Question

When running the following Java code, I get very accurate and consistent results in determining if the web page I’m testing is up.

protected synchronized boolean checkUrl(HttpURLConnection connection){     boolean error = false;     //HttpURLConnection connection = null;     GregorianCalendar calendar = new GregorianCalendar();      try{         if(connection != null){             connection.connect();              //200 is the expected HTTP_OK response             error = processResponseCode(connection.getResponseCode());              connection.disconnect();         } else{             error = false;         }      }catch(java.net.UnknownHostException uhe){         ...     }      catch(Exception e){         ...     }      return error; } 

The closest match to the Java pattern in c# has much higher results of false positives (mostly due to timeouts – which has a default period of 100000ms).

protected bool connectedToUrl = false;         response = null;          HttpWebRequest webreq = (HttpWebRequest)WebRequest.Create(this.getUri());         webreq.Credentials = CredentialCache.DefaultCredentials;         WebResponse res = null;// webreq.GetResponse();          try         {             WebRequest request = WebRequest.Create(this.getUri()) as WebRequest;             request.Credentials = CredentialCache.DefaultCredentials;              if (request != null)             {                 // Get response                  res = webreq.GetResponse();                  connectedToUrl = processResponseCode(res);             }             else             {                 logger.Fatal(getFatalMessage());                  string error = string.Empty;             }         }         catch (Exception e)         {             throw e;         }          return connectedToUrl;     } 

I have tried various patterns in c# to match the effectiveness of the quoted Java code, to no avail.

Any ideas?

Answer 1

Simply change this:

res = webreq.GetResponse(); connectedToUrl = processResponseCode(res); 

to

using (WebResponse res = webreq.GetResponse())  {     connectedToUrl = processResponseCode(res); } 

(Remove the declaration from earlier.)

Until you haven’t closed/disposed the response (or it’s been finalized), it’s holding onto the connection. You can only have a certain number (2 by default, I believe) of connections to any one host at a time, hence the timeouts. When you dispose the response, it allows another request to use the same connection.