使用扭曲控制传入字节的馈送

Question

我需要解决以下问题

作为连接到服务器的客户端，服务器以以下形式发送数据块：

[4 bytes][msg - block of bytes the size of int(previous 4 bytes)]

使用 twisted 时，我需要使用 msg 部分调用 dataReceived(self, data)，我不介意接收 4 字节前缀，但我需要以确保我一次获得整个消息块，而不是碎片化。

请指教。

Answer 1

我最终编写了以下自定义接收器

HEADER_LENGTH = 4

class CustomReceiver(Protocol):
    _buffer = b''

def dataReceived(self, data):
    logger.info(f'DATA RECEIVED: {data}')

    data = (self._buffer + data)
    header = data[:HEADER_LENGTH]
    logger.info(f'header: {header}   len: {len(header)}')
    while len(header) == HEADER_LENGTH:
        response_length = int.from_bytes(header, byteorder='big')
        response = data[HEADER_LENGTH:][:response_length]
        self.responseReceived(response)
        data = data[HEADER_LENGTH + response_length:]
        header = data[:HEADER_LENGTH]

    self._buffer = header

我不确定是否应该为 dataReceived() 添加锁定机制，同时调用会破坏 _buffer 数据。

Answer 2

StatefulProtocol 对这样的协议很有帮助。

from twisted.protocols.stateful import StatefulProtocol

HEADER_LENGTH = 4

class YourProtocol(StatefulProtocol):

    # Define the first handler and what data it expects.
    def getInitialState(self):
        return (
            # The first handler is self._header
            self._header, 
            # And it expects HEADER_LENGTH (4) bytes
            HEADER_LENGTH,
        )

    # When HEADER_LENGTH bytes have been received, this is called.
    def _header(self, data):
        # It returns a tuple representing the next state handler.
        return (
            # The next thing we can handle is a response
            self._response, 
            # And the response is made up of this many bytes.
            int.from_bytes(header, byteorder='big'),
        )

    # When the number of bytes from the header has been received,
    # this is called.
    def _response(self, data):
        # Application dispatch of the data
        self.responseReceived(data)
        # Return to the initial state to process the next received data.
        return self.getInitialState()

使用扭曲控制传入字节的馈送

Controlling the feed of incoming bytes using twisted

python

twisted