Python套接字：无效的起始字节

我正在使用 Python 套接字来接收文件。但是，有时我会收到以下错误：

Traceback (most recent call last):
  File "C:\Users\Sharkoon\Nextcloud\Elektronik\pythonProject\main.py", line 54, in receive_File
    received = client_socket.recv(BUFFER_SIZE).decode()
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x94 in position 34: invalid start byte

Process finished with exit code 1

这发生在代码的第 4 到第 9 次执行时。难道是我在文件完全发送之前尝试解码？

代码如下：

# device's IP address
SERVER_HOST = "0.0.0.0"
SERVER_PORT = 1337

# receive 4096 bytes each time
BUFFER_SIZE = 4096
SEPARATOR = "<SEPARATOR>"


def receive_File():
    # create the server socket
    # TCP socket
    s = socket.socket()
    # bind the socket to our local address
    s.bind((SERVER_HOST, SERVER_PORT))

    s.listen(5)
    print(f"[*] Listening as {SERVER_HOST}:{SERVER_PORT}")
    # accept connection if there is any
    client_socket, address = s.accept()
    # if below code is executed, that means the sender is connected
    print(f"[+] {address} is connected.")

    # receive the file infos
    # receive using client socket, not server socket
    received = client_socket.recv(BUFFER_SIZE).decode()
    filename, filesize = received.split(SEPARATOR)
    # remove absolute path if there is
    filename = os.path.basename(filename)
    # convert to integer
    filesize = int(filesize)

    # start receiving the file from the socket
    # and writing to the file stream
    progress = tqdm.tqdm(range(filesize), f"Receiving {filename}", unit="B", unit_scale=True, unit_divisor=1024)
    with open(filename, "wb") as f:
        while True:
            # read 1024 bytes from the socket (receive)
            bytes_read = client_socket.recv(BUFFER_SIZE)
            if not bytes_read:
                # nothing is received
                # file transmitting is done
                break
                # write to the file the bytes we just received
            f.write(bytes_read)
            # update the progress bar
            progress.update(len(bytes_read))


    # close the server socket
    s.close()
    return filename

我正在使用的代码来自这里：https://www.thepythoncode.com/article/send-receive-files-using-sockets-python https://www.thepythoncode.com/article/send-receive-files-using-sockets-python

未知服务器提供什么，但根据代码，您期望传输的数据是文件名、一些分隔符、文件大小，然后是实际数据。

received = client_socket.recv(BUFFER_SIZE).decode()
filename, filesize = received.split(SEPARATOR)

这里你假设单个recv将返回一个包含文件名、分隔符和文件大小的缓冲区。具体来说，您期望缓冲区将 a) 包含所有这些 and b) 只有这个。这可能来自于这样的假设：单个send服务器上的内容将与您的完全匹配recv在客户端中。

This 假设是错误的。 TCP是字节流，而不是消息协议。recv(BUFFER_SIZE)将返回最多 BUFFER_SIZE 字节。这可能低于预期数据，但也可能更多。

具体来说，它可能已经包含文件中的二进制数据，该数据无法解码为 utf-8 - 导致：

UnicodeDecodeError: 'utf-8' codec can't decode byte 0x94 in position 34: invalid start byte

要修复此问题，您需要知道 utf-8 编码的标头在哪里结束以及二进制数据在哪里开始。这可以通过在服务器中的标头前添加长度前缀或在文件大小和文件内容之间添加另一个分隔符来完成。