1 粘包现象
服务端代码
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() { @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(); } }
客户端代码希望发送 10 个消息，每个消息是 16 字节
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 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(); 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("127.0.0.1", 8080).sync(); channelFuture.channel().closeFuture().sync(); } catch (InterruptedException e) { log.error("client error", e); } finally { worker.shutdownGracefully(); } } }
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
08:24:46 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x81e0fda5] binding... 08:24:46 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x81e0fda5, L:/0:0:0:0:0:0:0:0:8080] bound... 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 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 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] 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 +-------------------------------------------------+ | 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 |................| +--------+-------------------------------------------------+----------------+ 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
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
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，服务端修改一下接收缓冲区，其它代码不变
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
08:43:49 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x4d6c6a84] binding... 08:43:49 [DEBUG] [main] c.i.n.HelloWorldServer - [id: 0x4d6c6a84, L:/0:0:0:0:0:0:0:0:8080] bound... 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 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 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] 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 +-------------------------------------------------+ | 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 |.... | +--------+-------------------------------------------------+----------------+ 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 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 +-------------------------------------------------+ | 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 |............ | +--------+-------------------------------------------------+----------------+ 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
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
- 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
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
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
4 解决方案
- 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
- 每一条消息采用固定长度，缺点浪费空间
- 每一条消息采用分隔符，例如 \n，缺点需要转义
- 每一条消息分为 head 和 body，head 中包含 body 的长度
4.1 方法1：短链接
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(); } } }
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
4.2：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
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
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
4.3 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); 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
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
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
4.4 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
// 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); // 先写入长度 buffer.writeByte(length); // 再 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
