pyspider error 599

Question

HTTP 599: Empty reply from server
[E 160201 11:28:39 base_handler:195] HTTP 599: Empty reply from server
    Traceback (most recent call last):
      File "/usr/lib/python2.6/site-packages/pyspider-0.3.7-py2.6.egg/pyspider/libs/base_handler.py", line 188, in run_task
        result = self._run_task(task, response)
      File "/usr/lib/python2.6/site-packages/pyspider-0.3.7-py2.6.egg/pyspider/libs/base_handler.py", line 167, in _run_task
        response.raise_for_status()
      File "/usr/lib/python2.6/site-packages/pyspider-0.3.7-py2.6.egg/pyspider/libs/response.py", line 190, in raise_for_status
        raise http_error
    HTTPError: HTTP 599: Empty reply from server

如题，这个599到底是啥原因，换了台机器，同样的爬虫就没问题，但是这机器的网速是有10多M/s，求教啊。