Hi,

I am trying to integrate paypal's Simple Pay Standard to my site. I am using the sample code provided by Paypal (shown below)Apart from the sample code I am writing the status to a message file. I have tested the site in my development machine and IPN was working fine. I uploaded the site to the shared web-hosting server and IPN stopped working.
The status in the IPN history shows Failed- HTTP response code 500.

My code is as shown below:

protected void Page_Load(object sender, EventArgs e)
{
try
{
Helper.MsgToFile("Entering PayPal Response Page");
string strSandbox = "https://www.sandbox.paypal.com/cgi-bin/webscr";
string strLive = "https://www.paypal.com/cgi-bin/webscr";
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(strSandbox);

Helper.MsgToFile("Successfully received req params");
//Set values for the request back
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
byte[] Param = Request.BinaryRead(HttpContext.Current.Request.ContentLength);
string strRequest = Encoding.ASCII.GetString(Param);
strRequest = strRequest + "&cmd=_notify-validate";
req.ContentLength = strRequest.Length;


//for proxy
//Dim proxy As New WebProxy(New System.Uri("http://url:port#"))
//req.Proxy = proxy

Helper.MsgToFile("Posted back to Paypal for verification");
//Send the request to PayPal and get the response
StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), Encoding.ASCII);
streamOut.Write(strRequest);
streamOut.Close();
StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream());
string strResponse = streamIn.ReadToEnd();
streamIn.Close();


if (strResponse == "VERIFIED")
{
//check that payment_status is completed
//check that txn_id has not been previously processed
//check that receiver_email is your Primary PayPal email
//check that payment_amount/payment_currency are correct
//process payment

Helper.MsgToFile("Got verified response back from paypal");
}
else if (strResponse == "INVALID")
{
//log for manual investigation
Helper.MsgToFile("Got invalid response back from paypal");
}
else
{
//Response wasn't VERIFIED or INVALID, log for manual investigation
Helper.MsgToFile("Got unknown response back from paypal");
}
}
catch (Exception ex)
{
Helper.ErrorToFile(ex);
}
}

The message file contents are:

[ File writing to log =/PayPalResponse.aspx Date=25/06/2010] Message ===> Entering PayPal Response Page
[ File writing to log =/PayPalResponse.aspx Date=25/06/2010] Message ===> Successfully received req params
[ File writing to log =/PayPalResponse.aspx Date=25/06/2010] Message ===> Posted back to Paypal for verification


The error returned is given below:

[ File Causing Error=/PayPalResponse.aspx Date=25/06/2010] Error Message ===> Unable to connect to the remote server System

Any help as to what is causing this issue is greatly appreciated, since it is a very urgent issue.

Thanks
Meera