WinError 10061 - 无法建立连接

我正在调试一个过去有效的简单程序.我已经挑出了发生错误的指令,但我无法弄清楚是什么触发它.我已经阅读了与WinError 10061相关的所有问题,但我没有看到明确的答案

urllib.request.urlopen('http://www.wikipedia.org/')
Traceback (most recent call last):
File "C:\Python33\lib\urllib\request.py", line 1248, in do_open    h.request(req.get_method(), req.selector, req.data, headers)
File "C:\Python33\lib\http\client.py", line 1061, in request    self._send_request(method, url, body, headers)
File "C:\Python33\lib\http\client.py", line 1099, in _send_request    self.endheaders(body)
File "C:\Python33\lib\http\client.py", line 1057, in endheaders  self._send_output(message_body)
File "C:\Python33\lib\http\client.py", line 902, in _send_output    self.send(msg)
File "C:\Python33\lib\http\client.py", line 840, in send    self.connect()
File "C:\Python33\lib\http\client.py", line 818, in connect    self.timeout, self.source_address)
File "C:\Python33\lib\socket.py", line 435, in create_connection    raise err
File "C:\Python33\lib\socket.py", line 426, in create_connection    sock.connect(sa)
ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it

During handling of the above exception, another exception occurred: 

Traceback (most recent call last):
File "", line 1, in 
urllib.request.urlopen('http://www.wikipedia.org/')
File "C:\Python33\lib\urllib\request.py", line 156, in urlopen   return opener.open(url, data, timeout)
File "C:\Python33\lib\urllib\request.py", line 469, in open    response = self._open(req, data)
File "C:\Python33\lib\urllib\request.py", line 487, in _open    '_open', req)
File "C:\Python33\lib\urllib\request.py", line 447, in _call_chain    result = func(*args)
File "C:\Python33\lib\urllib\request.py", line 1268, in http_open    return self.do_open(http.client.HTTPConnection, req)
File "C:\Python33\lib\urllib\request.py", line 1251, in do_open    raise URLError(err)
urllib.error.URLError: 

我在Windows 8中运行Python 3.我试图关闭防火墙,正如几个人所说,但没有任何改变.我还尝试将Python添加到防火墙允许的应用程序列表中.顺便说一下,几天前,当我从我的电脑上删除了一些应用程序时,程序行没有任何问题.