Netty自定义协议解析原理与应用

public class ServerManager {

   private int port;

   public ServerManager(int port) {

       this.port = port;

   }

   //参考的官方例子

   public void run() throws Exception {

       EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)

       EventLoopGroup workerGroup = new NioEventLoopGroup();

       try {

           ServerBootstrap b = new ServerBootstrap(); // (2)

           b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class) // (3)

           .childHandler(new ChannelInitializer<SocketChannel>() { // (4)

               @Override

               public void initChannel(SocketChannel ch) throws Exception {

                   //这里就是添加解码器的地方，它有几种不同的构造方法。下面是带全部参数的构造方法，这些参数的作用将在下面的例子中说明，这里没有赋值。ByteOrder可以选择编码是大端还是小端（关于大端或小端的问题，不明白的请自行百度），maxFrameLength表示接收到的包的最大长度。

                   ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(ByteOrder.BIG_ENDIAN, maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment, initialBytesToStrip, failFast));

                   ch.pipeline().addLast(new ServerHandler());

           }

       }).option(ChannelOption.SO_BACKLOG, 128) // (5)

       .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)

   // Bind and start to accept incoming connections.

   ChannelFuture f = b.bind(port).sync(); // (7)

   // Wait until the server socket is closed.

   // In this example, this does not happen, but you can do that to

   // gracefully

   // shut down your server.

   f.channel().closeFuture().sync();

   } finally {

       workerGroup.shutdownGracefully();

       bossGroup.shutdownGracefully();

       }

   }

}

lengthFieldLength   = 2

lengthAdjustment    = 0

initialBytesToStrip = 0 (= do not strip header)

BEFORE DECODE (14 bytes)         AFTER DECODE (14 bytes)

+--------+----------------+      +--------+----------------+

| Length | Actual Content |----->| Length | Actual Content |

| 0x000C | "HELLO, WORLD" |      | 0x000C | "HELLO, WORLD" |

+--------+----------------+      +--------+----------------+

public class ServerHandler implements ChannelInboundHandler {

public void handlerAdded(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void channelRegistered(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void channelActive(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void channelInactive(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

   ByteBuf byteBuf = (ByteBuf) msg;

   //读取包的包长度

   int len = byteBuf.readInt();

   //剩下的就是包内容了。

   .........

}

public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {

// TODO Auto-generated method stub

}

public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {

// TODO Auto-generated method stub

}

public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {

// TODO Auto-generated method stub

//cause.printStackTrace();

}