def start(self):
  """
  Starts the Service.
  :Exceptions:
   - WebDriverException : Raised either when it can't start the service
   or when it can't connect to the service
  """
  try:
   cmd = [self.path]
   cmd.extend(self.command_line_args())
   if 'win32' in str(sys.platform).lower(): ### 这里判断是否是windows平台
    ### 在windows平台上就隐藏窗口
    startupinfo = subprocess.STARTUPINFO()
    startupinfo.dwFlags = subprocess.CREATE_NEW_CONSOLE | subprocess.STARTF_USESHOWWINDOW
    startupinfo.wShowWindow = subprocess.SW_HIDE
   else:
    startupinfo = None
   self.process = subprocess.Popen(cmd, env=self.env,
           close_fds=platform.system() != 'Windows',
           stdout=self.log_file, stderr=self.log_file,startupinfo=startupinfo) ### 启动驱动
   self.PID = self.process.pid ### 将cmd窗口的进程pid 保留 因为 窗口被隐藏了 所以在后续程序中必须考虑主控进程结束的时候必须结束掉 驱动cmd窗口进程
  except TypeError:
   raise
  except OSError as err:
   if err.errno == errno.ENOENT:
    raise WebDriverException(
     "'%s' executable needs to be in PATH. %s" % (
      os.path.basename(self.path), self.start_error_message)
    )
   elif err.errno == errno.EACCES:
    raise WebDriverException(
     "'%s' executable may have wrong permissions. %s" % (
      os.path.basename(self.path), self.start_error_message)
    )
   else:
    raise
  except Exception as e:
   raise WebDriverException(
    "The executable %s needs to be available in the path. %s\n%s" %
    (os.path.basename(self.path), self.start_error_message, str(e)))
  count = 0
  while True:
   self.assert_process_still_running()
   if self.is_connectable():
    break
   count += 1
   time.sleep(1)
   if count == 30:
    raise WebDriverException("Can not connect to the Service %s" % self.path)