HttpWebRequest Timeout

随着REST风格的流行，直接通过 HttpWebRequest 进行服务调用的客户端应用越来越多。这里总结一些可能需要费时调查的经验，希望能帮助大家。 

1. 用完的HttpWebRequest要Abort()或者要把 Response.Close() 
否则会导致请求Timeout。 (HttpWebRequest.Method默认是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);  

    }  

}  

上面的代码，会从第3次Request开始出现Timeout，因为GetResponse 后 Stream打开未关闭。 
 

解决方法：上面的代码中加上 resp.Close(); 或者 webReq.Abort(); 就能解决。 

2. 多线程中调用 HttpWebRequest 时，需要设置 ServicePointManager.DefaultConnectionLimit 数(默认连接数是 2)。 
当多线程请求时，同时的连接数超过Limit时，GetResponse会抛出 Timeout WebException。

 

// 用多线程同时发出4个请求   

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/" );  

解决方法：在GetResponse()之前设置 ServicePointManager.DefaultConnectionLimit = 100; 

3.  当请求一个基于SSL的服务时，默认的验证行为都在 ServicePointManager 定义： 
ServicePointManager.CheckCertificateRevocationList = true;

如果请求的服务端证书没有第三方的认证支持，则请求会失败，如果要完全信任服务端证书，则可以将 
CheckCertificateRevocationList  设为 false。 

4. 可以在 <system.net> 配置节中配置 HttpWebRequest 的属性，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> 

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

1. 用完的HttpWebRequest要Abort()或者要把 Response.Close() 
否则会导致请求Timeout。 (HttpWebRequest.Method默认是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);  

    }  

}  

上面的代码，会从第3次Request开始出现Timeout，因为GetResponse 后 Stream打开未关闭。 
 

解决方法：上面的代码中加上 resp.Close(); 或者 webReq.Abort(); 就能解决。 

2. 多线程中调用 HttpWebRequest 时，需要设置 ServicePointManager.DefaultConnectionLimit 数(默认连接数是 2)。 
当多线程请求时，同时的连接数超过Limit时，GetResponse会抛出 Timeout WebException。

 

// 用多线程同时发出4个请求   

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/" );  

解决方法：在GetResponse()之前设置 ServicePointManager.DefaultConnectionLimit = 100; 

3.  当请求一个基于SSL的服务时，默认的验证行为都在 ServicePointManager 定义： 
ServicePointManager.CheckCertificateRevocationList = true;

如果请求的服务端证书没有第三方的认证支持，则请求会失败，如果要完全信任服务端证书，则可以将 
CheckCertificateRevocationList  设为 false。 

4. 可以在 <system.net> 配置节中配置 HttpWebRequest 的属性，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> 

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