HttpWebRequest Timeout

1. 用完的HttpWebRequest要Abort()或者要把 Response.Close() 
否則會導致請求Timeout。 (HttpWebRequest.Method默認是GET)

 

static   void  Main( string [] args)  

{  

for  ( int  i = 0; i < 10; i++)  

    {  

        Console.Write( "[{0}] Request - " , i + 1);  

        TryGet( "https://login.live.com/" );  

    }  

    Console.Read();  

}  

static   void  TryGet( object  obj)  

{  

try   

    {  

        HttpWebRequest webReq =  null ;  

string  url = ( string )obj;  

        webReq = (HttpWebRequest)HttpWebRequest.Create(url);  

        webReq.Timeout = 20 * 1000;  

        var resp = webReq.GetResponse()  as  HttpWebResponse;  

        resp.Close();  

        Console.WriteLine( "Get Response StatusCode: {0}({1})" ,   

            resp.StatusCode, ( int )resp.StatusCode);  

    }  

catch  (WebException we)  

    {  

        Console.WriteLine( "Get Response StatusCode: {0}({1})" ,  

            we.Status, ( int )we.Status);  

    }  

catch  (Exception ex)  

    {  

        Console.WriteLine(ex);  

    }  

}  

 

上面的代碼，會從第3次Request開始出現Timeout，因為GetResponse 后 Stream打開未關閉。 
 

解決方法：上面的代碼中加上 resp.Close(); 或者 webReq.Abort(); 就能解決。 

2. 多線程中調用 HttpWebRequest 時，需要設置 ServicePointManager.DefaultConnectionLimit 數(默認連接數是 2)。 
當多線程請求時，同時的連接數超過Limit時，GetResponse會拋出 Timeout WebException。

 

// 用多線程同時發出4個請求   

WaitCallback methodTarget =  new  WaitCallback(TryGet);  

ThreadPool.QueueUserWorkItem(methodTarget,  "https://login.live.com/" );  

ThreadPool.QueueUserWorkItem(methodTarget,  "https://login.live.com/" );  

ThreadPool.QueueUserWorkItem(methodTarget,  "https://login.live.com/" );  

ThreadPool.QueueUserWorkItem(methodTarget,  "https://login.live.com/" );  

 

 

 

解決方法：在GetResponse()之前設置 ServicePointManager.DefaultConnectionLimit = 100; 

3.  當請求一個基於SSL的服務時，默認的驗證行為都在 ServicePointManager 定義： 
ServicePointManager.CheckCertificateRevocationList = true;

如果請求的服務端證書沒有第三方的認證支持，則請求會失敗，如果要完全信任服務端證書，則可以將 
CheckCertificateRevocationList  設為 false。 

4. 可以在 <system.net> 配置節中配置 HttpWebRequest 的屬性，包括 WebProxy

 

<system.net>    
  <connectionManagement>    

  </connectionManagement>   

  <defaultProxy>    

    <proxy proxyaddress= "http://xxx.xxx.xxx.xxx:xxx"  bypassonlocal= "False" />    

  </defaultProxy>   

  <settings>    

      <httpWebRequest useUnsafeHeaderParsing= "true" />   

      <servicePointManager checkCertificateName= "true"      

                           checkCertificateRevocationList= "true"       

                           enableDnsRoundRobin= "true"      

                           expect100Continue= "true"        

                           useNagleAlgorithm= "true" />      

  </settings>   

</system.net> 

 

原文鏈接：https://www.cnblogs.com/1971ruru/archive/2012/04/11/2442589.html?tdsourcetag=s_pctim_aiomsg#