Throwing a WebException while posting XML data using HttpWebRequest and HttpWebrequest in c# -

i trying response xml uidai data centers sending xml document using httpwebrequest , receiving using httpwebresponse in c#asp.net web based application. checked using java application , working fine on side web based application throwing exception

an exception of type 'system.net.webexception' occurred in system.dll not handled in user code

note:the web exception occurs on 5th line last

please suggest methods resolve

public void sendforauthentication()//user defined function sending , receiving requests {     string url = "http://auth.uidai.gov.in/1.6/public/9/9/mltbkycsgymq1zgl3wmzyrnyvsarlljxpom2a-qtpc0zud23shpnqpk";//the host address     streamreader sr1 = new streamreader("d:\\test-signed.xml");//loading xml file stream     string xmldata = sr1.readtoend();     string conn = @"<?xml version=""1.0"" encoding=""utf-8"" standalone=""yes""?>";     xmldata = conn + xmldata;     httpwebrequest req = (httpwebrequest)webrequest.create(url);     byte[] requestbytes = system.text.encoding.utf8.getbytes(xmldata);     req.method = "post";     req.contenttype = "text/xml;charset=utf-8";     req.contentlength = requestbytes.length;     stream requeststream = req.getrequeststream();     requeststream.write(requestbytes, 0, requestbytes.length);     requeststream.close();      httpwebresponse response = (httpwebresponse)req.getresponse();//**here getting webexception**     streamreader sr = new streamreader(response.getresponsestream(), system.text.encoding.default);     string backstr = sr.readtoend();         reader.readtofollowing("title");       file.writealltext("d:\\xml.xml", backstr);   } 

edit: exception "the operation has timed out" though had increased operation time

edit2: above code works fine there problem firewall