问

Netty客户端是否仅使用netty服务器？

 纤妍内衣天旺店 发布于 2022-12-08 16:27
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    • 我正在尝试开发一个客户端,使用自定义协议与生物识别设备进行通信,但似乎没有任何效果.我正在使用MessageToByteEncoder和MessageToByteDecoder来处理输入和输出数据:

    public class PacketDecoder extends ByteToMessageDecoder {
    @Override
    protected void decode(ChannelHandlerContext context, ByteBuf input, List out) throws Exception {
        System.out.println("readable bytes: " + input.readableBytes());
        if (input.readableBytes() >= 1) {
            if (input.getByte(0) != DataCodes.START_BYTE) {
                input.readByte();
                return;
            }
        }
        if (input.readableBytes() >= 3) {
            byte command = input.getByte(2);
            boolean extendedLenght = (command & 0x80) == 0x80;
            short dataLength;
            int headerLength;
            if (extendedLenght) {
                byte[] dataLengthBytes = new byte[2];
                input.getBytes(3, dataLengthBytes);
                dataLength = Utils.getShort(dataLengthBytes);
                headerLength = 5;
            } else {
                dataLength = input.getByte(3);
                headerLength = 4;
            }

            int totalLength = headerLength + dataLength + 16;
            if (input.readableBytes() >= totalLength) {
               byte[] packetBytes = input.readBytes(totalLength).array();
                Packet packet = PacketConverter.decode(packetBytes);
                System.out.println("packet decoded");
                out.add(packet);
            }
        }
    }
}


public class PacketEncoder extends MessageToByteEncoder {
    @Override
    protected void encode(ChannelHandlerContext context, Packet packet, ByteBuf out) throws Exception {
        byte[] packetBytes = PacketConverter.encode(packet);
        out.writeBytes(packetBytes);
    }
}



    和连接类:
    


    public class Connection implements PacketListener {
    private final byte deviceAddress;
    private ChannelFuture channelFuture;
    private EventLoopGroup workerGroup;
    private final Object readLock = new Object();
    private Packet responsePacket;

    public Connection(byte deviceAddress) {
        this.deviceAddress = deviceAddress;
    }

    public void connect(String address, int port) {
        workerGroup = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(workerGroup);
        b.channel(NioSocketChannel.class);
        b.option(ChannelOption.SO_KEEPALIVE, true);
        b.handler(new ChannelInitializer() {
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
                socketChannel.pipeline().addLast(
                        new PacketEncoder(),
                        new PacketDecoder(),
                        new PacketHandler(Connection.this)
                );
            }
        });

        channelFuture = b.connect(address, port);
    }

    public void disconnect() {
        channelFuture.channel().disconnect().syncUninterruptibly();
        workerGroup.shutdownGracefully();
    }

    @Override
    public void receive(Packet packet) {
        synchronized (readLock) {
            this.responsePacket = packet;
            readLock.notify();
        }
    }

    public Response send(Command command, int responseTimeout) throws TimeOutException {
        Packet packet = new Packet();
        packet.setCommand(command.getCommandCode());
        packet.setData(command.getCommandData());
        packet.setAddress(deviceAddress);

        synchronized (readLock) {
            responsePacket = null;
            channelFuture.channel().writeAndFlush(packet).syncUninterruptibly();
            try {
                readLock.wait(responseTimeout);
            } catch (InterruptedException e) {
            }
            if (responsePacket == null)
                throw new TimeOutException();
            return Response.get(responsePacket);
        }
    }
}

    


    在解码器上,它带有0个可读字符,我不确定enconder是否正在发送任何数据.我唯一的猜测是服务器需要是一个Netty实现.
            
        
        
    

        
    
        
    1 个回答
    
        
      
                        
    • 
                
      
  
      Netty客户端是否仅使用netty服务器？
      

      


      不会.一般来说,Netty提供网络抽象和事件循环结构,以减轻滚动自己的痛苦和陷阱.
      


      虽然您的示例相对简单,但我建议您根据工作示例构建代码,然后在更有意义的情况下添加功能/结构.例如,查看echo示例.尝试使用这种结构,不要担心获得干净的类层次结构(同步,超时等),直到你可以发送/接收一些字节.
      


      使用ByteBuf界面时一般要小心.您的input.getByte(..)呼叫使用绝对索引,而不是基于readerIndex()可能导致超出范围异常的索引.请参考ByteBuf javadocs,但您可能只想坚持readByte()或至少使用readerIndex().
      


      其他一般疑难解答问题:
      


      1)您是否确认您正在发送正确的信息并且设备正在接收它？
      


      2)您是否已验证设备是否响应了预期的响应？
      
        
      
                
      
                    
      2022-12-11 02:55  回答
      
                    
                
      
            
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