68] binding...
20:44:28 [DEBUG] [main] c.i.n.c.HelloWorldServer - [id: 0xe5372d68, L:/0:0:0:0:0:0:0:0:8080] bound...
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] REGISTERED
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] ACTIVE
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.c.HelloWorldServer - connected [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415]
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] READ: 20B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
|00000010| 00 01 02 03 |.... |
+--------+-------------------------------------------------+----------------+
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] READ COMPLETE
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] READ: 140B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000010| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000020| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000030| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000040| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000050| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000060| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000070| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
|00000080| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |............ |
+--------+-------------------------------------------------+----------------+
20:44:31 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xfe460877, L:/127.0.0.1:8080 - R:/127.0.0.1:58415] READ COMPLETE

注意：serverBootstrap.option(ChannelOption.SO_RCVBUF, 10)影响的是底层接收缓冲区（即滑动窗口）大小，仅决定了netty读取的最小单位，netty实际每次读取的一般是它的整数倍。

1.3 现象分析

粘包

现象：发送 abc def，接收 abcdef
原因：
- 应用层：接收方ByteBuf设置太大（Netty默认1024）
- 滑动窗口：假设发送方256bytes表示一个完整报文，但由于接收方处理不及时且窗口大小足够大，这256bytes就会缓冲在接收方的滑动窗口中，当滑动窗口中缓冲了多个报文就会粘包
- Nagle算法：会造成粘包

半包

现象：发送 abcdef，接收 abc def
原因：
- 应用层：接收方ByteBuf小于实际发送数据量
- 滑动窗口：假设接收方的窗口只剩了128bytes，发送方的报文大小是256bytes，这时放不下了，只能先发送前128bytes，等待ack后才能发送剩余部分，这就造成了半包；
- MSS限制：当发送的数据超过MSS限制后，会将数据切换发送，就会造成半包

本质是因为TCP是流式协议，消息无边界。

滑动窗口

TCP以一个段（segment）为单位，每发送一个段就需要进行一次确认应答（ack）处理，但如果这么做，缺点是包的往返时间越长性能就越差。

为了解决此问题，引入了窗口概念，窗口大小即决定了无需等待应答而可以继续发送的数据最大值。

窗口实际就起到一个缓冲区的作用，同时也能起到流量控制的作用

窗口内的数据才允许被发送，当应答未到达前，窗口必须停止滑动
如果窗口内的数据ack回来了，窗口就可以向前滑动
接收方也会维护一个窗口，只有落在窗口内的数据才能允许接收

MSS限制

链路层对一次能够发送的最大数据有限制，这个限制称之为MTU（maximum transmission unit），不同的链路设备的MTU值也有所不同，例如：

以太网的MTU是1500
FDDI（光纤分布式数据接口）的MTU是4352
本地回环地址的MTU是65535（本地测试不走网卡）
MSS是最大段长度（maximum segment size），它是MTU刨去tcp头和ip头后剩余能够作为数据传输的字节数
ipv4 tcp头占用20bytes，ip头占用20bytes，因此以太网MSS的值为1500 - 40 - 1460
TCP在传递大量数据时，会按照MSS大小将数据进行分割发送
MSS的值在三次握手时会通知对方自己的MSS值，然后在两者之间选择一个小值作为MSS

Nagle算法

即使发送一个字节，也需要加入tcp头和ip头，也就是总字节数会使用41bytes，非常不经济。因此，为了提高网络利用率，tcp希望尽可能发送足够大的数据，这就是Nagle算法产生的缘由。
该算法是指发送端即使还有应该发送的数据，但如果这部分数据很少的话，则进行延迟发送
- 如果SO_SNDBUF的数据达到MSS，则需要发送
- 如果SO_SNDBUF中含有FIN（表示需要连接关闭），这时将剩余数据发送，再关闭
- 如果TCP_NODELAY = true，则需要发送
- 已发送的数据都收到ack时，则需要发送
- 上述条件不满足，但发生超时（一般为200ms），则需要发生
- 除上述情况，延迟发生

1.4 解决方案

1. 短连接：发生一个包建立一次连接，这样连接建立到连接断开之间就是消息的边界，缺点是效率太低；

2. 每一条消息采用固定长度，缺点是浪费空间；

3. 每一条消息采用分隔符，例如 \n，缺点是需要转义；

4. 每一条消息分为head和body，head中包含body的长度

方法1：短连接

以解决粘包为例：

public class HelloWorldClient {
    static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);

    public static void main(String[] args) {
        // 分 10 次发送
        for (int i = 0; i < 10; i++) {
            send();
        }
    }

    private static void send() {
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    log.debug("conneted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("sending...");
                            ByteBuf buffer = ctx.alloc().buffer();
                            buffer.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
                            ctx.writeAndFlush(buffer);
                            // 发完即关
                            ctx.close();
                        }
                    });
                }
            });
            ChannelFuture channelFuture = bootstrap.connect("localhost", 8080).sync();
            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            worker.shutdownGracefully();
        }
    }
}

半包用这种方法还是不好解决，因为接收方的缓冲区大小是有限的。

方法2：固定长度

让所有数据包长度固定（假设长度为8字节），HelloWorldServer 服务器端加入：

ch.pipeline().addLast(new FixedLengthFrameDecoder(8));

注意：放在ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG))之前

客户端代码：注意，采用这种方法后，客户端什么时候flush都可以

public class HelloWorldClient {
    static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);

    public static void main(String[] args) {
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    log.debug("connetted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("sending...");
                            // 发送内容随机的数据包
                            Random r = new Random();
                            char c = 'a';
                            ByteBuf buffer = ctx.alloc().buffer();
                            for (int i = 0; i < 10; i++) {
                                byte[] bytes = new byte[8];
                                for (int j = 0; j < r.nextInt(8); j++) {
                                    bytes[j] = (byte) c;
                                }
                                c++;
                                buffer.writeBytes(bytes);
                            }
                            ctx.writeAndFlush(buffer);
                        }
                    });
                }
            });
            ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            worker.shutdownGracefully();
        }
    }
}

客户端输出

12:07:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2] REGISTERED
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2] CONNECT: /192.168.0.103:9090
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2, L:/192.168.0.103:53155 - R:/192.168.0.103:9090] ACTIVE
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2, L:/192.168.0.103:53155 - R:/192.168.0.103:9090] WRITE: 80B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 61 61 61 00 00 00 00 62 00 00 00 00 00 00 00 |aaaa....b.......|
|00000010| 63 63 00 00 00 00 00 00 64 00 00 00 00 00 00 00 |cc......d.......|
|00000020| 00 00 00 00 00 00 00 00 66 66 66 66 00 00 00 00 |........ffff....|
|00000030| 67 67 67 00 00 00 00 00 68 00 00 00 00 00 00 00 |ggg.....h.......|
|00000040| 69 69 69 69 69 00 00 00 6a 6a 6a 6a 00 00 00 00 |iiiii...jjjj....|
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2, L:/192.168.0.103:53155 - R:/192.168.0.103:9090] FLUSH

服务端输出

12:06:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xe3d9713f] binding...
12:06:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xe3d9713f, L:/192.168.0.103:9090] bound...
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] REGISTERED
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] ACTIVE
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.HelloWorldServer - connected [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155]
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 61 61 61 00 00 00 00 |aaaa.... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 62 00 00 00 00 00 00 00 |b....... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 63 63 00 00 00 00 00 00 |cc...... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 64 00 00 00 00 00 00 00 |d....... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 00 00 00 00 00 00 00 |........ |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 66 66 66 66 00 00 00 00 |ffff.... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 67 67 67 00 00 00 00 00 |ggg..... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 00 00 00 00 00 00 00 |h....... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 69 69 69 69 69 00 00 00 |iiiii... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 6a 6a 6a 6a 00 00 00 00 |jjjj.... |
+--------+-------------------------------------------------+----------------+
12:07:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd739f137, L:/192.168.0.103:9090 - R:/192.168.0.103:53155] READ COMPLETE

缺点是，数据包的大小不好把握

长度定的太大，浪费
长度定的太小，对某些数据包又显得不够

方法3：固定分隔符

服务端加入：（默认以 \n 或 \r\n 作为分隔符，如果超出指定长度仍未出现分隔符，则抛出异常）

ch.pipeline().addLast(new LineBasedFrameDecoder(1024));

客户端在每条消息之后，加入 \n 分隔符

public class HelloWorldClient {
    static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);

    public static void main(String[] args) {
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    log.debug("connetted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("sending...");
                            Random r = new Random();
                            char c = 'a';
                            ByteBuf buffer = ctx.alloc().buffer();
                            for (int i = 0; i < 10; i++) {
                                for (int j = 1; j <= r.nextInt(16)+1; j++) {
                                    buffer.writeByte((byte) c);
                                }
                                buffer.writeByte(10);  // 加入换行符
                                c++;
                            }
                            ctx.writeAndFlush(buffer);
                        }
                    });
                }
            });
            ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            worker.shutdownGracefully();
        }
    }
}

客户端输出

14:08:18 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755] REGISTERED
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755] CONNECT: /192.168.0.103:9090
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755, L:/192.168.0.103:63641 - R:/192.168.0.103:9090] ACTIVE
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755, L:/192.168.0.103:63641 - R:/192.168.0.103:9090] WRITE: 60B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 0a 62 62 62 0a 63 63 63 0a 64 64 0a 65 65 65 |a.bbb.ccc.dd.eee|
|00000010| 65 65 65 65 65 65 65 0a 66 66 0a 67 67 67 67 67 |eeeeeee.ff.ggggg|
|00000020| 67 67 0a 68 68 68 68 0a 69 69 69 69 69 69 69 0a |gg.hhhh.iiiiiii.|
|00000030| 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 0a |jjjjjjjjjjj. |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755, L:/192.168.0.103:63641 - R:/192.168.0.103:9090] FLUSH

注：其中红色的点就是换行符。

服务端输出：

14:08:18 [DEBUG] [nioEventLoopGroup-3-5] c.i.n.HelloWorldServer - connected [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641]
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 1B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 |a |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 3B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 62 62 62 |bbb |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 3B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 63 63 63 |ccc |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 2B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 64 64 |dd |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 10B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 65 65 65 65 65 65 65 65 65 65 |eeeeeeeeee |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 2B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 66 66 |ff |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 7B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 67 67 67 67 67 67 67 |ggggggg |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 4B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 68 68 68 |hhhh |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 7B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 69 69 69 69 69 69 69 |iiiiiii |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ: 11B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a |jjjjjjjjjjj |
+--------+-------------------------------------------------+----------------+
14:08:18 [DEBUG] [nioEventLoopGroup-3-5] i.n.h.l.LoggingHandler - [id: 0xa4b3be43, L:/192.168.0.103:9090 - R:/192.168.0.103:63641] READ COMPLETE

方法4：预设长度

在发送消息前，先约定用定长字节表示接下来的数据的长度

// 最大长度，长度偏移，长度占用字节，长度调整，剥离字节数
ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(1024, 0, 1, 0, 1));

客户端代码：

public class HelloWorldClient {
    static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);

    public static void main(String[] args) {
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    log.debug("connetted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            log.debug("sending...");
                            Random r = new Random();
                            char c = 'a';
                            ByteBuf buffer = ctx.alloc().buffer();
                            for (int i = 0; i < 10; i++) {
                                byte length = (byte) (r.nextInt(16) + 1);
                                // 先写入内容长度
                                buffer.writeByte(length);
                                // 再写入内容
                                for (int j = 1; j <= length; j++) {
                                    buffer.writeByte((byte) c);
                                }
                                c++;
                            }
                            ctx.writeAndFlush(buffer);
                        }
                    });
                }
            });
            ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            worker.shutdownGracefully();
        }
    }
}

客户端输出：

14:37:10 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8] REGISTERED
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8] CONNECT: /192.168.0.103:9090
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8, L:/192.168.0.103:49979 - R:/192.168.0.103:9090] ACTIVE
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8, L:/192.168.0.103:49979 - R:/192.168.0.103:9090] WRITE: 97B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 09 61 61 61 61 61 61 61 61 61 09 62 62 62 62 62 |.aaaaaaaaa.bbbbb|
|00000010| 62 62 62 62 06 63 63 63 63 63 63 08 64 64 64 64 |bbbb.cccccc.dddd|
|00000020| 64 64 64 64 0f 65 65 65 65 65 65 65 65 65 65 65 |dddd.eeeeeeeeeee|
|00000030| 65 65 65 65 0d 66 66 66 66 66 66 66 66 66 66 66 |eeee.fffffffffff|
|00000040| 66 66 02 67 67 02 68 68 0e 69 69 69 69 69 69 69 |ff.gg.hh.iiiiiii|
|00000050| 69 69 69 69 69 69 69 09 6a 6a 6a 6a 6a 6a 6a 6a |iiiiiii.jjjjjjjj|
|00000060| 6a |j |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8, L:/192.168.0.103:49979 - R:/192.168.0.103:9090] FLUSH

服务端输出：

14:36:50 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xdff439d3] binding...
14:36:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xdff439d3, L:/192.168.0.103:9090] bound...
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] REGISTERED
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] ACTIVE
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.HelloWorldServer - connected [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979]
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 9B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 61 61 61 61 61 61 61 61 |aaaaaaaaa |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 9B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 62 62 62 62 62 62 62 62 62 |bbbbbbbbb |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 6B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 63 63 63 63 63 63 |cccccc |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 8B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 64 64 64 64 64 64 64 64 |dddddddd |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 15B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 |eeeeeeeeeeeeeee |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 13B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 66 66 66 66 66 66 66 66 66 66 66 66 66 |fffffffffffff |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 2B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 67 67 |gg |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 2B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 68 |hh |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 14B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 69 69 69 69 69 69 69 69 69 69 69 69 69 69 |iiiiiiiiiiiiii |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ: 9B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 6a 6a 6a 6a 6a 6a 6a 6a 6a |jjjjjjjjj |
+--------+-------------------------------------------------+----------------+
14:37:10 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x744f2b47, L:/192.168.0.103:9090 - R:/192.168.0.103:49979] READ COMPLETE

2. 协议设计与解析

2.1 为什么需要协议

TCP/IP中消息传输基于流的方式，没有边界。

协议的目的就是划定消息的边界，制定通信双方要共同遵守的通信规则。

例如：在网络上传输

下雨天留客天留我不留

是中文一句著名的无标点符号句子，在没有标点符号情况下，这句话有数种拆解方式，而意思却是完全不同，所以常被用作讲述标点符号的重要性。

一种解读

下雨天留客，天留，我不留

另一种解读

下雨天，留客天，留我不？留

如何设计协议呢？其实就是给网络传输的信息加上“标点符号”。但通过分隔符来断句不是很好，因为分隔符本身如果用于传输，那么必须加以区分。因此，下面一种协议较为常见

定长字节表示内容长度 + 实际内容

例如，假设一个中文字符长度为3，按照上述协议的规则，发送消息方式如下，就不会被接收方弄错意思了

0f下雨天留客06天留09我不留

2.2 redis协议举例

package cn.itcast.netty.c3_1;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

import java.nio.charset.Charset;

@Slf4j
public class TestRedis {
    /*
        set name zhangsan
        *3
        $3
        set
        $4
        name
        $8
        zhangsan
     */
    public static void main(String[] args) {
        final byte[] LINE = {13, 10};  // \r\n
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new LoggingHandler());
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            ByteBuf buf = ctx.alloc().buffer();
                            buf.writeBytes("*3".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("$3".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("set".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("$4".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("name".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("$8".getBytes());
                            buf.writeBytes(LINE);
                            buf.writeBytes("zhangsan".getBytes());
                            buf.writeBytes(LINE);

                            ctx.writeAndFlush(buf);
                        }

                        @Override
                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                            ByteBuf buf = (ByteBuf) msg;
                            System.out.println(buf.toString(Charset.defaultCharset()));
                        }
                    });
                }
            });

            ChannelFuture channelFuture = bootstrap.connect("localhost", 6379).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("client error", e);
        }
    }
}

输出

09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9] REGISTERED
09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9] CONNECT: localhost/127.0.0.1:6379
09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9, L:/127.0.0.1:50529 - R:localhost/127.0.0.1:6379] ACTIVE
09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9, L:/127.0.0.1:50529 - R:localhost/127.0.0.1:6379] WRITE: 37B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 2a 33 0d 0a 24 33 0d 0a 73 65 74 0d 0a 24 34 0d |*3..$3..set..$4.|
|00000010| 0a 6e 61 6d 65 0d 0a 24 38 0d 0a 7a 68 61 6e 67 |.name..$8..zhang|
|00000020| 73 61 6e 0d 0a |san.. |
+--------+-------------------------------------------------+----------------+
09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9, L:/127.0.0.1:50529 - R:localhost/127.0.0.1:6379] FLUSH
09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9, L:/127.0.0.1:50529 - R:localhost/127.0.0.1:6379] READ: 5B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 2b 4f 4b 0d 0a |+OK.. |
+--------+-------------------------------------------------+----------------+
+OK

09:13:19 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xe0e802c9, L:/127.0.0.1:50529 - R:localhost/127.0.0.1:6379] READ COMPLETE

2.3 http协议举例

package cn.itcast.netty.c3_1;

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.http.*;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

import static com.google.common.net.HttpHeaders.CONTENT_LENGTH;

@Slf4j
public class TestHttp {
    public static void main(String[] args) {
        NioEventLoopGroup boss = new NioEventLoopGroup();
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.channel(NioServerSocketChannel.class);
            bootstrap.group(boss, worker);
            bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new HttpServerCodec());
                    ch.pipeline().addLast(new SimpleChannelInboundHandler<HttpRequest>() {
                        @Override
                        protected void channelRead0(ChannelHandlerContext ctx, HttpRequest msg) throws Exception {
                            log.debug(msg.uri());  // 获取请求
                            // log.debug(msg.headers());

                            // 返回响应
                            DefaultFullHttpResponse response = new DefaultFullHttpResponse(msg.protocolVersion(), HttpResponseStatus.OK);
                            byte[] bytes = "<h1>Hello, world!</h1>".getBytes();
                            response.headers().setInt(CONTENT_LENGTH, bytes.length);
                            response.content().writeBytes(bytes);

                            // 写回响应
                            ctx.writeAndFlush(response);
                        }
                    });
                    /*ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
                        @Override
                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                            log.debug("{}", msg.getClass());

                            if (msg instanceof HttpRequest) {  // 请求行、请求体

                            } else if (msg instanceof HttpContent) {  // 请求体

                            }
                        }
                    });*/
                }
            });

            ChannelFuture channelFuture = bootstrap.bind(8080).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }
}

输出

09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] REGISTERED
09:40:36 [DEBUG] [nioEventLoopGroup-3-2] i.n.h.l.LoggingHandler - [id: 0x5f77996c, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51848] REGISTERED
09:40:36 [DEBUG] [nioEventLoopGroup-3-2] i.n.h.l.LoggingHandler - [id: 0x5f77996c, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51848] ACTIVE
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] ACTIVE
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] READ: 619B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 47 45 54 20 2f 69 6e 64 65 78 2e 68 74 6d 6c 20 |GET /index.html |
|00000010| 48 54 54 50 2f 31 2e 31 0d 0a 48 6f 73 74 3a 20 |HTTP/1.1..Host: |
|00000020| 6c 6f 63 61 6c 68 6f 73 74 3a 38 30 38 30 0d 0a |localhost:8080..|
|00000030| 43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 6b 65 65 70 |Connection: keep|
|00000040| 2d 61 6c 69 76 65 0d 0a 73 65 63 2d 63 68 2d 75 |-alive..sec-ch-u|
|00000050| 61 3a 20 22 43 68 72 6f 6d 69 75 6d 22 3b 76 3d |a: "Chromium";v=|
|00000060| 22 31 22 2c 20 22 20 4e 6f 74 3b 41 20 42 72 61 |"1", " Not;A Bra|
|00000070| 6e 64 22 3b 76 3d 22 39 39 22 0d 0a 73 65 63 2d |nd";v="99"..sec-|
|00000080| 63 68 2d 75 61 2d 6d 6f 62 69 6c 65 3a 20 3f 30 |ch-ua-mobile: ?0|
|00000090| 0d 0a 55 70 67 72 61 64 65 2d 49 6e 73 65 63 75 |..Upgrade-Insecu|
|000000a0| 72 65 2d 52 65 71 75 65 73 74 73 3a 20 31 0d 0a |re-Requests: 1..|
|000000b0| 55 73 65 72 2d 41 67 65 6e 74 3a 20 4d 6f 7a 69 |User-Agent: Mozi|
|000000c0| 6c 6c 61 2f 35 2e 30 20 28 57 69 6e 64 6f 77 73 |lla/5.0 (Windows|
|000000d0| 20 4e 54 20 31 30 2e 30 3b 20 57 4f 57 36 34 29 | NT 10.0; WOW64)|
|000000e0| 20 41 70 70 6c 65 57 65 62 4b 69 74 2f 35 33 37 | AppleWebKit/537|
|000000f0| 2e 33 36 20 28 4b 48 54 4d 4c 2c 20 6c 69 6b 65 |.36 (KHTML, like|
|00000100| 20 47 65 63 6b 6f 29 20 43 68 72 6f 6d 65 2f 39 | Gecko) Chrome/9|
|00000110| 30 2e 30 2e 34 34 33 30 2e 32 32 32 20 53 61 66 |0.0.4430.222 Saf|
|00000120| 61 72 69 2f 35 33 37 2e 33 36 0d 0a 41 63 63 65 |ari/537.36..Acce|
|00000130| 70 74 3a 20 74 65 78 74 2f 68 74 6d 6c 2c 61 70 |pt: text/html,ap|
|00000140| 70 6c 69 63 61 74 69 6f 6e 2f 78 68 74 6d 6c 2b |plication/xhtml+|
|00000150| 78 6d 6c 2c 61 70 70 6c 69 63 61 74 69 6f 6e 2f |xml,application/|
|00000160| 78 6d 6c 3b 71 3d 30 2e 39 2c 69 6d 61 67 65 2f |xml;q=0.9,image/|
|00000170| 61 76 69 66 2c 69 6d 61 67 65 2f 77 65 62 70 2c |avif,image/webp,|
|00000180| 69 6d 61 67 65 2f 61 70 6e 67 2c 2a 2f 2a 3b 71 |image/apng,*/*;q|
|00000190| 3d 30 2e 38 2c 61 70 70 6c 69 63 61 74 69 6f 6e |=0.8,application|
|000001a0| 2f 73 69 67 6e 65 64 2d 65 78 63 68 61 6e 67 65 |/signed-exchange|
|000001b0| 3b 76 3d 62 33 3b 71 3d 30 2e 39 0d 0a 53 65 63 |;v=b3;q=0.9..Sec|
|000001c0| 2d 46 65 74 63 68 2d 53 69 74 65 3a 20 6e 6f 6e |-Fetch-Site: non|
|000001d0| 65 0d 0a 53 65 63 2d 46 65 74 63 68 2d 4d 6f 64 |e..Sec-Fetch-Mod|
|000001e0| 65 3a 20 6e 61 76 69 67 61 74 65 0d 0a 53 65 63 |e: navigate..Sec|
|000001f0| 2d 46 65 74 63 68 2d 55 73 65 72 3a 20 3f 31 0d |-Fetch-User: ?1.|
|00000200| 0a 53 65 63 2d 46 65 74 63 68 2d 44 65 73 74 3a |.Sec-Fetch-Dest:|
|00000210| 20 64 6f 63 75 6d 65 6e 74 0d 0a 41 63 63 65 70 | document..Accep|
|00000220| 74 2d 45 6e 63 6f 64 69 6e 67 3a 20 67 7a 69 70 |t-Encoding: gzip|
|00000230| 2c 20 64 65 66 6c 61 74 65 2c 20 62 72 0d 0a 41 |, deflate, br..A|
|00000240| 63 63 65 70 74 2d 4c 61 6e 67 75 61 67 65 3a 20 |ccept-Language: |
|00000250| 65 6e 2c 7a 68 2d 43 4e 3b 71 3d 30 2e 39 2c 7a |en,zh-CN;q=0.9,z|
|00000260| 68 3b 71 3d 30 2e 38 0d 0a 0d 0a |h;q=0.8.... |
+--------+-------------------------------------------------+----------------+
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.c.TestHttp - /index.html
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] WRITE: 61B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
|00000010| 0a 43 6f 6e 74 65 6e 74 2d 4c 65 6e 67 74 68 3a |.Content-Length:|
|00000020| 20 32 32 0d 0a 0d 0a 3c 68 31 3e 48 65 6c 6c 6f | 22....<h1>Hello|
|00000030| 2c 20 77 6f 72 6c 64 21 3c 2f 68 31 3e |, world!</h1> |
+--------+-------------------------------------------------+----------------+
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] FLUSH
09:40:36 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x0862755d, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:51847] READ COMPLETE

2.4 自定义协议要素

魔数，用来在第一时间判定是否是无效数据包
版本号，可以支持协议的升级
序列化算法，消息正文到底采用哪种序列化反序列化方式，可以由此扩展，例如：json、protobuf、hessian、jdk
指令类型，是登录、注册、单聊、群聊... 跟业务相关
请求序号，为了双工通信，提供异步能力
正文长度
消息正文

编解码器

根据上面的要素，设计一个登录请求消息和登录响应消息，并使用Netty完成收发

package cn.itcast.protocol;

import cn.itcast.message.Message;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageCodec;
import lombok.extern.slf4j.Slf4j;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.List;

@Slf4j
// ByteToMessageCodec默认不能共享
public class MessageCodec extends ByteToMessageCodec<Message> {

    @Override
    protected void encode(ChannelHandlerContext ctx, Message msg, ByteBuf out) throws Exception {
        // 1. 4个字节的魔数
        out.writeBytes(new byte[]{1, 2, 3, 4});
        // 2. 1个字节的版本号
        out.writeByte(1);
        // 3. 1个字节的序列化方式 jdk 0, json 1
        out.writeByte(0);
        // 4. 1个字节的指令类型
        out.writeByte(msg.getMessageType());
        // 5. 4个字节的请求序号
        out.writeInt(msg.getSequenceId());
        // 无意义，字节对齐填充
        out.writeByte(0xff);
        // 6. 获取内容的字节数组
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream outputStream = new ObjectOutputStream(bos);
        outputStream.writeObject(msg);
        byte[] bytes = bos.toByteArray();
        // 7. 正文长度
        out.writeInt(bytes.length);
        // 8. 消息正文
        out.writeBytes(bytes);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        // 1. 魔数
        int magicNum = in.readInt();
        // 2. 版本号
        byte version = in.readByte();
        // 3. 序列化方式
        byte serializerType = in.readByte();
        // 4. 字节的指令类型
        byte messageType = in.readByte();
        // 5. 序号
        int sequenceId = in.readInt();
        // 无意义填充字节
        in.readByte();
        // 6. 长度
        int length = in.readInt();
        // 7. 内容
        byte[] bytes = new byte[length];
        in.readBytes(bytes, 0, length);

        ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bytes));
        Message message = (Message) ois.readObject();
        log.debug("{}, {}, {}, {}, {}, {}", magicNum, version, serializerType, messageType, sequenceId, length);
        log.debug("{}", message);
        out.add(message);

    }
}

测试

package cn.itcast.protocol;

import cn.itcast.message.LoginRequestMessage;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.logging.LoggingHandler;

public class TestMessageCodec {
    public static void main(String[] args) throws Exception {
        EmbeddedChannel channel = new EmbeddedChannel(
                // 4 + 1 + 1 + 1 + 4 + 1 = 12
                new LengthFieldBasedFrameDecoder(1024, 12, 4, 0, 0),  // 解决黏包/半包问题
                new LoggingHandler(),
                new MessageCodec());

        // 编码 encode
        LoginRequestMessage message = new LoginRequestMessage("zhangsan", "123", "张三");
        channel.writeOutbound(message);

        // 解码 decode
        ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
        new MessageCodec().encode(null, message, buf);
        // 入站
        channel.writeInbound(buf);
    }
}

输出

10:48:30 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] REGISTERED
10:48:30 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] ACTIVE
10:48:30 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] WRITE: 239B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 01 02 03 04 01 00 00 00 00 00 00 ff 00 00 00 df |................|
|00000010| ac ed 00 05 73 72 00 25 63 6e 2e 69 74 63 61 73 |....sr.%cn.itcas|
|00000020| 74 2e 6d 65 73 73 61 67 65 2e 4c 6f 67 69 6e 52 |t.message.LoginR|
|00000030| 65 71 75 65 73 74 4d 65 73 73 61 67 65 69 16 46 |equestMessagei.F|
|00000040| e8 ec d3 7b b7 02 00 03 4c 00 08 6e 69 63 6b 6e |...{....L..nickn|
|00000050| 61 6d 65 74 00 12 4c 6a 61 76 61 2f 6c 61 6e 67 |amet..Ljava/lang|
|00000060| 2f 53 74 72 69 6e 67 3b 4c 00 08 70 61 73 73 77 |/String;L..passw|
|00000070| 6f 72 64 71 00 7e 00 01 4c 00 08 75 73 65 72 6e |ordq.~..L..usern|
|00000080| 61 6d 65 71 00 7e 00 01 78 72 00 19 63 6e 2e 69 |ameq.~..xr..cn.i|
|00000090| 74 63 61 73 74 2e 6d 65 73 73 61 67 65 2e 4d 65 |tcast.message.Me|
|000000a0| 73 73 61 67 65 f7 65 86 73 f4 a4 ab 03 02 00 02 |ssage.e.s.......|
|000000b0| 49 00 0b 6d 65 73 73 61 67 65 54 79 70 65 49 00 |I..messageTypeI.|
|000000c0| 0a 73 65 71 75 65 6e 63 65 49 64 78 70 00 00 00 |.sequenceIdxp...|
|000000d0| 00 00 00 00 00 74 00 06 e5 bc a0 e4 b8 89 74 00 |.....t........t.|
|000000e0| 03 31 32 33 74 00 08 7a 68 61 6e 67 73 61 6e |.123t..zhangsan |
+--------+-------------------------------------------------+----------------+
10:48:30 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] FLUSH
10:48:30 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] READ: 239B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 01 02 03 04 01 00 00 00 00 00 00 ff 00 00 00 df |................|
|00000010| ac ed 00 05 73 72 00 25 63 6e 2e 69 74 63 61 73 |....sr.%cn.itcas|
|00000020| 74 2e 6d 65 73 73 61 67 65 2e 4c 6f 67 69 6e 52 |t.message.LoginR|
|00000030| 65 71 75 65 73 74 4d 65 73 73 61 67 65 69 16 46 |equestMessagei.F|
|00000040| e8 ec d3 7b b7 02 00 03 4c 00 08 6e 69 63 6b 6e |...{....L..nickn|
|00000050| 61 6d 65 74 00 12 4c 6a 61 76 61 2f 6c 61 6e 67 |amet..Ljava/lang|
|00000060| 2f 53 74 72 69 6e 67 3b 4c 00 08 70 61 73 73 77 |/String;L..passw|
|00000070| 6f 72 64 71 00 7e 00 01 4c 00 08 75 73 65 72 6e |ordq.~..L..usern|
|00000080| 61 6d 65 71 00 7e 00 01 78 72 00 19 63 6e 2e 69 |ameq.~..xr..cn.i|
|00000090| 74 63 61 73 74 2e 6d 65 73 73 61 67 65 2e 4d 65 |tcast.message.Me|
|000000a0| 73 73 61 67 65 f7 65 86 73 f4 a4 ab 03 02 00 02 |ssage.e.s.......|
|000000b0| 49 00 0b 6d 65 73 73 61 67 65 54 79 70 65 49 00 |I..messageTypeI.|
|000000c0| 0a 73 65 71 75 65 6e 63 65 49 64 78 70 00 00 00 |.sequenceIdxp...|
|000000d0| 00 00 00 00 00 74 00 06 e5 bc a0 e4 b8 89 74 00 |.....t........t.|
|000000e0| 03 31 32 33 74 00 08 7a 68 61 6e 67 73 61 6e |.123t..zhangsan |
+--------+-------------------------------------------------+----------------+
10:48:31 [DEBUG] [main] c.i.p.MessageCodec - 16909060, 1, 0, 0, 0, 223
10:48:31 [DEBUG] [main] c.i.p.MessageCodec - LoginRequestMessage(super=Message(sequenceId=0, messageType=0), username=zhangsan, password=123, nickname=张三)
10:48:31 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] READ COMPLETE

或：验证LengthFieldBasedFrameDecoder帧解码器对黏包/半包的影响

EmbeddedChannel channel = new EmbeddedChannel(
    new LengthFieldBasedFrameDecoder(1024, 12, 4, 0, 0),
    new LoggingHandler(),
    new MessageCodec()
);
// encode
LoginRequestMessage message = new LoginRequestMessage("zhangsan", "123", "张三");
//        channel.writeOutbound(message);

// decode
ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
new MessageCodec().encode(null, message, buf);

ByteBuf s1 = buf.slice(0, 100);
ByteBuf s2 = buf.slice(100, buf.readableBytes() - 100);
s1.retain(); // 引用计数 2
channel.writeInbound(s1); // release 1
channel.writeInbound(s2);

💡什么时候可以加 @Sharable

当handler不保存状态时，就可以安全地在多线程下被共享
但要注意对于编解码器类，不能继承ByteToMessageCodec 或 CombinedChannelDuplexHandler 父类，他们的构造方法对@Sharable有限制
如果能确保编解码器不会保存状态，可以继承MessageToMessageCodec父类

不可共享：

package cn.itcast.protocol;

import cn.itcast.message.LoginRequestMessage;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.logging.LoggingHandler;

public class TestMessageCodec {
    public static void main(String[] args) throws Exception {

        // 工人1  1234
//                        - 把工人1的一部分数据和工人2的一部分数据拼接成完整的数据（多次记录了消息之间的状态，线程不安全，不能在多线程下共享）
        // 工人2  1234
        LengthFieldBasedFrameDecoder FRAME_DECODER = new LengthFieldBasedFrameDecoder(1024, 12, 4, 0, 0);// 解决黏包/半包问题

        // 不会保存上一次的状态信息（线程安全）
        LoggingHandler LOGGING_HANDLER = new LoggingHandler();

        EmbeddedChannel channel = new EmbeddedChannel(
                LOGGING_HANDLER,
                FRAME_DECODER,
                new MessageCodec());

        // 编码 encode
        LoginRequestMessage message = new LoginRequestMessage("zhangsan", "123", "张三");
        channel.writeOutbound(message);

        // 解码 decode
        ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
        new MessageCodec().encode(null, message, buf);
        // 入站
        channel.writeInbound(buf);
    }
}

可共享：MessageToMessageCodec（不涉及ByteBuf的内部状态管理）

package cn.itcast.protocol;

import cn.itcast.message.Message;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageCodec;
import lombok.extern.slf4j.Slf4j;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.List;

@Slf4j
@ChannelHandler.Sharable
/**
 * 必须和 LengthFieldBasedFrameDecoder 一起使用，确保接到的 ByteBuf 消息是完整的
 */
public class MessageCodecSharable extends MessageToMessageCodec<ByteBuf, Message> {
    @Override
    protected void encode(ChannelHandlerContext ctx, Message msg, List<Object> outList) throws Exception {
        ByteBuf out = ctx.alloc().buffer();
        // 1. 4 字节的魔数
        out.writeBytes(new byte[]{1, 2, 3, 4});
        // 2. 1 字节的版本,
        out.writeByte(1);
        // 3. 1 字节的序列化方式 jdk 0 , json 1
        out.writeByte(0);
        // 4. 1 字节的指令类型
        out.writeByte(msg.getMessageType());
        // 5. 4 个字节
        out.writeInt(msg.getSequenceId());
        // 无意义，对齐填充
        out.writeByte(0xff);
        // 6. 获取内容的字节数组
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(msg);
        byte[] bytes = bos.toByteArray();
        // 7. 长度
        out.writeInt(bytes.length);
        // 8. 写入内容
        out.writeBytes(bytes);
        outList.add(out);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        int magicNum = in.readInt();
        byte version = in.readByte();
        byte serializerType = in.readByte();
        byte messageType = in.readByte();
        int sequenceId = in.readInt();
        in.readByte();
        int length = in.readInt();
        byte[] bytes = new byte[length];
        in.readBytes(bytes, 0, length);
        ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bytes));
        Message message = (Message) ois.readObject();
        log.debug("{}, {}, {}, {}, {}, {}", magicNum, version, serializerType, messageType, sequenceId, length);
        log.debug("{}", message);
        out.add(message);
    }
}

3. 聊天室案例

3.1 聊天室业务介绍

（1）用户管理

/**
 * 用户管理接口
 */
public interface UserService {

    /**
     * 登录
     * @param username 用户名
     * @param password 密码
     * @return 登录成功返回 true, 否则返回 false
     */
    boolean login(String username, String password);
}

（2）会话管理

/**
 * 会话管理接口
 */
public interface Session {

    /**
     * 绑定会话
     * @param channel 哪个 channel 要绑定会话
     * @param username 会话绑定用户
     */
    void bind(Channel channel, String username);

    /**
     * 解绑会话
     * @param channel 哪个 channel 要解绑会话
     */
    void unbind(Channel channel);

    /**
     * 获取属性
     * @param channel 哪个 channel
     * @param name 属性名
     * @return 属性值
     */
    Object getAttribute(Channel channel, String name);

    /**
     * 设置属性
     * @param channel 哪个 channel
     * @param name 属性名
     * @param value 属性值
     */
    void setAttribute(Channel channel, String name, Object value);

    /**
     * 根据用户名获取 channel
     * @param username 用户名
     * @return channel
     */
    Channel getChannel(String username);
}

（3）聊天组会话管理

/**
 * 聊天组会话管理接口
 */
public interface GroupSession {

    /**
     * 创建一个聊天组, 如果不存在才能创建成功, 否则返回 null
     * @param name 组名
     * @param members 成员
     * @return 成功时返回组对象, 失败返回 null
     */
    Group createGroup(String name, Set<String> members);

    /**
     * 加入聊天组
     * @param name 组名
     * @param member 成员名
     * @return 如果组不存在返回 null, 否则返回组对象
     */
    Group joinMember(String name, String member);

    /**
     * 移除组成员
     * @param name 组名
     * @param member 成员名
     * @return 如果组不存在返回 null, 否则返回组对象
     */
    Group removeMember(String name, String member);

    /**
     * 移除聊天组
     * @param name 组名
     * @return 如果组不存在返回 null, 否则返回组对象
     */
    Group removeGroup(String name);

    /**
     * 获取组成员
     * @param name 组名
     * @return 成员集合, 没有成员会返回 empty set
     */
    Set<String> getMembers(String name);

    /**
     * 获取组成员的 channel 集合, 只有在线的 channel 才会返回
     * @param name 组名
     * @return 成员 channel 集合
     */
    List<Channel> getMembersChannel(String name);
}

3.2 聊天室业务 - 登录

步骤①：修改LoginRequestMessage的有参构造，去掉nickname参数

    public LoginRequestMessage(String username, String password) {
        this.username = username;
        this.password = password;
    }

②LoginResponseMessage中覆盖父类的构造方法

    public LoginResponseMessage(boolean success, String reason) {
        super(success, reason);
    }

③修改ChatServer，添加handler

package cn.itcast.server;

import cn.itcast.message.LoginRequestMessage;
import cn.itcast.message.LoginResponseMessage;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import cn.itcast.server.service.UserServiceFactory;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
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.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class ChatServer {
    public static void main(String[] args) {
        NioEventLoopGroup boss = new NioEventLoopGroup();
        NioEventLoopGroup worker = new NioEventLoopGroup();
        LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
        MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.group(boss, worker);
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC);
                    ch.pipeline().addLast(new SimpleChannelInboundHandler<LoginRequestMessage>() {
                        @Override
                        protected void channelRead0(ChannelHandlerContext ctx, LoginRequestMessage msg) throws Exception {
                            String username = msg.getUsername();
                            String password = msg.getPassword();
                            boolean login = UserServiceFactory.getUserService().login(username, password);
                            LoginResponseMessage responseMessage;
                            if (login) {
                                responseMessage = new LoginResponseMessage(true, "登录成功");
                            } else {
                                responseMessage = new LoginResponseMessage(false, "用户名或密码错误");
                            }
                            ctx.writeAndFlush(responseMessage);
                        }
                    });
                }
            });

            Channel channel = serverBootstrap.bind(8080).sync().channel();
            channel.closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }
}

④修改ChatClient，添加handler

package cn.itcast.client;

import cn.itcast.message.LoginRequestMessage;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.util.Scanner;

@Slf4j
public class ChatClient {
    public static void main(String[] args) {
        NioEventLoopGroup group = new NioEventLoopGroup();
        LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
        MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();

        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(group);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC);
                    ch.pipeline().addLast("client_handler", new ChannelInboundHandlerAdapter() {
                        // 在连接建立后触发active事件
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            // 接收用户在控制台的输入，向服务器发送各种消息
                            new Thread(() -> {
                                Scanner sc = new Scanner(System.in);
                                System.out.println("请输入用户名:");
                                String username = sc.nextLine();
                                System.out.println("请输入密码:");
                                String password = sc.nextLine();
                                // 构造消息对象
                                LoginRequestMessage message = new LoginRequestMessage(username, password);
                                // 发送消息
                                ctx.writeAndFlush(message);

                                System.out.println("等待后续操作...");
                                try {
                                    System.in.read();
                                } catch (IOException e) {
                                    throw new RuntimeException(e);
                                }
                            }, "system in").start();
                        }

                        @Override
                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                            log.debug("msg: {}", msg);
                        }
                    });
                }
            });

            Channel channel = bootstrap.connect("localhost", 8080).sync().channel();
            channel.closeFuture().sync();
        } catch (Exception e) {
            log.error("client error", e);
        } finally {
            group.shutdownGracefully();
        }
    }
}

⑤测试

ChatClient输出：

请输入用户名:
zhangsan
请输入密码:
123
等待后续操作...
14:39:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6d2940ad, L:/127.0.0.1:50225 - R:localhost/127.0.0.1:8080] WRITE: 231B
// 。。。省略。。。
14:39:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6d2940ad, L:/127.0.0.1:50225 - R:localhost/127.0.0.1:8080] FLUSH
14:39:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6d2940ad, L:/127.0.0.1:50225 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
14:39:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
14:39:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))

ChatServer输出：

14:39:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd32608ca, L:/127.0.0.1:8080 - R:/127.0.0.1:50225] READ: 231B
// 。。。省略。。。
14:39:00 [DEBUG] [nioEventLoopGroup-3-1] c.i.p.MessageCodecSharable - LoginRequestMessage(super=Message(sequenceId=0, messageType=0), username=zhangsan, password=123, nickname=null)
14:39:00 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0xd32608ca, L:/127.0.0.1:8080 - R:/127.0.0.1:50225] WRITE: 262B
// 。。。省略。。。

⑥改进客户端代码（提供菜单）

package cn.itcast.client;

import cn.itcast.message.*;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.util.*;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;

@Slf4j
public class ChatClient {
    public static void main(String[] args) {
        NioEventLoopGroup group = new NioEventLoopGroup();
        LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
        MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();

        CountDownLatch WAIT_FOR_LOGIN = new CountDownLatch(1);
        AtomicBoolean LOGIN = new AtomicBoolean(false);
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(group);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC);
                    ch.pipeline().addLast("client_handler", new ChannelInboundHandlerAdapter() {
                        // 在连接建立后触发active事件
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception {
                            // 接收用户在控制台的输入，向服务器发送各种消息
                            new Thread(() -> {
                                Scanner sc = new Scanner(System.in);
                                System.out.println("请输入用户名:");
                                String username = sc.nextLine();
                                System.out.println("请输入密码:");
                                String password = sc.nextLine();
                                // 构造消息对象
                                LoginRequestMessage message = new LoginRequestMessage(username, password);
                                // 发送消息
                                ctx.writeAndFlush(message);

                                try {
                                    WAIT_FOR_LOGIN.await();
                                } catch (InterruptedException e) {
                                    throw new RuntimeException(e);
                                }
                                if (!LOGIN.get()) {
                                    // 登录失败
                                    ctx.close();
                                    return;
                                }
                                while (true) {
                                    // 输出菜单
                                    System.out.println("==================================");
                                    System.out.println("send [username] [content]");
                                    System.out.println("gsend [group name] [content]");
                                    System.out.println("gcreate [group name] [m1,m2,m3...]");
                                    System.out.println("gmembers [group name]");
                                    System.out.println("gjoin [group name]");
                                    System.out.println("gquit [group name]");
                                    System.out.println("quit");
                                    System.out.println("==================================");

                                    String command = sc.nextLine();
                                    String[] s = command.split(" ");
                                    switch (s[0]) {
                                        case "send":
                                            ctx.writeAndFlush(new ChatRequestMessage(username, s[1], s[2]));
                                            break;
                                        case "gsend":
                                            ctx.writeAndFlush(new GroupChatRequestMessage(username, s[1], s[2]));
                                            break;
                                        case "gcreate":
                                            Set<String> set = new HashSet<>(Arrays.asList(s[2].split(",")));
                                            set.add(username);  // 加入自己
                                            ctx.writeAndFlush(new GroupCreateRequestMessage(s[1], set));
                                            break;
                                        case "gmembers":
                                            ctx.writeAndFlush(new GroupMembersRequestMessage(s[1]));
                                            break;
                                        case "gjoin":
                                            ctx.writeAndFlush(new GroupJoinRequestMessage(username, s[1]));
                                            break;
                                        case "gquit":
                                            ctx.writeAndFlush(new GroupQuitRequestMessage(username, s[1]));
                                            break;
                                        case "quit":
                                            ctx.channel().close();
                                            break;
                                    }
                                }
                            }, "system in").start();
                        }

                        @Override
                        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                            log.debug("msg: {}", msg);
                            if (msg instanceof LoginResponseMessage) {
                                // 登录响应
                                LoginResponseMessage response = (LoginResponseMessage) msg;
                                if (response.isSuccess()) {
                                    // 登录成功
                                    LOGIN.set(true);
                                }
                                // 响应回来的时候减一，唤醒“system in”线程
                                WAIT_FOR_LOGIN.countDown();
                            }
                        }
                    });
                }
            });

            Channel channel = bootstrap.connect("localhost", 8080).sync().channel();
            channel.closeFuture().sync();
        } catch (Exception e) {
            log.error("client error", e);
        } finally {
            group.shutdownGracefully();
        }
    }
}

3.3 聊天室业务 - 单聊

①修改服务端代码

选中 SimpleChannelInboundHandler，右键选择Refactor，点击 Convert Anonymous to Inner，重构 LoginRequestMessageHandler

移动类到外部

加上 @ChannelHandler.Sharable 注解，效果如下：

package cn.itcast.handler;

import cn.itcast.message.LoginRequestMessage;
import cn.itcast.message.LoginResponseMessage;
import cn.itcast.server.service.UserServiceFactory;
import cn.itcast.server.session.SessionFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

@ChannelHandler.Sharable
public class LoginRequestMessageHandler extends SimpleChannelInboundHandler<LoginRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoginRequestMessage msg) throws Exception {
        String username = msg.getUsername();
        String password = msg.getPassword();
        boolean login = UserServiceFactory.getUserService().login(username, password);
        LoginResponseMessage responseMessage;
        if (login) {
            responseMessage = new LoginResponseMessage(true, "登录成功");
            // 保存用户会话
            SessionFactory.getSession().bind(ctx.channel(), username);
        } else {
            responseMessage = new LoginResponseMessage(false, "用户名或密码错误");
        }
        ctx.writeAndFlush(responseMessage);
    }
}

②添加ChatRequestMessageHandler

package cn.itcast.handler;

import cn.itcast.message.ChatRequestMessage;
import cn.itcast.message.ChatResponseMessage;
import cn.itcast.server.session.SessionFactory;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

@ChannelHandler.Sharable
public class ChatRequestMessageHandler extends SimpleChannelInboundHandler<ChatRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ChatRequestMessage msg) throws Exception {
        String to = msg.getTo();
        // 找到对方的channel
        Channel channel = SessionFactory.getSession().getChannel(to);
        // 在线
        if (channel != null) {
            channel.writeAndFlush(new ChatResponseMessage(msg.getFrom(), msg.getContent()));
        }
        // 不在线
        else {
            ctx.writeAndFlush(new ChatResponseMessage(false, "对方用户不在线或不存在"));
        }
    }
}

③修改ChatService，添加ChatRequestMessageHandler

package cn.itcast.server;

import cn.itcast.handler.ChatRequestMessageHandler;
import cn.itcast.handler.LoginRequestMessageHandler;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
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 lombok.extern.slf4j.Slf4j;

@Slf4j
public class ChatServer {
    public static void main(String[] args) {
        NioEventLoopGroup boss = new NioEventLoopGroup();
        NioEventLoopGroup worker = new NioEventLoopGroup();
        LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
        MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();
        LoginRequestMessageHandler LOGIN_HANDLER = new LoginRequestMessageHandler();
        ChatRequestMessageHandler CHAT_HANDLER = new ChatRequestMessageHandler();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.group(boss, worker);
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC);
                    ch.pipeline().addLast(LOGIN_HANDLER);
                    ch.pipeline().addLast(CHAT_HANDLER);
                }
            });

            Channel channel = serverBootstrap.bind(8080).sync().channel();
            channel.closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }

}

④启用一个server，两个client进行测试

client1 输出：

请输入用户名:
lisi
请输入密码:
123
15:48:15 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xa91f330e, L:/127.0.0.1:52178 - R:localhost/127.0.0.1:8080] WRITE: 227B
// 。。。省略。。。
15:48:15 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
15:48:15 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xa91f330e, L:/127.0.0.1:52178 - R:localhost/127.0.0.1:8080] READ COMPLETE
==================================
send [username] [content]
gsend [group name] [content]
gcreate [group name] [m1,m2,m3...]
gmembers [group name]
gjoin [group name]
gquit [group name]
quit
==================================
send zhangsan 你好，张三，我是李四
==================================
15:48:59 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xa91f330e, L:/127.0.0.1:52178 - R:localhost/127.0.0.1:8080] WRITE: 252B
// 。。。省略。。。
15:48:59 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xa91f330e, L:/127.0.0.1:52178 - R:localhost/127.0.0.1:8080] FLUSH
15:49:51 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xa91f330e, L:/127.0.0.1:52178 - R:localhost/127.0.0.1:8080] READ: 303B
// 。。。省略。。。
15:49:51 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: ChatResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=3), success=false, reason=null), from=zhangsan, content=你好，李四)

client 2输出：

请输入用户名:
zhangsan
请输入密码:
123
15:48:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] WRITE: 231B
// 。。。省略。。。
15:48:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] FLUSH
15:48:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
15:48:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
15:48:59 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] READ: 314B
// 。。。省略。。。
15:48:59 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: ChatResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=3), success=false, reason=null), from=lisi, content=你好，张三，我是李四)
15:48:59 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] READ COMPLETE
send lisi 你好，李四
==================================
send [username] [content]
gsend [group name] [content]
gcreate [group name] [m1,m2,m3...]
gmembers [group name]
gjoin [group name]
gquit [group name]
quit
==================================
15:49:51 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x909b38c1, L:/127.0.0.1:52272 - R:localhost/127.0.0.1:8080] WRITE: 237B
// 。。。省略。。。

3.4 聊天室业务 - 群聊

（1）创建群聊

①新建GroupCreateRequestMessageHandler

package cn.itcast.handler;

import cn.itcast.message.GroupCreateRequestMessage;
import cn.itcast.message.GroupCreateResponseMessage;
import cn.itcast.server.session.Group;
import cn.itcast.server.session.GroupSession;
import cn.itcast.server.session.GroupSessionFactory;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.util.List;
import java.util.Set;

@ChannelHandler.Sharable
public class GroupCreateRequestMessageHandler extends SimpleChannelInboundHandler<GroupCreateRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, GroupCreateRequestMessage msg) throws Exception {
        String groupName = msg.getGroupName();
        Set<String> members = msg.getMembers();
        // 群管理器
        GroupSession groupSession = GroupSessionFactory.getGroupSession();
        Group group = groupSession.createGroup(groupName, members);
        if (group == null) {
            // 发送成功消息
            ctx.writeAndFlush(new GroupCreateResponseMessage(true, groupName + "创建成功"));
            // 发送拉取消息
            List<Channel> channels = groupSession.getMembersChannel(groupName);
            for (Channel channel : channels) {
                channel.writeAndFlush(new GroupCreateResponseMessage(true, "您已被拉入" + groupName));
            }
        } else {
            ctx.writeAndFlush(new GroupCreateResponseMessage(false, groupName + "群聊已经存在"));
        }
    }
}

②在服务器ChatServer添加handler

package cn.itcast.server;

import cn.itcast.handler.*;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
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 lombok.extern.slf4j.Slf4j;

@Slf4j
public class ChatServer {
    public static void main(String[] args) {
        // ... ...
        ChatRequestMessageHandler CHAT_HANDLER = new ChatRequestMessageHandler();
        GroupCreateRequestMessageHandler GROUP_CREATE_HANDLER = new GroupCreateRequestMessageHandler();

        try {
            // ... ...
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    // ... ...
                    ch.pipeline().addLast(CHAT_HANDLER);
                    ch.pipeline().addLast(GROUP_CREATE_HANDLER);
                }
            });

            // ... ...
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }

}

③启动一个ChatServer、三个ChatClient进行测试

Client 1输出

请输入用户名:
zhangsan
请输入密码:
123
16:24:38 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3ed2514d, L:/127.0.0.1:53651 - R:localhost/127.0.0.1:8080] WRITE: 231B
// 。。。省略。。。
16:24:38 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
==================================
gcreate 群聊1 lisi,wangwu
==================================
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3ed2514d, L:/127.0.0.1:53651 - R:localhost/127.0.0.1:8080] WRITE: 291B
// 。。。省略。。。
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3ed2514d, L:/127.0.0.1:53651 - R:localhost/127.0.0.1:8080] READ: 275B
// 。。。省略。。。
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=群聊1创建成功))
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3ed2514d, L:/127.0.0.1:53651 - R:localhost/127.0.0.1:8080] READ COMPLETE
16:25:38 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x41247eac, L:/127.0.0.1:61573 - R:localhost/127.0.0.1:8080] READ: 278B
// 。。。省略。。。
1625:38 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))

Client 2输出

请输入用户名:
lisi
请输入密码:
123
16:24:43 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x4deb8f20, L:/127.0.0.1:53725 - R:localhost/127.0.0.1:8080] WRITE: 227B
// 。。。省略。。。
16:24:43 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x4deb8f20, L:/127.0.0.1:53725 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
16:24:43 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x4deb8f20, L:/127.0.0.1:53725 - R:localhost/127.0.0.1:8080] READ: 278B
// 。。。省略。。。
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))

Client 3输出

请输入用户名:
wangwu
请输入密码:
123
16:24:48 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x42c3956d, L:/127.0.0.1:53798 - R:localhost/127.0.0.1:8080] WRITE: 229B
// 。。。省略。。。
16:24:48 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x42c3956d, L:/127.0.0.1:53798 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
16:24:48 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x42c3956d, L:/127.0.0.1:53798 - R:localhost/127.0.0.1:8080] READ: 278B
// 。。。省略。。。
16:25:37 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))

（2）发送群聊消息

①添加GroupChatRequestMessageHandler

package cn.itcast.handler;

import cn.itcast.message.GroupChatRequestMessage;
import cn.itcast.message.GroupChatResponseMessage;
import cn.itcast.server.session.GroupSessionFactory;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.util.List;

@ChannelHandler.Sharable
public class GroupChatRequestMessageHandler extends SimpleChannelInboundHandler<GroupChatRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, GroupChatRequestMessage msg) throws Exception {
        List<Channel> channels = GroupSessionFactory.getGroupSession()
                .getMembersChannel(msg.getGroupName());

        for (Channel channel : channels) {
            channel.writeAndFlush(new GroupChatResponseMessage(msg.getFrom(), msg.getContent()));
        }
    }
}

②添加handler

package cn.itcast.server;

import cn.itcast.handler.*;
import cn.itcast.protocol.MessageCodecSharable;
import cn.itcast.protocol.ProcotolFrameDecoder;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
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 lombok.extern.slf4j.Slf4j;

@Slf4j
public class ChatServer {
    public static void main(String[] args) {
        // ... ...
        GroupCreateRequestMessageHandler GROUP_CREATE_HANDLER = new GroupCreateRequestMessageHandler();
        GroupJoinRequestMessageHandler GROUP_JOIN_HANDLER = new GroupJoinRequestMessageHandler();
        GroupMembersRequestMessageHandler GROUP_MEMBERS_HANDLER = new GroupMembersRequestMessageHandler();
        GroupQuitRequestMessageHandler GROUP_QUIT_HANDLER = new GroupQuitRequestMessageHandler();
        GroupChatRequestMessageHandler GROUP_CHAT_HANDLER = new GroupChatRequestMessageHandler();
        QuitHandler QUIT_HANDLER = new QuitHandler();

        try {
            // ... ...
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    // ... ...
                    ch.pipeline().addLast(GROUP_CREATE_HANDLER);
                    ch.pipeline().addLast(GROUP_JOIN_HANDLER);
                    ch.pipeline().addLast(GROUP_MEMBERS_HANDLER);
                    ch.pipeline().addLast(GROUP_QUIT_HANDLER);
                    ch.pipeline().addLast(GROUP_CHAT_HANDLER);
                    ch.pipeline().addLast(QUIT_HANDLER);
                }
            });

            // ... ...
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }

}

③测试

client 1输出

请输入用户名:
zhangsan
请输入密码:
123
16:48:39 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] WRITE: 231B
// 。。。省略。。。
16:48:39 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
16:48:39 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
16:48:39 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ COMPLETE
gcreate 群聊1 lisi,wangwu
==================================
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] WRITE: 302B
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ: 275B
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=群聊1创建成功))
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ COMPLETE
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ: 278B
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ COMPLETE
gsend 群聊1 大家好，我是张三
==================================
// 。。。省略。。。
16:49:54 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] WRITE: 261B
// 。。。省略。。。
16:49:54 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x96065683, L:/127.0.0.1:49946 - R:localhost/127.0.0.1:8080] READ: 317B
// 。。。省略。。。
16:49:54 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupChatResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=11), success=false, reason=null), from=zhangsan, content=大家好，我是张三)

client 2 和 client 3输出类似

请输入用户名:
lisi
请输入密码:
123
16:48:46 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] WRITE: 227B
// 。。。省略。。。
16:48:46 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] READ: 262B
// 。。。省略。。。
16:48:46 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
==================================
16:48:46 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] READ COMPLETE
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] READ: 278B
// 。。。省略。。。
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊1))
16:49:23 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] READ COMPLETE
16:49:54 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x6583f474, L:/127.0.0.1:50148 - R:localhost/127.0.0.1:8080] READ: 317B
// 。。。省略。。。
16:49:54 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupChatResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=11), success=false, reason=null), from=zhangsan, content=大家好，我是张三)

（3）加入群聊

①添加GroupJoinRequestMessageHandler

package cn.itcast.handler;

import cn.itcast.message.GroupJoinRequestMessage;
import cn.itcast.message.GroupJoinResponseMessage;
import cn.itcast.server.session.Group;
import cn.itcast.server.session.GroupSessionFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

@ChannelHandler.Sharable
public class GroupJoinRequestMessageHandler extends SimpleChannelInboundHandler<GroupJoinRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, GroupJoinRequestMessage msg) throws Exception {
        Group group = GroupSessionFactory.getGroupSession().joinMember(msg.getGroupName(), msg.getUsername());
        if (group != null) {
            ctx.writeAndFlush(new GroupJoinResponseMessage(true, msg.getGroupName() + "群聊加入成功"));
        } else {
            ctx.writeAndFlush(new GroupJoinResponseMessage(false, msg.getGroupName() + "群聊不存在"));
        }
    }
}

②启动一个服务端，四个客户端进行测试

client 1输出

请输入用户名:
zhangsan
请输入密码:
123
20:42:10 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
==================================
gcreate 群聊2 lisi,wangwu
==================================
20:42:46 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=群聊2创建成功))
// 。。。省略。。。
20:42:46 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊2))

client 2 输出

请输入用户名:
lisi
请输入密码:
123
20:42:15 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
20:42:46 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊2))

client 3输出

请输入用户名:
wangwu
请输入密码:
123
20:42:21 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
20:42:46 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupCreateResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=5), success=true, reason=您已被拉入群聊2))

client 4输出

请输入用户名:
zhaoliu
请输入密码:
123
20:43:02 [DEBUG] [nioEventLoopGroup-2-1] c.i.p.MessageCodecSharable - LoginResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=1), success=true, reason=登录成功))
// 。。。省略。。。
==================================
gjoin 群聊2
==================================
// 。。。省略。。。
20:43:14 [DEBUG] [nioEventLoopGroup-2-1] c.i.c.ChatClient - msg: GroupJoinResponseMessage(super=AbstractResponseMessage(super=Message(sequenceId=0, messageType=7), success=true, reason=群聊2群聊加入成功)

（4）退出群聊

package cn.itcast.handler;

import cn.itcast.message.GroupJoinResponseMessage;
import cn.itcast.message.GroupQuitRequestMessage;
import cn.itcast.server.session.Group;
import cn.itcast.server.session.GroupSessionFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

@ChannelHandler.Sharable
public class GroupQuitRequestMessageHandler extends SimpleChannelInboundHandler<GroupQuitRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, GroupQuitRequestMessage msg) throws Exception {
        Group group = GroupSessionFactory.getGroupSession().removeMember(msg.getGroupName(), msg.getUsername());
        
        if (group != null) {
            ctx.writeAndFlush(new GroupJoinResponseMessage(true, "已退出群" + msg.getGroupName()));
        } else {
            ctx.writeAndFlush(new GroupJoinResponseMessage(true, msg.getGroupName() + "群不存在"));
        }
    }
}

（5）查看群聊成员

package cn.itcast.handler;

import cn.itcast.message.GroupMembersRequestMessage;
import cn.itcast.message.GroupMembersResponseMessage;
import cn.itcast.server.session.GroupSessionFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.util.Set;

@ChannelHandler.Sharable
public class GroupMembersRequestMessageHandler extends SimpleChannelInboundHandler<GroupMembersRequestMessage> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, GroupMembersRequestMessage msg) throws Exception {
        Set<String> members = GroupSessionFactory.getGroupSession().getMembers(msg.getGroupName());
        ctx.writeAndFlush(new GroupMembersResponseMessage(members));
    }
}

3.5 聊天室业务 - 退出

①添加QuitHandler


package cn.itcast.handler;

import cn.itcast.server.session.SessionFactory;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import lombok.extern.slf4j.Slf4j;

@Slf4j
@ChannelHandler.Sharable
public class QuitHandler extends ChannelInboundHandlerAdapter {

    /**
     * 当连接断开时触发inactive事件
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        SessionFactory.getSession().unbind(ctx.channel());
        log.debug("{} 已经断开", ctx.channel());
    }

    /**
     * 客户端直接关闭时触发
     * @param ctx
     * @param cause
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        SessionFactory.getSession().unbind(ctx.channel());
        log.debug("{} 已经异常断开, 异常是{}", ctx.channel(), cause.getMessage());
    }
}

3.6 聊天室业务 - 空闲检测

连接假死

原因

网络设备出现故障，例如网卡、机房等，底层的TCP连接已经断开了，但应用程序没有感知到，仍然占用着资源；
公网网络不稳定，出现丢包。如果连续出现丢包，这时现象就是客户端数据发不出去，服务端也一直收不到数据，就这么一直耗着；
应用程序线程阻塞，无法进行数据读写

问题

假死的连接占用的资源不能自动释放；
向假死的连接发送数据，得到的反馈是发送超时

服务器端解决

怎么判断客户端连接是否假死呢？如果能收到客户端数据，说明没有假死。因此策略就可以定为，每隔一段时间就检查这段时间内是否接收到客户端数据，没有就可以判断为连接假死。

package cn.itcast.server;

// ... ...
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class ChatServer {
    public static void main(String[] args) {
        // ... ...

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.group(boss, worker);
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC);
                    // 用来判断是不是读空闲时间过长，或者写空闲时间过长
                    // 如果5秒内没有接收到channel的数据，会触发一个 IdleState#READER_IDLE 事件
                    ch.pipeline().addLast(new IdleStateHandler(5, 0, 0));
                    // ChannelDuplexHandler可以同时作为入站和出站处理器
                    ch.pipeline().addLast(new ChannelDuplexHandler() {
                        // 用来触发特殊事件
                        @Override
                        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
                            IdleStateEvent event = (IdleStateEvent) evt;
                            // 触发了读空闲事件
                            if (event.state() == IdleState.READER_IDLE) {
                                log.debug("读空闲已经超过5秒");
                                // 关闭channel
                                ctx.channel().close();
                            }
                            super.userEventTriggered(ctx, evt);
                        }
                    });
                    // ... ...
                }
            });

            Channel channel = serverBootstrap.bind(8080).sync().channel();
            channel.closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("server error", e);
        } finally {
            boss.shutdownGracefully();
            worker.shutdownGracefully();
        }
    }

}

客户端定时心跳

客户端可以定时向服务器端发送数据，只要这个时间间隔小于服务器定义的空闲检测的时间间隔，那么就能防止前面提到的误判，客户端可以定义如下心跳处理器

①在Message中添加如下

    public static final  int PingMessage = 14;
    public static final int PongMessage = 15;

②添加PingMessage

package cn.itcast.message;

public class PingMessage extends Message{
    @Override
    public int getMessageType() {
        return PingMessage;
    }
}

③修改ChatClient

package cn.itcast.client;

// ... ...

@Slf4j
public class ChatClient {
    public static void main(String[] args) {
        // ... ... 
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(group);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new ProcotolFrameDecoder());
//                    ch.pipeline().addLast(LOGGING_HANDLER);
                    ch.pipeline().addLast(MESSAGE_CODEC); 

                    // 用来判断是不是读空闲时间过长，或者写空闲时间过长
                    // 3s内如果没有向服务器写数据，会触发一个 IdleState#WRITER_IDLE 事件
                    ch.pipeline().addLast(new IdleStateHandler(0, 3, 0));
                    ch.pipeline().addLast(new ChannelDuplexHandler() {
                        // 用来触发特殊事件
                        @Override
                        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
                            IdleStateEvent event = (IdleStateEvent) evt;
                            // 触发了读空闲事件
                            if (event.state() == IdleState.WRITER_IDLE) {
                                log.debug("写空闲已经超过3秒，发送一个心跳包");
                                ctx.writeAndFlush(new PingMessage());
                            }
                            super.userEventTriggered(ctx, evt);
                        }
                    });
                    // ... ...
        } catch (Exception e) {
            log.error("client error", e);
        } finally {
            group.shutdownGracefully();
        }
    }
}