知识点前文请阅读：Netty入门
粘包、半包
服务器端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup boss = new NioEventLoopGroup();
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(boss, worker);
// 设置服务器端接收缓冲区大小为 10 字节
serverBootstrap.option(ChannelOption.SO_RCVBUF, 10);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
客户端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(worker);
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
// 向服务器端发送 5 次数据，每次 发送16个字节
for (int i = 0; i < 5; i++) {
ByteBuf buf = ctx.alloc().buffer(16);
buf.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
ctx.writeAndFlush(buf);
}
}
});
}
});
ChannelFuture channelFuture = bootstrap.connect(new InetSocketAddress("localhost", 8080)).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
worker.shutdownGracefully();
}
}
服务器端打印结果
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] REGISTERED
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] ACTIVE
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ: 36B // 可以看到这里接收到 36 字节，客户端每次发送 16 个字节，服务器端这里一次接收了36字节，36 > 16 出现了粘包现象，16:16:4 最后4这里出现了半包现象
+-------------------------------------------------+
| 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 |.... |
+--------+-------------------------------------------------+----------------+
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ COMPLETE
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ: 40B
+-------------------------------------------------+
| 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 |........ |
+--------+-------------------------------------------------+----------------+
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ COMPLETE
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ: 4B // 半包
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 0c 0d 0e 0f |.... |
+--------+-------------------------------------------------+----------------+
15:23:38 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x8fc90ea3, L:/127.0.0.1:8080 - R:/127.0.0.1:53151] READ COMPLETE
看 READ 类型，可以看到这里接收到 36 字节，客户端每次发送 16 个字节，服务器端这里一次接收了36字节，36 > 16 出现了粘包现象，16:16:4 最后4这里出现了半包现象
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，需要开发人员找出消息的边界
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
图中窗口内的4段(1-1000、1001-2000、2001-3000、3001-4000)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 1-1000 这个段的数据 ack 回来了，窗口就可以向前滑动，就可以发送 4001-5000 段的数据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
// 调整服务器端 滑动窗口大小，一般不用设置，在建立连接后系统自动设置，netty默认的是1024 serverBootstrap.option(ChannelOption.SO_RCVBUF, 10); // 调整客户端 滑动窗口大小，一般不用设置，在建立连接后系统自动设置，netty默认的是1024 bootstrap.option(ChannelOption.SO_SNDBUF, 10); // 调整 netty 的接收缓冲区大小（ByteBuf） AdaptiveRecvByteBufAllocator(最小值, 初始值, 最大值) serverBootstrap.childOption(ChannelOption.RCVBUF_ALLOCATOR, new AdaptiveRecvByteBufAllocator(16, 16, 16));
/ 插播知识点 /
option：全局配置
childOption：单个 channel 连接的配置
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(20) 头和 ip(20) 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
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
- 解决方案一：短链接
服务器端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup boss = new NioEventLoopGroup();
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(boss, worker);
// 设置服务器端接收缓冲区大小为 10 字节
// serverBootstrap.option(ChannelOption.SO_RCVBUF, 10);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
客户端
public static void main(String[] args) throws InterruptedException {
// 发送5次
for (int i = 0; i < 5; i++) {
send();
}
}
private static void send() {
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(worker);
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ByteBuf buf = ctx.alloc().buffer(16);
buf.writeBytes(new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15});
ctx.writeAndFlush(buf);
// 发送一次消息后，就关闭 channel 通道，关闭连接
ctx.channel().close();
}
});
}
});
ChannelFuture channelFuture = bootstrap.connect(new InetSocketAddress("localhost", 8080)).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
worker.shutdownGracefully();
}
}
服务器端打印
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 - R:/127.0.0.1:51412] REGISTERED
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 - R:/127.0.0.1:51412] ACTIVE
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 - R:/127.0.0.1:51412] READ: 16B
+-------------------------------------------------+
| 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 |................|
+--------+-------------------------------------------------+----------------+
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 - R:/127.0.0.1:51412] READ COMPLETE
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 - R:/127.0.0.1:51412] READ COMPLETE
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 ! R:/127.0.0.1:51412] INACTIVE
16:37:52 [DEBUG] [nioEventLoopGroup-3-8] i.n.h.l.LoggingHandler - [id: 0xffa06125, L:/127.0.0.1:8080 ! R:/127.0.0.1:51412] UNREGISTERED
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 - R:/127.0.0.1:51429] REGISTERED
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 - R:/127.0.0.1:51429] ACTIVE
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 - R:/127.0.0.1:51429] READ: 16B
+-------------------------------------------------+
| 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 |................|
+--------+-------------------------------------------------+----------------+
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 - R:/127.0.0.1:51429] READ COMPLETE
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 - R:/127.0.0.1:51429] READ COMPLETE
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 ! R:/127.0.0.1:51429] INACTIVE
16:37:52 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x3f21d899, L:/127.0.0.1:8080 ! R:/127.0.0.1:51429] UNREGISTERED
......
可以看到可以数据没有粘在一起了，解决了粘包问题
但是短链接不能解决半包问题
测试短链接半包现象代码改造，调整服务器端netty接收缓冲区大小为16个字节，netty最小16个字节，因为取16的倍数（serverBootstrap.childOption(ChannelOption.RCVBUF_ALLOCATOR, new AdaptiveRecvByteBufAllocator(16, 16, 16));）------- 客户端一次发送超过16个字节的数据即可。这里就不再重复贴相似的代码了
- 解决方案二：固定长度
FixedLengthframeDecoder：netty 提供的定长解码器，构造方法参数：和客户端约定传递消息的长度
服务器端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup boss = new NioEventLoopGroup();
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(boss, worker);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
// FixedLengthframeDecoder：netty 提供的定长解码器，构造方法参数：和客户端约定传递消息的长度
ch.pipeline().addLast(new FixedLengthframeDecoder(10));
ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
客户端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(worker);
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ByteBuf buf = ctx.alloc().buffer();
char c = '0';
for (int i = 0; i < 5; i++) {
byte[] bytes = fill10Bytes(c, new Random().nextInt(10) + 1);
c++;
buf.writeBytes(bytes);
}
ctx.writeAndFlush(buf);
}
});
}
});
ChannelFuture channelFuture = bootstrap.connect(new InetSocketAddress("localhost", 8080)).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
worker.shutdownGracefully();
}
}
public static byte[] fill10Bytes(char c, int len) {
byte[] bytes = new byte[10];
Arrays.fill(bytes, (byte) '_');
for (int i = 0; i < len; i++) {
bytes[i] = (byte) c;
}
System.out.println(new String(bytes));
return bytes;
}
服务器端打印
17:22:44 [DEBUG] [nioEventLoopGroup-3-3] i.n.h.l.LoggingHandler - [id: 0x565dcfb4, L:/127.0.0.1:8080 - R:/127.0.0.1:53524] REGISTERED
17:22:44 [DEBUG] [nioEventLoopGroup-3-3] i.n.h.l.LoggingHandler - [id: 0x565dcfb4, L:/127.0.0.1:8080 - R:/127.0.0.1:53524] ACTIVE
17:22:44 [DEBUG] [nioEventLoopGroup-3-3] i.n.h.l.LoggingHandler - [id: 0x565dcfb4, L:/127.0.0.1:8080 - R:/127.0.0.1:53524] READ: 10B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 30 30 30 30 30 30 30 5f 5f 5f |0000000___ |
+--------+-------------------------------------------------+----------------+
17:22:44 [DEBUG] [nioEventLoopGroup-3-3] i.n.h.l.LoggingHandler - [id: 0x565dcfb4, L:/127.0.0.1:8080 - R:/127.0.0.1:53524] READ: 10B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 31 31 31 5f 5f 5f 5f 5f 5f 5f |111_______ |
+--------+-------------------------------------------------+----------------+
17:22:44 [DEBUG] [nioEventLoopGroup-3-3] i.n.h.l.LoggingHandler - [id: 0x565dcfb4, L:/127.0.0.1:8080 - R:/127.0.0.1:53524] READ: 10B
......
- 解决方案三：分隔符
LinebasedframeDecoder：netty 提供的支持 n 和 rn 符号的解码器，构造参数传遇到换行符的最大长度，当读了指定长度的字节时，还没有遇到换行符，将抛出异常DelimiterbasedframeDecoder：netty 提供的支持 自定义符号的解码器，构造参数传符号的最大长度，和ByteBuf类型的自定义符号
服务器端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup boss = new NioEventLoopGroup();
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(boss, worker);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
// ch.pipeline().addLast(new LinebasedframeDecoder(1024));
ch.pipeline().addLast(new DelimiterbasedframeDecoder(1024, ByteBufAllocator.DEFAULT.buffer().writeBytes("|".getBytes(StandardCharsets.UTF_8))));
ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
客户端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(worker);
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ByteBuf buf = ctx.alloc().buffer();
//buf.writeBytes("hellonworldnhinzhang sann".getBytes(StandardCharsets.UTF_8));
buf.writeBytes("hello|world|hi|zhang san|".getBytes(StandardCharsets.UTF_8));
ctx.writeAndFlush(buf);
}
});
}
});
ChannelFuture channelFuture = bootstrap.connect(new InetSocketAddress("localhost", 8080)).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
worker.shutdownGracefully();
}
}
服务器端打印
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] REGISTERED
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] ACTIVE
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] READ: 5B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 65 6c 6c 6f |hello |
+--------+-------------------------------------------------+----------------+
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] READ: 5B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 77 6f 72 6c 64 |world |
+--------+-------------------------------------------------+----------------+
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] READ: 2B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 69 |hi |
+--------+-------------------------------------------------+----------------+
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] READ: 9B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 7a 68 61 6e 67 20 73 61 6e |zhang san |
+--------+-------------------------------------------------+----------------+
17:44:53 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x4cd3ff09, L:/127.0.0.1:8080 - R:/127.0.0.1:53948] READ COMPLETE
- 解决方案四：预设长度 LTC解码器
LengthFieldbasedframeDecoder：构造参数传(最大长度，记录长度偏移量，长度占用字节数，长度调整，剥离字节数)
服务器端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup boss = new NioEventLoopGroup();
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(boss, worker);
serverBootstrap.channel(NioServerSocketChannel.class);
serverBootstrap.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
// 参数一：最大字节数，
// 参数二：长度在buf中的偏移量，因为我在buf中先写的是长度，所以长度的偏移量是0，如果先写入2个字节的数据，再写入长度，那么长度的偏移量就是2
// 参数三：长度占用的字节，我写的是一个int类型，占用4个字节
// 参数四：需要调整的长度
// 参数五：数据从头开始需要剥离的长度，现在buf中的数据是 ....hello, world 和 ....hi!，前面的4个点是长度，我们不需要长度，所以需要把长度剥离出去
ch.pipeline().addLast(new LengthFieldbasedframeDecoder(1024, 0, 4, 0, 4));
ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
}
});
ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}
客户端
public static void main(String[] args) throws InterruptedException {
NioEventLoopGroup worker = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(worker);
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ChannelInitializer() {
@Override
protected void initChannel(NioSocketChannel ch) throws Exception {
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ByteBuf buf = ctx.alloc().buffer();
msg(buf, "hello, world");
msg(buf, "hi!");
ctx.writeAndFlush(buf);
}
});
}
});
ChannelFuture channelFuture = bootstrap.connect(new InetSocketAddress("localhost", 8080)).sync();
channelFuture.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
worker.shutdownGracefully();
}
}
private static void msg(ByteBuf buf, String content) {
byte[] bytes = content.getBytes(StandardCharsets.UTF_8); // 实际内容
int length = bytes.length; // 实际内容长度
buf.writeInt(length); // int的长度是4个字节，把长度写入
buf.writeBytes(bytes);
}
服务器端打印
18:36:43 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x21c2c017, L:/127.0.0.1:8080 - R:/127.0.0.1:59190] REGISTERED
18:36:43 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x21c2c017, L:/127.0.0.1:8080 - R:/127.0.0.1:59190] ACTIVE
18:36:43 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x21c2c017, L:/127.0.0.1:8080 - R:/127.0.0.1:59190] READ: 12B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 |hello, world |
+--------+-------------------------------------------------+----------------+
18:36:43 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x21c2c017, L:/127.0.0.1:8080 - R:/127.0.0.1:59190] READ: 3B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 69 21 |hi! |
+--------+-------------------------------------------------+----------------+
18:36:43 [DEBUG] [nioEventLoopGroup-3-1] i.n.h.l.LoggingHandler - [id: 0x21c2c017, L:/127.0.0.1:8080 - R:/127.0.0.1:59190] READ COMPLETE
加深 LengthFieldbasedframeDecoder 解码器的理解，使用 EmbeddedChannel 工具类调试
public static void main(String[] args) {
EmbeddedChannel embeddedChannel = new EmbeddedChannel(
// 参数一：最大字节数，
// 参数二：长度在buf中的偏移量，因为我在buf中先写的是长度，所以长度的偏移量是0，如果先写入2个字节的数据，再写入长度，那么长度的偏移量就是2
// 参数三：长度占用的字节，我写的是一个int类型，占用4个字节
// 参数四：需要调整的长度，现在除了内容以外，在buf中又加了1个字节长度的版本号，所以需要调整的长度是1
// 参数五：数据从头开始需要剥离的长度，现在buf中的数据是 .....hello, world 和 .....hi!，前面的4个点是长度，第5个点是版本号，我们不需要长度，所以需要把长度剥离出去，最后的数据是 .hello, world 和 .hi!
new LengthFieldbasedframeDecoder(1024, 0, 4, 1, 4)
, new LoggingHandler(LogLevel.DEBUG)
);
// 4 个字节的长度，然后是实际内容
ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
msg(buf, "hello, world");
msg(buf, "hi!");
embeddedChannel.writeInbound(buf);
}
private static void msg(ByteBuf buf, String content) {
byte[] bytes = content.getBytes(StandardCharsets.UTF_8); // 实际内容
int length = bytes.length; // 实际内容长度
// buf.writeBytes(new byte[]{1,2}); // 加入在长度之前多写入了两个字节的数据，那么LengthFieldbasedframeDecoder的第二个参数就是2
buf.writeInt(length); // int的长度是4个字节，把长度写入
buf.writeByte(1); // 传入其他数据，例如版本号
buf.writeBytes(bytes);
}
打印
18:50:42 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] REGISTERED
18:50:42 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] ACTIVE
18:50:42 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] READ: 13B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 01 68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 |.hello, world |
+--------+-------------------------------------------------+----------------+
18:50:42 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] READ: 4B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 01 68 69 21 |.hi! |
+--------+-------------------------------------------------+----------------+
18:50:42 [DEBUG] [main] i.n.h.l.LoggingHandler - [id: 0xembedded, L:embedded - R:embedded] READ COMPLETE
