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在 Python 2 和 3k中，当端口已被使用时 usingwsgi.simple_server.make_server(host, port, app)不会引发异常。相反，调用.server_forever()或.handle_request()只是阻塞，直到另一个端口关闭并且下一个连接传入。

import wsgiref.simple_server as simple_server

def application(environ, start_response):
    start_response('200 OK', [('Content-type', 'text/html')])
    return ["<html><body><p>Hello!</p></body></html>".encode('utf-8')]

def main():
    server = simple_server.make_server('', 8901, application)
    server.serve_forever()

if __name__ == "__main__":
    main()

我希望会引发异常，因为socket.socket.bind()在这种情况下也会引发异常。有没有办法确定返回的是否HTTPServer成功绑定到指定端口？

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1 回答 1

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我找到了这个原因。Python 2.7.8 中的HTTPServer类源代码如下：

class HTTPServer(SocketServer.TCPServer):

    allow_reuse_address = 1    # Seems to make sense in testing environment

    def server_bind(self):
        """Override server_bind to store the server name."""
        import pdb; pdb.set_trace()
        SocketServer.TCPServer.server_bind(self)
        host, port = self.socket.getsockname()[:2]
        self.server_name = socket.getfqdn(host)
        self.server_port = port

并像这样allow_reuse_address使用SocketServer.TCPServer.server_bind()：

class TCPServer(BaseServer):

    # ...

    def server_bind(self):
        """Called by constructor to bind the socket.

        May be overridden.

        """
        if self.allow_reuse_address:
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.socket.bind(self.server_address)
        self.server_address = self.socket.getsockname()

设置allow_reuse_address为False将导致self.socket.bind(self.server_address)引发异常。我想知道课堂上的这一行HTTPServer是否是故意的，因为评论说它“在测试环境中有意义”。

于 2014-08-09T16:46:55.070 回答