用 HttpWebResponse 抓取页面时链接主机失败，这种情况是偶然发生，网站自己用的按说并发性不会很高，有没有大侠知道什么原因嘛？
抓取代码：
HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse httpResponse = (HttpWebResponse)httpRequest.GetResponse();
StreamReader sr = new StreamReader(httpResponse.GetResponseStream(), Encoding.UTF8);
String str = sr.ReadToEnd();
String appPath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase.TrimEnd(Path.DirectorySeparatorChar);
sr.Close();
英文原文报错 ：
System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
下面是翻译过来的：
System.Net.Sockets。SocketException:连接尝试失败，因为被连接方在一段时间后没有正确响应，或者建立的连接失败，因为连接的主机没有响应
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/4741/viewspace-3124634/ ，如需转载，请注明出处，否则将追究法律责任。
