三. Netty 进阶

1. 粘包与半包

1.1 粘包现象

服务端代码

  1. public class HelloWorldServer {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldServer.class);
  3.     void start() {
  4.         NioEventLoopGroup boss = new NioEventLoopGroup(1);
  5.         NioEventLoopGroup worker = new NioEventLoopGroup();
  6.         try {
  7.             ServerBootstrap serverBootstrap = new ServerBootstrap();
  8.             serverBootstrap.channel(NioServerSocketChannel.class);
  9.             serverBootstrap.group(boss, worker);
  10.             serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
  11.                 @Override
  12.                 protected void initChannel(SocketChannel ch) throws Exception {
  13.                     ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  14.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  15.                         @Override
  16.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  17.                             log.debug("connected {}", ctx.channel());
  18.                             super.channelActive(ctx);
  19.                         }
  21.                         @Override
  22.                         public void channelInactive(ChannelHandlerContext ctx) throws Exception {
  23.                             log.debug("disconnect {}", ctx.channel());
  24.                             super.channelInactive(ctx);
  25.                         }
  26.                     });
  27.                 }
  28.             });
  29.             ChannelFuture channelFuture = serverBootstrap.bind(8080);
  30.             log.debug("{} binding...", channelFuture.channel());
  31.             channelFuture.sync();
  32.             log.debug("{} bound...", channelFuture.channel());
  33.             channelFuture.channel().closeFuture().sync();
  34.         } catch (InterruptedException e) {
  35.             log.error("server error", e);
  36.         } finally {
  37.             boss.shutdownGracefully();
  38.             worker.shutdownGracefully();
  39.             log.debug("stoped");
  40.         }
  41.     }
  43.     public static void main(String[] args) {
  44.         new HelloWorldServer().start();
  45.     }
  46. }

客户端代码希望发送 10 个消息，每个消息是 16 字节

  1. public class HelloWorldClient {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);
  3.     public static void main(String[] args) {
  4.         NioEventLoopGroup worker = new NioEventLoopGroup();
  5.         try {
  6.             Bootstrap bootstrap = new Bootstrap();
  7.             bootstrap.channel(NioSocketChannel.class);
  8.             bootstrap.group(worker);
  9.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  10.                 @Override
  11.                 protected void initChannel(SocketChannel ch) throws Exception {
  12.                     log.debug("connetted...");
  13.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  14.                         @Override
  15.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  16.                             log.debug("sending...");
  17.                             Random r = new Random();
  18.                             char c = 'a';
  19.                             for (int i = 0; i < 10; i++) {
  20.                                 ByteBuf buffer = ctx.alloc().buffer();
  21.                                 buffer.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
  22.                                 ctx.writeAndFlush(buffer);
  23.                             }
  24.                         }
  25.                     });
  26.                 }
  27.             });
  28.             ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8080).sync();
  29.             channelFuture.channel().closeFuture().sync();
  31.         } catch (InterruptedException e) {
  32.             log.error("client error", e);
  33.         } finally {
  34.             worker.shutdownGracefully();
  35.         }
  36.     }
  37. }

服务器端的某次输出，可以看到一次就接收了 160 个字节，而非分 10 次接收

  1. 08:24:46 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x81e0fda5] binding...
  2. 08:24:46 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x81e0fda5, L:/0:0:0:0:0:0:0:0:8080] bound...
  3. 08:24:55 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x94132411, L:/127.0.0.1:8080 - R:/127.0.0.1:58177] REGISTERED
  4. 08:24:55 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x94132411, L:/127.0.0.1:8080 - R:/127.0.0.1:58177] ACTIVE
  5. 08:24:55 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.HelloWorldServer - connected [id: 0x94132411, L:/127.0.0.1:8080 - R:/127.0.0.1:58177]
  6. 08:24:55 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x94132411, L:/127.0.0.1:8080 - R:/127.0.0.1:58177] READ: 160B
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  11. |00000010| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  12. |00000020| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  13. |00000030| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  14. |00000040| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  15. |00000050| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  16. |00000060| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  17. |00000070| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  18. |00000080| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  19. |00000090| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  20. +--------+-------------------------------------------------+----------------+
  21. 08:24:55 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x94132411, L:/127.0.0.1:8080 - R:/127.0.0.1:58177] READ COMPLETE

1.2 半包现象

客户端代码希望发送 1 个消息，这个消息是 160 字节，代码改为

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

为现象明显，服务端修改一下接收缓冲区，其它代码不变

  1. 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

  1. 08:43:49 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x4d6c6a84] binding...
  2. 08:43:49 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x4d6c6a84, L:/0:0:0:0:0:0:0:0:8080] bound...
  3. 08:44:23 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] REGISTERED
  4. 08:44:23 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] ACTIVE
  5. 08:44:23 [DEBUG] [nioEventLoopGroup-3-1] c.i.n.HelloWorldServer - connected [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221]
  6. 08:44:24 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] READ: 20B
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |................|
  11. |00000010| 00 01 02 03                                     |....            |
  12. +--------+-------------------------------------------------+----------------+
  13. 08:44:24 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] READ COMPLETE
  14. 08:44:24 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] READ: 140B
  15.          +-------------------------------------------------+
  16.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  17. +--------+-------------------------------------------------+----------------+
  18. |00000000| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  19. |00000010| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  20. |00000020| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  21. |00000030| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  22. |00000040| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  23. |00000050| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  24. |00000060| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  25. |00000070| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 01 02 03 |................|
  26. |00000080| 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f             |............    |
  27. +--------+-------------------------------------------------+----------------+
  28. 08:44:24 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x1719abf7, L:/127.0.0.1:8080 - R:/127.0.0.1:59221] READ COMPLETE

注意

serverBootstrap.option(ChannelOption.SO_RCVBUF, 10) 影响的底层接收缓冲区（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 256 bytes 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 256 bytes 字节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 128 bytes，发送方的报文大小是 256 bytes，这时放不下了，只能先发送前 128 bytes，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，会将数据切分发送，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
    Netty03-进阶 - 图1

  • 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
    Netty03-进阶 - 图2

  • 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

    • 图中深色的部分即要发送的数据，高亮的部分即窗口
    • 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 1001~2000 这个段的数据 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 20 bytes，ip 头占用 20 bytes，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 的值在三次握手时通知对方自己 MSS 的值，然后在两者之间选择一个小值作为 MSS

Netty03-进阶 - 图3

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 41 bytes，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）则需要发送
    • 除上述情况，延迟发送

1.4 解决方案

  1. 短链接，发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，缺点效率太低
  2. 每一条消息采用固定长度，缺点浪费空间
  3. 每一条消息采用分隔符，例如 \n，缺点需要转义
  4. 每一条消息分为 head 和 body，head 中包含 body 的长度

方法1，短链接

以解决粘包为例

  1. public class HelloWorldClient {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);
  4.     public static void main(String[] args) {
  5.         // 分 10 次发送
  6.         for (int i = 0; i < 10; i++) {
  7.             send();
  8.         }
  9.     }
  11.     private static void send() {
  12.         NioEventLoopGroup worker = new NioEventLoopGroup();
  13.         try {
  14.             Bootstrap bootstrap = new Bootstrap();
  15.             bootstrap.channel(NioSocketChannel.class);
  16.             bootstrap.group(worker);
  17.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  18.                 @Override
  19.                 protected void initChannel(SocketChannel ch) throws Exception {
  20.                     log.debug("conneted...");
  21.                     ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  22.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  23.                         @Override
  24.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  25.                             log.debug("sending...");
  26.                             ByteBuf buffer = ctx.alloc().buffer();
  27.                             buffer.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
  28.                             ctx.writeAndFlush(buffer);
  29.                             // 发完即关
  30.                             ctx.close();
  31.                         }
  32.                     });
  33.                 }
  34.             });
  35.             ChannelFuture channelFuture = bootstrap.connect("localhost", 8080).sync();
  36.             channelFuture.channel().closeFuture().sync();
  38.         } catch (InterruptedException e) {
  39.             log.error("client error", e);
  40.         } finally {
  41.             worker.shutdownGracefully();
  42.         }
  43.     }
  44. }

输出，略

半包用这种办法还是不好解决，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），服务器端加入

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

客户端测试代码，注意, 采用这种方法后，客户端什么时候 flush 都可以

  1. public class HelloWorldClient {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);
  4.     public static void main(String[] args) {
  5.         NioEventLoopGroup worker = new NioEventLoopGroup();
  6.         try {
  7.             Bootstrap bootstrap = new Bootstrap();
  8.             bootstrap.channel(NioSocketChannel.class);
  9.             bootstrap.group(worker);
  10.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  11.                 @Override
  12.                 protected void initChannel(SocketChannel ch) throws Exception {
  13.                     log.debug("connetted...");
  14.                     ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  15.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  16.                         @Override
  17.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  18.                             log.debug("sending...");
  19.                             // 发送内容随机的数据包
  20.                             Random r = new Random();
  21.                             char c = 'a';
  22.                             ByteBuf buffer = ctx.alloc().buffer();
  23.                             for (int i = 0; i < 10; i++) {
  24.                                 byte[] bytes = new byte[8];
  25.                                 for (int j = 0; j < r.nextInt(8); j++) {
  26.                                     bytes[j] = (byte) c;
  27.                                 }
  28.                                 c++;
  29.                                 buffer.writeBytes(bytes);
  30.                             }
  31.                             ctx.writeAndFlush(buffer);
  32.                         }
  33.                     });
  34.                 }
  35.             });
  36.             ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
  37.             channelFuture.channel().closeFuture().sync();
  39.         } catch (InterruptedException e) {
  40.             log.error("client error", e);
  41.         } finally {
  42.             worker.shutdownGracefully();
  43.         }
  44.     }
  45. }

客户端输出

  1. 12:07:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
  2. 12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2] REGISTERED
  3. 12:07:00 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x3c2ef3c2] CONNECT: /192.168.0.103:9090
  4. 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
  5. 12:07:00 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
  6. 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
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 61 61 61 61 00 00 00 00 62 00 00 00 00 00 00 00 |aaaa....b.......|
  11. |00000010| 63 63 00 00 00 00 00 00 64 00 00 00 00 00 00 00 |cc......d.......|
  12. |00000020| 00 00 00 00 00 00 00 00 66 66 66 66 00 00 00 00 |........ffff....|
  13. |00000030| 67 67 67 00 00 00 00 00 68 00 00 00 00 00 00 00 |ggg.....h.......|
  14. |00000040| 69 69 69 69 69 00 00 00 6a 6a 6a 6a 00 00 00 00 |iiiii...jjjj....|
  15. +--------+-------------------------------------------------+----------------+
  16. 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

  1. 12:06:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xe3d9713f] binding...
  2. 12:06:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xe3d9713f, L:/192.168.0.103:9090] bound...
  3. 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
  4. 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
  5. 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]
  6. 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
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 61 61 61 61 00 00 00 00                         |aaaa....        |
  11. +--------+-------------------------------------------------+----------------+
  12. 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
  13.          +-------------------------------------------------+
  14.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  15. +--------+-------------------------------------------------+----------------+
  16. |00000000| 62 00 00 00 00 00 00 00                         |b.......        |
  17. +--------+-------------------------------------------------+----------------+
  18. 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
  19.          +-------------------------------------------------+
  20.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  21. +--------+-------------------------------------------------+----------------+
  22. |00000000| 63 63 00 00 00 00 00 00                         |cc......        |
  23. +--------+-------------------------------------------------+----------------+
  24. 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
  25.          +-------------------------------------------------+
  26.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  27. +--------+-------------------------------------------------+----------------+
  28. |00000000| 64 00 00 00 00 00 00 00                         |d.......        |
  29. +--------+-------------------------------------------------+----------------+
  30. 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
  31.          +-------------------------------------------------+
  32.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  33. +--------+-------------------------------------------------+----------------+
  34. |00000000| 00 00 00 00 00 00 00 00                         |........        |
  35. +--------+-------------------------------------------------+----------------+
  36. 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
  37.          +-------------------------------------------------+
  38.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  39. +--------+-------------------------------------------------+----------------+
  40. |00000000| 66 66 66 66 00 00 00 00                         |ffff....        |
  41. +--------+-------------------------------------------------+----------------+
  42. 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
  43.          +-------------------------------------------------+
  44.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  45. +--------+-------------------------------------------------+----------------+
  46. |00000000| 67 67 67 00 00 00 00 00                         |ggg.....        |
  47. +--------+-------------------------------------------------+----------------+
  48. 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
  49.          +-------------------------------------------------+
  50.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  51. +--------+-------------------------------------------------+----------------+
  52. |00000000| 68 00 00 00 00 00 00 00                         |h.......        |
  53. +--------+-------------------------------------------------+----------------+
  54. 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
  55.          +-------------------------------------------------+
  56.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  57. +--------+-------------------------------------------------+----------------+
  58. |00000000| 69 69 69 69 69 00 00 00                         |iiiii...        |
  59. +--------+-------------------------------------------------+----------------+
  60. 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
  61.          +-------------------------------------------------+
  62.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  63. +--------+-------------------------------------------------+----------------+
  64. |00000000| 6a 6a 6a 6a 00 00 00 00                         |jjjj....        |
  65. +--------+-------------------------------------------------+----------------+
  66. 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

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

客户端在每条消息之后，加入 \n 分隔符

  1. public class HelloWorldClient {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);
  4.     public static void main(String[] args) {
  5.         NioEventLoopGroup worker = new NioEventLoopGroup();
  6.         try {
  7.             Bootstrap bootstrap = new Bootstrap();
  8.             bootstrap.channel(NioSocketChannel.class);
  9.             bootstrap.group(worker);
  10.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  11.                 @Override
  12.                 protected void initChannel(SocketChannel ch) throws Exception {
  13.                     log.debug("connetted...");
  14.                     ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  15.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  16.                         @Override
  17.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  18.                             log.debug("sending...");
  19.                             Random r = new Random();
  20.                             char c = 'a';
  21.                             ByteBuf buffer = ctx.alloc().buffer();
  22.                             for (int i = 0; i < 10; i++) {
  23.                                 for (int j = 1; j <= r.nextInt(16)+1; j++) {
  24.                                     buffer.writeByte((byte) c);
  25.                                 }
  26.                                 buffer.writeByte(10);
  27.                                 c++;
  28.                             }
  29.                             ctx.writeAndFlush(buffer);
  30.                         }
  31.                     });
  32.                 }
  33.             });
  34.             ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
  35.             channelFuture.channel().closeFuture().sync();
  37.         } catch (InterruptedException e) {
  38.             log.error("client error", e);
  39.         } finally {
  40.             worker.shutdownGracefully();
  41.         }
  42.     }
  43. }

客户端输出

  1. 14:08:18 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
  2. 14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755] REGISTERED
  3. 14:08:18 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0x1282d755] CONNECT: /192.168.0.103:9090
  4. 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
  5. 14:08:18 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
  6. 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
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 61 0a 62 62 62 0a 63 63 63 0a 64 64 0a 65 65 65 |a.bbb.ccc.dd.eee|
  11. |00000010| 65 65 65 65 65 65 65 0a 66 66 0a 67 67 67 67 67 |eeeeeee.ff.ggggg|
  12. |00000020| 67 67 0a 68 68 68 68 0a 69 69 69 69 69 69 69 0a |gg.hhhh.iiiiiii.|
  13. |00000030| 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 0a             |jjjjjjjjjjj.    |
  14. +--------+-------------------------------------------------+----------------+
  15. 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

服务端输出

  1. 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]
  2. 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
  3.          +-------------------------------------------------+
  4.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  5. +--------+-------------------------------------------------+----------------+
  6. |00000000| 61                                              |a               |
  7. +--------+-------------------------------------------------+----------------+
  8. 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
  9.          +-------------------------------------------------+
  10.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  11. +--------+-------------------------------------------------+----------------+
  12. |00000000| 62 62 62                                        |bbb             |
  13. +--------+-------------------------------------------------+----------------+
  14. 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
  15.          +-------------------------------------------------+
  16.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  17. +--------+-------------------------------------------------+----------------+
  18. |00000000| 63 63 63                                        |ccc             |
  19. +--------+-------------------------------------------------+----------------+
  20. 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
  21.          +-------------------------------------------------+
  22.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  23. +--------+-------------------------------------------------+----------------+
  24. |00000000| 64 64                                           |dd              |
  25. +--------+-------------------------------------------------+----------------+
  26. 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
  27.          +-------------------------------------------------+
  28.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  29. +--------+-------------------------------------------------+----------------+
  30. |00000000| 65 65 65 65 65 65 65 65 65 65                   |eeeeeeeeee      |
  31. +--------+-------------------------------------------------+----------------+
  32. 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
  33.          +-------------------------------------------------+
  34.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  35. +--------+-------------------------------------------------+----------------+
  36. |00000000| 66 66                                           |ff              |
  37. +--------+-------------------------------------------------+----------------+
  38. 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
  39.          +-------------------------------------------------+
  40.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  41. +--------+-------------------------------------------------+----------------+
  42. |00000000| 67 67 67 67 67 67 67                            |ggggggg         |
  43. +--------+-------------------------------------------------+----------------+
  44. 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
  45.          +-------------------------------------------------+
  46.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  47. +--------+-------------------------------------------------+----------------+
  48. |00000000| 68 68 68 68                                     |hhhh            |
  49. +--------+-------------------------------------------------+----------------+
  50. 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
  51.          +-------------------------------------------------+
  52.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  53. +--------+-------------------------------------------------+----------------+
  54. |00000000| 69 69 69 69 69 69 69                            |iiiiiii         |
  55. +--------+-------------------------------------------------+----------------+
  56. 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
  57.          +-------------------------------------------------+
  58.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  59. +--------+-------------------------------------------------+----------------+
  60. |00000000| 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a 6a                |jjjjjjjjjjj     |
  61. +--------+-------------------------------------------------+----------------+
  62. 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

缺点，处理字符数据比较合适，但如果内容本身包含了分隔符（字节数据常常会有此情况），那么就会解析错误

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数据的长度

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

客户端代码

  1. public class HelloWorldClient {
  2.     static final Logger log = LoggerFactory.getLogger(HelloWorldClient.class);
  4.     public static void main(String[] args) {
  5.         NioEventLoopGroup worker = new NioEventLoopGroup();
  6.         try {
  7.             Bootstrap bootstrap = new Bootstrap();
  8.             bootstrap.channel(NioSocketChannel.class);
  9.             bootstrap.group(worker);
  10.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  11.                 @Override
  12.                 protected void initChannel(SocketChannel ch) throws Exception {
  13.                     log.debug("connetted...");
  14.                     ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  15.                     ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  16.                         @Override
  17.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  18.                             log.debug("sending...");
  19.                             Random r = new Random();
  20.                             char c = 'a';
  21.                             ByteBuf buffer = ctx.alloc().buffer();
  22.                             for (int i = 0; i < 10; i++) {
  23.                                 byte length = (byte) (r.nextInt(16) + 1);
  24.                                 // 先写入长度
  25.                                 buffer.writeByte(length);
  26.                                 // 再
  27.                                 for (int j = 1; j <= length; j++) {
  28.                                     buffer.writeByte((byte) c);
  29.                                 }
  30.                                 c++;
  31.                             }
  32.                             ctx.writeAndFlush(buffer);
  33.                         }
  34.                     });
  35.                 }
  36.             });
  37.             ChannelFuture channelFuture = bootstrap.connect("192.168.0.103", 9090).sync();
  38.             channelFuture.channel().closeFuture().sync();
  40.         } catch (InterruptedException e) {
  41.             log.error("client error", e);
  42.         } finally {
  43.             worker.shutdownGracefully();
  44.         }
  45.     }
  46. }

客户端输出

  1. 14:37:10 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - connetted...
  2. 14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8] REGISTERED
  3. 14:37:10 [DEBUG] [nioEventLoopGroup-2-1] i.n.h.l.LoggingHandler - [id: 0xf0f347b8] CONNECT: /192.168.0.103:9090
  4. 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
  5. 14:37:10 [DEBUG] [nioEventLoopGroup-2-1] c.i.n.HelloWorldClient - sending...
  6. 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
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 09 61 61 61 61 61 61 61 61 61 09 62 62 62 62 62 |.aaaaaaaaa.bbbbb|
  11. |00000010| 62 62 62 62 06 63 63 63 63 63 63 08 64 64 64 64 |bbbb.cccccc.dddd|
  12. |00000020| 64 64 64 64 0f 65 65 65 65 65 65 65 65 65 65 65 |dddd.eeeeeeeeeee|
  13. |00000030| 65 65 65 65 0d 66 66 66 66 66 66 66 66 66 66 66 |eeee.fffffffffff|
  14. |00000040| 66 66 02 67 67 02 68 68 0e 69 69 69 69 69 69 69 |ff.gg.hh.iiiiiii|
  15. |00000050| 69 69 69 69 69 69 69 09 6a 6a 6a 6a 6a 6a 6a 6a |iiiiiii.jjjjjjjj|
  16. |00000060| 6a                                              |j               |
  17. +--------+-------------------------------------------------+----------------+
  18. 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

  1. 14:36:50 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xdff439d3] binding...
  2. 14:36:51 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0xdff439d3, L:/192.168.0.103:9090] bound...
  3. 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
  4. 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
  5. 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]
  6. 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
  7.          +-------------------------------------------------+
  8.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  9. +--------+-------------------------------------------------+----------------+
  10. |00000000| 61 61 61 61 61 61 61 61 61                      |aaaaaaaaa       |
  11. +--------+-------------------------------------------------+----------------+
  12. 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
  13.          +-------------------------------------------------+
  14.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  15. +--------+-------------------------------------------------+----------------+
  16. |00000000| 62 62 62 62 62 62 62 62 62                      |bbbbbbbbb       |
  17. +--------+-------------------------------------------------+----------------+
  18. 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
  19.          +-------------------------------------------------+
  20.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  21. +--------+-------------------------------------------------+----------------+
  22. |00000000| 63 63 63 63 63 63                               |cccccc          |
  23. +--------+-------------------------------------------------+----------------+
  24. 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
  25.          +-------------------------------------------------+
  26.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  27. +--------+-------------------------------------------------+----------------+
  28. |00000000| 64 64 64 64 64 64 64 64                         |dddddddd        |
  29. +--------+-------------------------------------------------+----------------+
  30. 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
  31.          +-------------------------------------------------+
  32.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  33. +--------+-------------------------------------------------+----------------+
  34. |00000000| 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65    |eeeeeeeeeeeeeee |
  35. +--------+-------------------------------------------------+----------------+
  36. 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
  37.          +-------------------------------------------------+
  38.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  39. +--------+-------------------------------------------------+----------------+
  40. |00000000| 66 66 66 66 66 66 66 66 66 66 66 66 66          |fffffffffffff   |
  41. +--------+-------------------------------------------------+----------------+
  42. 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
  43.          +-------------------------------------------------+
  44.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  45. +--------+-------------------------------------------------+----------------+
  46. |00000000| 67 67                                           |gg              |
  47. +--------+-------------------------------------------------+----------------+
  48. 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
  49.          +-------------------------------------------------+
  50.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  51. +--------+-------------------------------------------------+----------------+
  52. |00000000| 68 68                                           |hh              |
  53. +--------+-------------------------------------------------+----------------+
  54. 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
  55.          +-------------------------------------------------+
  56.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  57. +--------+-------------------------------------------------+----------------+
  58. |00000000| 69 69 69 69 69 69 69 69 69 69 69 69 69 69       |iiiiiiiiiiiiii  |
  59. +--------+-------------------------------------------------+----------------+
  60. 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
  61.          +-------------------------------------------------+
  62.          |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
  63. +--------+-------------------------------------------------+----------------+
  64. |00000000| 6a 6a 6a 6a 6a 6a 6a 6a 6a                      |jjjjjjjjj       |
  65. +--------+-------------------------------------------------+----------------+
  66. 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

  1. 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

  1. 下雨天留客，天留，我不留

另一种解读

  1. 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用

  1. 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，发送信息方式如下，就不会被接收方弄错意思了

  1. 0f下雨天留客06天留09我不留

小故事

很久很久以前，一位私塾先生到一家任教。双方签订了一纸协议：“无鸡鸭亦可无鱼肉亦可白菜豆腐不可少不得束修金”。此后，私塾先生虽然认真教课，但主人家则总是给私塾先生以白菜豆腐为菜，丝毫未见鸡鸭鱼肉的款待。私塾先生先是很不解，可是后来也就想通了：主人把鸡鸭鱼肉的钱都会换为束修金的，也罢。至此双方相安无事。

年关将至，一个学年段亦告结束。私塾先生临行时，也不见主人家为他交付束修金，遂与主家理论。然主家亦振振有词：“有协议为证——无鸡鸭亦可，无鱼肉亦可，白菜豆腐不可少，不得束修金。这白纸黑字明摆着的，你有什么要说的呢？”

私塾先生据理力争：“协议是这样的——无鸡，鸭亦可；无鱼，肉亦可；白菜豆腐不可，少不得束修金。”

双方唇枪舌战，你来我往，真个是不亦乐乎！

这里的束修金，也作“束脩”，应当是泛指教师应当得到的报酬

2.2 redis 协议举例

  1. NioEventLoopGroup worker = new NioEventLoopGroup();
  2. byte[] LINE = {13, 10};
  3. try {
  4.     Bootstrap bootstrap = new Bootstrap();
  5.     bootstrap.channel(NioSocketChannel.class);
  6.     bootstrap.group(worker);
  7.     bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  8.         @Override
  9.         protected void initChannel(SocketChannel ch) {
  10.             ch.pipeline().addLast(new LoggingHandler());
  11.             ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  12.                 // 会在连接 channel 建立成功后，会触发 active 事件
  13.                 @Override
  14.                 public void channelActive(ChannelHandlerContext ctx) {
  15.                     set(ctx);
  16.                     get(ctx);
  17.                 }
  18.                 private void get(ChannelHandlerContext ctx) {
  19.                     ByteBuf buf = ctx.alloc().buffer();
  20.                     buf.writeBytes("*2".getBytes());
  21.                     buf.writeBytes(LINE);
  22.                     buf.writeBytes("$3".getBytes());
  23.                     buf.writeBytes(LINE);
  24.                     buf.writeBytes("get".getBytes());
  25.                     buf.writeBytes(LINE);
  26.                     buf.writeBytes("$3".getBytes());
  27.                     buf.writeBytes(LINE);
  28.                     buf.writeBytes("aaa".getBytes());
  29.                     buf.writeBytes(LINE);
  30.                     ctx.writeAndFlush(buf);
  31.                 }
  32.                 private void set(ChannelHandlerContext ctx) {
  33.                     ByteBuf buf = ctx.alloc().buffer();
  34.                     buf.writeBytes("*3".getBytes());
  35.                     buf.writeBytes(LINE);
  36.                     buf.writeBytes("$3".getBytes());
  37.                     buf.writeBytes(LINE);
  38.                     buf.writeBytes("set".getBytes());
  39.                     buf.writeBytes(LINE);
  40.                     buf.writeBytes("$3".getBytes());
  41.                     buf.writeBytes(LINE);
  42.                     buf.writeBytes("aaa".getBytes());
  43.                     buf.writeBytes(LINE);
  44.                     buf.writeBytes("$3".getBytes());
  45.                     buf.writeBytes(LINE);
  46.                     buf.writeBytes("bbb".getBytes());
  47.                     buf.writeBytes(LINE);
  48.                     ctx.writeAndFlush(buf);
  49.                 }
  51.                 @Override
  52.                 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
  53.                     ByteBuf buf = (ByteBuf) msg;
  54.                     System.out.println(buf.toString(Charset.defaultCharset()));
  55.                 }
  56.             });
  57.         }
  58.     });
  59.     ChannelFuture channelFuture = bootstrap.connect("localhost", 6379).sync();
  60.     channelFuture.channel().closeFuture().sync();
  61. } catch (InterruptedException e) {
  62.     log.error("client error", e);
  63. } finally {
  64.     worker.shutdownGracefully();
  65. }

2.3 http 协议举例

  1. NioEventLoopGroup boss = new NioEventLoopGroup();
  2. NioEventLoopGroup worker = new NioEventLoopGroup();
  3. try {
  4.     ServerBootstrap serverBootstrap = new ServerBootstrap();
  5.     serverBootstrap.channel(NioServerSocketChannel.class);
  6.     serverBootstrap.group(boss, worker);
  7.     serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
  8.         @Override
  9.         protected void initChannel(SocketChannel ch) throws Exception {
  10.             ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
  11.             ch.pipeline().addLast(new HttpServerCodec());
  12.             ch.pipeline().addLast(new SimpleChannelInboundHandler<HttpRequest>() {
  13.                 @Override
  14.                 protected void channelRead0(ChannelHandlerContext ctx, HttpRequest msg) throws Exception {
  15.                     // 获取请求
  16.                     log.debug(msg.uri());
  18.                     // 返回响应
  19.                     DefaultFullHttpResponse response =
  20.                             new DefaultFullHttpResponse(msg.protocolVersion(), HttpResponseStatus.OK);
  22.                     byte[] bytes = "<h1>Hello, world!</h1>".getBytes();
  24.                     response.headers().setInt(CONTENT_LENGTH, bytes.length);
  25.                     response.content().writeBytes(bytes);
  27.                     // 写回响应
  28.                     ctx.writeAndFlush(response);
  29.                 }
  30.             });
  31.             /*ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
  32.                 @Override
  33.                 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
  34.                     log.debug("{}", msg.getClass());
  36.                     if (msg instanceof HttpRequest) { // 请求行，请求头
  38.                     } else if (msg instanceof HttpContent) { //请求体
  40.                     }
  41.                 }
  42.             });*/
  43.         }
  44.     });
  45.     ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
  46.     channelFuture.channel().closeFuture().sync();
  47. } catch (InterruptedException e) {
  48.     log.error("server error", e);
  49. } finally {
  50.     boss.shutdownGracefully();
  51.     worker.shutdownGracefully();
  52. }

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

  1. @Slf4j
  2. public class MessageCodec extends ByteToMessageCodec<Message> {
  4.     @Override
  5.     protected void encode(ChannelHandlerContext ctx, Message msg, ByteBuf out) throws Exception {
  6.         // 1. 4 字节的魔数
  7.         out.writeBytes(new byte[]{1, 2, 3, 4});
  8.         // 2. 1 字节的版本,
  9.         out.writeByte(1);
  10.         // 3. 1 字节的序列化方式 jdk 0 , json 1
  11.         out.writeByte(0);
  12.         // 4. 1 字节的指令类型
  13.         out.writeByte(msg.getMessageType());
  14.         // 5. 4 个字节
  15.         out.writeInt(msg.getSequenceId());
  16.         // 无意义，对齐填充
  17.         out.writeByte(0xff);
  18.         // 6. 获取内容的字节数组
  19.         ByteArrayOutputStream bos = new ByteArrayOutputStream();
  20.         ObjectOutputStream oos = new ObjectOutputStream(bos);
  21.         oos.writeObject(msg);
  22.         byte[] bytes = bos.toByteArray();
  23.         // 7. 长度
  24.         out.writeInt(bytes.length);
  25.         // 8. 写入内容
  26.         out.writeBytes(bytes);
  27.     }
  29.     @Override
  30.     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
  31.         int magicNum = in.readInt();
  32.         byte version = in.readByte();
  33.         byte serializerType = in.readByte();
  34.         byte messageType = in.readByte();
  35.         int sequenceId = in.readInt();
  36.         in.readByte();
  37.         int length = in.readInt();
  38.         byte[] bytes = new byte[length];
  39.         in.readBytes(bytes, 0, length);
  40.         ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bytes));
  41.         Message message = (Message) ois.readObject();
  42.         log.debug("{}, {}, {}, {}, {}, {}", magicNum, version, serializerType, messageType, sequenceId, length);
  43.         log.debug("{}", message);
  44.         out.add(message);
  45.     }
  46. }

测试

  1. EmbeddedChannel channel = new EmbeddedChannel(
  2.     new LoggingHandler(),
  3.     new LengthFieldBasedFrameDecoder(
  4.         1024, 12, 4, 0, 0),
  5.     new MessageCodec()
  6. );
  7. // encode
  8. LoginRequestMessage message = new LoginRequestMessage("zhangsan", "123", "张三");
  9. //        channel.writeOutbound(message);
  10. // decode
  11. ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
  12. new MessageCodec().encode(null, message, buf);
  14. ByteBuf s1 = buf.slice(0, 100);
  15. ByteBuf s2 = buf.slice(100, buf.readableBytes() - 100);
  16. s1.retain(); // 引用计数 2
  17. channel.writeInbound(s1); // release 1
  18. channel.writeInbound(s2);

解读

Netty03-进阶 - 图4

💡 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
  1. @Slf4j
  2. @ChannelHandler.Sharable
  3. /**
  4.  * 必须和 LengthFieldBasedFrameDecoder 一起使用，确保接到的 ByteBuf 消息是完整的
  5.  */
  6. public class MessageCodecSharable extends MessageToMessageCodec<ByteBuf, Message> {
  7.     @Override
  8.     protected void encode(ChannelHandlerContext ctx, Message msg, List<Object> outList) throws Exception {
  9.         ByteBuf out = ctx.alloc().buffer();
  10.         // 1. 4 字节的魔数
  11.         out.writeBytes(new byte[]{1, 2, 3, 4});
  12.         // 2. 1 字节的版本,
  13.         out.writeByte(1);
  14.         // 3. 1 字节的序列化方式 jdk 0 , json 1
  15.         out.writeByte(0);
  16.         // 4. 1 字节的指令类型
  17.         out.writeByte(msg.getMessageType());
  18.         // 5. 4 个字节
  19.         out.writeInt(msg.getSequenceId());
  20.         // 无意义，对齐填充
  21.         out.writeByte(0xff);
  22.         // 6. 获取内容的字节数组
  23.         ByteArrayOutputStream bos = new ByteArrayOutputStream();
  24.         ObjectOutputStream oos = new ObjectOutputStream(bos);
  25.         oos.writeObject(msg);
  26.         byte[] bytes = bos.toByteArray();
  27.         // 7. 长度
  28.         out.writeInt(bytes.length);
  29.         // 8. 写入内容
  30.         out.writeBytes(bytes);
  31.         outList.add(out);
  32.     }
  34.     @Override
  35.     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
  36.         int magicNum = in.readInt();
  37.         byte version = in.readByte();
  38.         byte serializerType = in.readByte();
  39.         byte messageType = in.readByte();
  40.         int sequenceId = in.readInt();
  41.         in.readByte();
  42.         int length = in.readInt();
  43.         byte[] bytes = new byte[length];
  44.         in.readBytes(bytes, 0, length);
  45.         ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bytes));
  46.         Message message = (Message) ois.readObject();
  47.         log.debug("{}, {}, {}, {}, {}, {}", magicNum, version, serializerType, messageType, sequenceId, length);
  48.         log.debug("{}", message);
  49.         out.add(message);
  50.     }
  51. }

3. 聊天室案例

3.1 聊天室业务介绍

  1. /**
  2.  * 用户管理接口
  3.  */
  4. public interface UserService {
  6.     /**
  7.      * 登录
  8.      * @param username 用户名
  9.      * @param password 密码
  10.      * @return 登录成功返回 true, 否则返回 false
  11.      */
  12.     boolean login(String username, String password);
  13. }
  1. /**
  2.  * 会话管理接口
  3.  */
  4. public interface Session {
  6.     /**
  7.      * 绑定会话
  8.      * @param channel 哪个 channel 要绑定会话
  9.      * @param username 会话绑定用户
  10.      */
  11.     void bind(Channel channel, String username);
  13.     /**
  14.      * 解绑会话
  15.      * @param channel 哪个 channel 要解绑会话
  16.      */
  17.     void unbind(Channel channel);
  19.     /**
  20.      * 获取属性
  21.      * @param channel 哪个 channel
  22.      * @param name 属性名
  23.      * @return 属性值
  24.      */
  25.     Object getAttribute(Channel channel, String name);
  27.     /**
  28.      * 设置属性
  29.      * @param channel 哪个 channel
  30.      * @param name 属性名
  31.      * @param value 属性值
  32.      */
  33.     void setAttribute(Channel channel, String name, Object value);
  35.     /**
  36.      * 根据用户名获取 channel
  37.      * @param username 用户名
  38.      * @return channel
  39.      */
  40.     Channel getChannel(String username);
  41. }
  1. /**
  2.  * 聊天组会话管理接口
  3.  */
  4. public interface GroupSession {
  6.     /**
  7.      * 创建一个聊天组, 如果不存在才能创建成功, 否则返回 null
  8.      * @param name 组名
  9.      * @param members 成员
  10.      * @return 成功时返回组对象, 失败返回 null
  11.      */
  12.     Group createGroup(String name, Set<String> members);
  14.     /**
  15.      * 加入聊天组
  16.      * @param name 组名
  17.      * @param member 成员名
  18.      * @return 如果组不存在返回 null, 否则返回组对象
  19.      */
  20.     Group joinMember(String name, String member);
  22.     /**
  23.      * 移除组成员
  24.      * @param name 组名
  25.      * @param member 成员名
  26.      * @return 如果组不存在返回 null, 否则返回组对象
  27.      */
  28.     Group removeMember(String name, String member);
  30.     /**
  31.      * 移除聊天组
  32.      * @param name 组名
  33.      * @return 如果组不存在返回 null, 否则返回组对象
  34.      */
  35.     Group removeGroup(String name);
  37.     /**
  38.      * 获取组成员
  39.      * @param name 组名
  40.      * @return 成员集合, 没有成员会返回 empty set
  41.      */
  42.     Set<String> getMembers(String name);
  44.     /**
  45.      * 获取组成员的 channel 集合, 只有在线的 channel 才会返回
  46.      * @param name 组名
  47.      * @return 成员 channel 集合
  48.      */
  49.     List<Channel> getMembersChannel(String name);
  50. }

3.2 聊天室业务-登录

  1. @Slf4j
  2. public class ChatServer {
  3.     public static void main(String[] args) {
  4.         NioEventLoopGroup boss = new NioEventLoopGroup();
  5.         NioEventLoopGroup worker = new NioEventLoopGroup();
  6.         LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
  7.         MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();
  8.         try {
  9.             ServerBootstrap serverBootstrap = new ServerBootstrap();
  10.             serverBootstrap.channel(NioServerSocketChannel.class);
  11.             serverBootstrap.group(boss, worker);
  12.             serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
  13.                 @Override
  14.                 protected void initChannel(SocketChannel ch) throws Exception {
  15.                     ch.pipeline().addLast(new ProcotolFrameDecoder());
  16.                     ch.pipeline().addLast(LOGGING_HANDLER);
  17.                     ch.pipeline().addLast(MESSAGE_CODEC);
  18.                     ch.pipeline().addLast(new SimpleChannelInboundHandler<LoginRequestMessage>() {
  19.                         @Override
  20.                         protected void channelRead0(ChannelHandlerContext ctx, LoginRequestMessage msg) throws Exception {
  21.                             String username = msg.getUsername();
  22.                             String password = msg.getPassword();
  23.                             boolean login = UserServiceFactory.getUserService().login(username, password);
  24.                             LoginResponseMessage message;
  25.                             if(login) {
  26.                                 message = new LoginResponseMessage(true, "登录成功");
  27.                             } else {
  28.                                 message = new LoginResponseMessage(false, "用户名或密码不正确");
  29.                             }
  30.                             ctx.writeAndFlush(message);
  31.                         }
  32.                     });
  33.                 }
  34.             });
  35.             Channel channel = serverBootstrap.bind(8080).sync().channel();
  36.             channel.closeFuture().sync();
  37.         } catch (InterruptedException e) {
  38.             log.error("server error", e);
  39.         } finally {
  40.             boss.shutdownGracefully();
  41.             worker.shutdownGracefully();
  42.         }
  43.     }
  44. }
  1. @Slf4j
  2. public class ChatClient {
  3.     public static void main(String[] args) {
  4.         NioEventLoopGroup group = new NioEventLoopGroup();
  5.         LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
  6.         MessageCodecSharable MESSAGE_CODEC = new MessageCodecSharable();
  7.         CountDownLatch WAIT_FOR_LOGIN = new CountDownLatch(1);
  8.         AtomicBoolean LOGIN = new AtomicBoolean(false);
  9.         try {
  10.             Bootstrap bootstrap = new Bootstrap();
  11.             bootstrap.channel(NioSocketChannel.class);
  12.             bootstrap.group(group);
  13.             bootstrap.handler(new ChannelInitializer<SocketChannel>() {
  14.                 @Override
  15.                 protected void initChannel(SocketChannel ch) throws Exception {
  16.                     ch.pipeline().addLast(new ProcotolFrameDecoder());
  17. //                    ch.pipeline().addLast(LOGGING_HANDLER);
  18.                     ch.pipeline().addLast(MESSAGE_CODEC);
  19.                     ch.pipeline().addLast("client handler", new ChannelInboundHandlerAdapter() {
  20.                         // 接收响应消息
  21.                         @Override
  22.                         public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
  23.                             log.debug("msg: {}", msg);
  24.                             if ((msg instanceof LoginResponseMessage)) {
  25.                                 LoginResponseMessage response = (LoginResponseMessage) msg;
  26.                                 if (response.isSuccess()) {
  27.                                     // 如果登录成功
  28.                                     LOGIN.set(true);
  29.                                 }
  30.                                 // 唤醒 system in 线程
  31.                                 WAIT_FOR_LOGIN.countDown();
  32.                             }
  33.                         }
  35.                         // 在连接建立后触发 active 事件
  36.                         @Override
  37.                         public void channelActive(ChannelHandlerContext ctx) throws Exception {
  38.                             // 负责接收用户在控制台的输入，负责向服务器发送各种消息
  39.                             new Thread(() -> {
  40.                                 Scanner scanner = new Scanner(System.in);
  41.                                 System.out.println("请输入用户名:");
  42.                                 String username = scanner.nextLine();
  43.                                 System.out.println("请输入密码:");
  44.                                 String password = scanner.nextLine();
  45.                                 // 构造消息对象
  46.                                 LoginRequestMessage message = new LoginRequestMessage(username, password);
  47.                                 // 发送消息
  48.                                 ctx.writeAndFlush(message);
  49.                                 System.out.println("等待后续操作...");
  50.                                 try {
  51.                                     WAIT_FOR_LOGIN.await();
  52.                                 } catch (InterruptedException e) {
  53.                                     e.printStackTrace();
  54.                                 }
  55.                                 // 如果登录失败
  56.                                 if (!LOGIN.get()) {
  57.                                     ctx.channel().close();
  58.                                     return;
  59.                                 }
  60.                                 while (true) {
  61.                                     System.out.println("==================================");
  62.                                     System.out.println("send [username] [content]");
  63.                                     System.out.println("gsend [group name] [content]");
  64.                                     System.out.println("gcreate [group name] [m1,m2,m3...]");
  65.                                     System.out.println("gmembers [group name]");
  66.                                     System.out.println("gjoin [group name]");
  67.                                     System.out.println("gquit [group name]");
  68.                                     System.out.println("quit");
  69.                                     System.out.println("==================================");
  70.                                     String command = scanner.nextLine();
  71.                                     String[] s = command.split(" ");
  72.                                     switch (s[0]){
  73.                                         case "send":
  74.                                             ctx.writeAndFlush(new ChatRequestMessage(username, s[1], s[2]));
  75.                                             break;
  76.                                         case "gsend":
  77.                                             ctx.writeAndFlush(new GroupChatRequestMessage(username, s[1], s[2]));
  78.                                             break;
  79.                                         case "gcreate":
  80.                                             Set<String> set = new HashSet<>(Arrays.asList(s[2].split(",")));
  81.                                             set.add(username); // 加入自己
  82.                                             ctx.writeAndFlush(new GroupCreateRequestMessage(s[1], set));
  83.                                             break;
  84.                                         case "gmembers":
  85.                                             ctx.writeAndFlush(new GroupMembersRequestMessage(s[1]));
  86.                                             break;
  87.                                         case "gjoin":
  88.                                             ctx.writeAndFlush(new GroupJoinRequestMessage(username, s[1]));
  89.                                             break;
  90.                                         case "gquit":
  91.                                             ctx.writeAndFlush(new GroupQuitRequestMessage(username, s[1]));
  92.                                             break;
  93.                                         case "quit":
  94.                                             ctx.channel().close();
  95.                                             return;
  96.                                     }
  97.                                 }
  98.                             }, "system in").start();
  99.                         }
  100.                     });
  101.                 }
  102.             });
  103.             Channel channel = bootstrap.connect("localhost", 8080).sync().channel();
  104.             channel.closeFuture().sync();
  105.         } catch (Exception e) {
  106.             log.error("client error", e);
  107.         } finally {
  108.             group.shutdownGracefully();
  109.         }
  110.     }
  111. }

3.3 聊天室业务-单聊

服务器端将 handler 独立出来

登录 handler

  1. @ChannelHandler.Sharable
  2. public class LoginRequestMessageHandler extends SimpleChannelInboundHandler<LoginRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, LoginRequestMessage msg) throws Exception {
  5.         String username = msg.getUsername();
  6.         String password = msg.getPassword();
  7.         boolean login = UserServiceFactory.getUserService().login(username, password);
  8.         LoginResponseMessage message;
  9.         if(login) {
  10.             SessionFactory.getSession().bind(ctx.channel(), username);
  11.             message = new LoginResponseMessage(true, "登录成功");
  12.         } else {
  13.             message = new LoginResponseMessage(false, "用户名或密码不正确");
  14.         }
  15.         ctx.writeAndFlush(message);
  16.     }
  17. }

单聊 handler

  1. @ChannelHandler.Sharable
  2. public class ChatRequestMessageHandler extends SimpleChannelInboundHandler<ChatRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, ChatRequestMessage msg) throws Exception {
  5.         String to = msg.getTo();
  6.         Channel channel = SessionFactory.getSession().getChannel(to);
  7.         // 在线
  8.         if(channel != null) {
  9.             channel.writeAndFlush(new ChatResponseMessage(msg.getFrom(), msg.getContent()));
  10.         }
  11.         // 不在线
  12.         else {
  13.             ctx.writeAndFlush(new ChatResponseMessage(false, "对方用户不存在或者不在线"));
  14.         }
  15.     }
  16. }

3.4 聊天室业务-群聊

创建群聊

  1. @ChannelHandler.Sharable
  2. public class GroupCreateRequestMessageHandler extends SimpleChannelInboundHandler<GroupCreateRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, GroupCreateRequestMessage msg) throws Exception {
  5.         String groupName = msg.getGroupName();
  6.         Set<String> members = msg.getMembers();
  7.         // 群管理器
  8.         GroupSession groupSession = GroupSessionFactory.getGroupSession();
  9.         Group group = groupSession.createGroup(groupName, members);
  10.         if (group == null) {
  11.             // 发生成功消息
  12.             ctx.writeAndFlush(new GroupCreateResponseMessage(true, groupName + "创建成功"));
  13.             // 发送拉群消息
  14.             List<Channel> channels = groupSession.getMembersChannel(groupName);
  15.             for (Channel channel : channels) {
  16.                 channel.writeAndFlush(new GroupCreateResponseMessage(true, "您已被拉入" + groupName));
  17.             }
  18.         } else {
  19.             ctx.writeAndFlush(new GroupCreateResponseMessage(false, groupName + "已经存在"));
  20.         }
  21.     }
  22. }

群聊

  1. @ChannelHandler.Sharable
  2. public class GroupChatRequestMessageHandler extends SimpleChannelInboundHandler<GroupChatRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, GroupChatRequestMessage msg) throws Exception {
  5.         List<Channel> channels = GroupSessionFactory.getGroupSession()
  6.                 .getMembersChannel(msg.getGroupName());
  8.         for (Channel channel : channels) {
  9.             channel.writeAndFlush(new GroupChatResponseMessage(msg.getFrom(), msg.getContent()));
  10.         }
  11.     }
  12. }

加入群聊

  1. @ChannelHandler.Sharable
  2. public class GroupJoinRequestMessageHandler extends SimpleChannelInboundHandler<GroupJoinRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, GroupJoinRequestMessage msg) throws Exception {
  5.         Group group = GroupSessionFactory.getGroupSession().joinMember(msg.getGroupName(), msg.getUsername());
  6.         if (group != null) {
  7.             ctx.writeAndFlush(new GroupJoinResponseMessage(true, msg.getGroupName() + "群加入成功"));
  8.         } else {
  9.             ctx.writeAndFlush(new GroupJoinResponseMessage(true, msg.getGroupName() + "群不存在"));
  10.         }
  11.     }
  12. }

退出群聊

  1. @ChannelHandler.Sharable
  2. public class GroupQuitRequestMessageHandler extends SimpleChannelInboundHandler<GroupQuitRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, GroupQuitRequestMessage msg) throws Exception {
  5.         Group group = GroupSessionFactory.getGroupSession().removeMember(msg.getGroupName(), msg.getUsername());
  6.         if (group != null) {
  7.             ctx.writeAndFlush(new GroupJoinResponseMessage(true, "已退出群" + msg.getGroupName()));
  8.         } else {
  9.             ctx.writeAndFlush(new GroupJoinResponseMessage(true, msg.getGroupName() + "群不存在"));
  10.         }
  11.     }
  12. }

查看成员

  1. @ChannelHandler.Sharable
  2. public class GroupMembersRequestMessageHandler extends SimpleChannelInboundHandler<GroupMembersRequestMessage> {
  3.     @Override
  4.     protected void channelRead0(ChannelHandlerContext ctx, GroupMembersRequestMessage msg) throws Exception {
  5.         Set<String> members = GroupSessionFactory.getGroupSession()
  6.                 .getMembers(msg.getGroupName());
  7.         ctx.writeAndFlush(new GroupMembersResponseMessage(members));
  8.     }
  9. }

3.5 聊天室业务-退出

  1. @Slf4j
  2. @ChannelHandler.Sharable
  3. public class QuitHandler extends ChannelInboundHandlerAdapter {
  5.     // 当连接断开时触发 inactive 事件
  6.     @Override
  7.     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
  8.         SessionFactory.getSession().unbind(ctx.channel());
  9.         log.debug("{} 已经断开", ctx.channel());
  10.     }
  12.     // 当出现异常时触发
  13.     @Override
  14.     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
  15.         SessionFactory.getSession().unbind(ctx.channel());
  16.         log.debug("{} 已经异常断开 异常是{}", ctx.channel(), cause.getMessage());
  17.     }
  18. }

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，没有就可以判定为连接假死
  1. // 用来判断是不是 读空闲时间过长，或 写空闲时间过长
  2. // 5s 内如果没有收到 channel 的数据，会触发一个 IdleState#READER_IDLE 事件
  3. ch.pipeline().addLast(new IdleStateHandler(5, 0, 0));
  4. // ChannelDuplexHandler 可以同时作为入站和出站处理器
  5. ch.pipeline().addLast(new ChannelDuplexHandler() {
  6.     // 用来触发特殊事件
  7.     @Override
  8.     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception{
  9.         IdleStateEvent event = (IdleStateEvent) evt;
  10.         // 触发了读空闲事件
  11.         if (event.state() == IdleState.READER_IDLE) {
  12.             log.debug("已经 5s 没有读到数据了");
  13.             ctx.channel().close();
  14.         }
  15.     }
  16. });

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. // 用来判断是不是 读空闲时间过长，或 写空闲时间过长
  2. // 3s 内如果没有向服务器写数据，会触发一个 IdleState#WRITER_IDLE 事件
  3. ch.pipeline().addLast(new IdleStateHandler(0, 3, 0));
  4. // ChannelDuplexHandler 可以同时作为入站和出站处理器
  5. ch.pipeline().addLast(new ChannelDuplexHandler() {
  6.     // 用来触发特殊事件
  7.     @Override
  8.     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception{
  9.         IdleStateEvent event = (IdleStateEvent) evt;
  10.         // 触发了写空闲事件
  11.         if (event.state() == IdleState.WRITER_IDLE) {
  12.             //                                log.debug("3s 没有写数据了，发送一个心跳包");
  13.             ctx.writeAndFlush(new PingMessage());
  14.         }
  15.     }
  16. });