Python socket实现ftp下载空TXT文件显示网络错误

Question

问题相关代码，请勿粘贴截图

        ftp.connect('10.2.11', 21)
         ftp.login('yy', 'yy')
        bufsize = 1024
        from io import BytesIO
        cache_file = BytesIO()
        ftp.retrbinary('RETR ' + url, cache_file.write, bufsize)

        response = HttpResponse(content_type='application/octet-stream')
        response.write(cache_file.getvalue())
        cache_file.close()
        return response

  def  retrbinary(self, cmd, callback, blocksize=8192, rest=None):
        self.voidcmd('TYPE I')
        with self.transfercmd(cmd, rest) as conn:
        while 1:
            data = conn.recv(blocksize)
            callback(data)
            if not data:
                break
        # shutdown ssl layer
        if _SSLSocket is not None and isinstance(conn, _SSLSocket):
            conn.unwrap()
      return self.voidresp()

  def transfercmd(self, cmd, rest=None):
        return self.ntransfercmd(cmd, rest)[0]

  def ntransfercmd(self, cmd, rest=None):
    size = None
    if self.passiveserver:
        host, port = self.makepasv()
        conn = socket.create_connection((host, port), self.timeout,
                                        source_address=self.source_address)
        try:
            if rest is not None:
                self.sendcmd("REST %s" % rest)
            resp = self.sendcmd(cmd)

            if resp[0] == '2':
                resp = self.getresp()
            if resp[0] != '1':
                raise error_reply(resp)
        except:
            conn.close()
            raise
    else:
        with self.makeport() as sock:
            if rest is not None:
                self.sendcmd("REST %s" % rest)
            resp = self.sendcmd(cmd)
            # See above.
            if resp[0] == '2':
                resp = self.getresp()
            if resp[0] != '1':
                raise error_reply(resp)
            conn, sockaddr = sock.accept()
            if self.timeout is not _GLOBAL_DEFAULT_TIMEOUT:
                conn.settimeout(self.timeout)
    if resp[:3] == '150':
        # this is conditional in case we received a 125
        size = parse150(resp)
    return conn, size

运行结果及报错内容

pycharm运行无报错，部署后下载显示网络错误

我想要达到的结果

可以正常下载空txt文件