c# - HttpWebRequest times out on second call

Question

Why does the following code Timeout the second (and subsequent) time it is run?

The code hangs at:

using (Stream objStream = request.GetResponse().GetResponseStream())

and then causes a WebException saying that the request has timed out.

I have tried this with a WebRequest and HttpWebRequest

Edit: It seems the code is falling over in request.GetResponse()

Edit: This post suggests it may be a GC issue --> http://www.vbforums.com/showthread.php?t=610043 - as per this post the issue is mitigated if Fiddler is open in the background.

The server is there and available for requests.

    private string GetQLMResponse(string URL)
    {
        HttpWebRequest request = WebRequest.Create(URL) as HttpWebRequest;
        request.Credentials = new NetworkCredential(Settings.Default.LicenseUser, Settings.Default.LicensePassword);
        request.KeepAlive = false;
        request.Timeout = 5000;
        request.Proxy = null;

        // Read stream
        string responseString = String.Empty;
        try
        {
            using (var response = request.GetResponse())
            {
                using (Stream objStream = response.GetResponseStream())
                {
                    using (StreamReader objReader = new StreamReader(objStream))
                    {
                        responseString = objReader.ReadToEnd();
                        objReader.Close();
                    }
                    objStream.Flush();
                    objStream.Close();
                }
                response.Close();
            }
        }
        catch (WebException ex)
        {
            throw new LicenseServerUnavailableException();
        }
        finally
        {
            request.Abort();
            request = null;
            GC.Collect();
        }
        return responseString;
    }

Thrown WebException is:

{"The operation has timed out"} [System.Net.WebException]: {"The operation has timed out"} Data: {System.Collections.ListDictionaryInternal} HelpLink: null InnerException: null Message: "The operation has timed out" Source: "System" StackTrace: " at System.Net.HttpWebRequest.GetResponse() at IQX.Licensing.License.GetQLMResponse(String URL) in C:UsersjdSVNjdProductsDevelopmentJAD.LicensingJAD.LicensingLicense.cs:line 373" TargetSite: {System.Net.WebResponse GetResponse()}

---

Update: OK So the following code now works. The servicePoint was setting the timeout to be near 4 minutes. Changing ServicePoint.ConnectionLeaseTimeout on the request object means that the request is now destroyed after 5000ms. Thanks to all for your help and also to these 2 pages:

1. http://blogs.msdn.com/b/adarshk/archive/2005/01/02/345411.aspx

2. http://msdn.microsoft.com/en-us/library/6hszazfz(v=VS.80).aspx

   private string GetQLMResponse(string URL)
   {
       HttpWebRequest request = WebRequest.Create(URL) as HttpWebRequest;
       request.Credentials = new NetworkCredential(Settings.Default.LicenseUser, Settings.Default.LicensePassword);
       request.KeepAlive = false;
       request.Timeout = 5000;
       request.Proxy = null;
   
       request.ServicePoint.ConnectionLeaseTimeout = 5000;
       request.ServicePoint.MaxIdleTime = 5000;
   
       // Read stream
       string responseString = String.Empty;
       try
       {
           using (WebResponse response = request.GetResponse())
           {
               using (Stream objStream = response.GetResponseStream())
               {
                   using (StreamReader objReader = new StreamReader(objStream))
                   {
                       responseString = objReader.ReadToEnd();
                       objReader.Close();
                   }
                   objStream.Flush();
                   objStream.Close();
               }
               response.Close();
           }
       }
       catch (WebException ex)
       {
           throw new LicenseServerUnavailableException();
       }
       finally
       {
           request.Abort();
       }
       return responseString;
   }
   

Answer 1

On the heels of the previous answers, I wanted to add a couple more things. By default HttpWebRequest allows only 2 connections to the same host (this is HTTP 1.1 "niceness"),

Yes, it can be overriden, no I won't tell you how in this question, you have to ask another one :) I think you ought to look at this post.

I think that you are still not quite disposing of all your resources connected with the HttpWebRequest, so the connection pooling comes into play and that's the problem. I wouldn't try to fight the 2 connections per server rule, unless you really have to.

As one of the posters above noted, Fiddler is doing you a bit of a disservice in this case.

I'd add a nice finally {} clause after your catch and make sure that as the above post notes, all streams are flushed, closed and references to the request object are set to null.

Please let us know if this helps.