Question

I have tried to integrate paypal sandbox with my project in asp.net.

Redirection to paypal sandbox working extremely fine ! You can check out your cart ! You can make payment ! But the problem is when paypal set redirection to my Success.aspx page !

I got the error as

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 192.168.0.101:808

I am using stream writer Object !

Wait Let me post my code !

this is page_load even of Success.aspx

   protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                // Used parts from https://www.paypaltech.com/PDTGen/
                // Visit above URL to auto-generate PDT script

                authToken = WebConfigurationManager.AppSettings["PDTToken"];

                //read in txn token from querystring
                txToken = Request.QueryString.Get("tx");


                query = string.Format("cmd=_notify-synch&tx={0}&at={1}", txToken, authToken);

                // Create the request back
                string url = WebConfigurationManager.AppSettings["PayPalSubmitUrl"];
                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);

                // Set values for the request back
                req.Method = "POST";
                req.ContentType = "application/x-www-form-urlencoded";
                req.ContentLength = query.Length;

                // Write the request back IPN strings
                StreamWriter stOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII);
                stOut.Write(query);
                stOut.Close();

                // Do the request to PayPal and get the response
                StreamReader stIn = new StreamReader(req.GetResponse().GetResponseStream());
                strResponse = stIn.ReadToEnd();
                stIn.Close();

                // sanity check
                Label2.Text = strResponse;

                // If response was SUCCESS, parse response string and output details
                if (strResponse.StartsWith("SUCCESS"))
                {
                    PDTHolder pdt = PDTHolder.Parse(strResponse);
                    Label1.Text = string.Format("Thank you {0} {1} [{2}] for your payment of {3} {4}!",
                        pdt.PayerFirstName, pdt.PayerLastName, pdt.PayerEmail, pdt.GrossTotal, pdt.Currency);
                }
                else
                {
                    Label1.Text = "Oooops, something went wrong...";
                }
            }
        }

This sentence creates error !!

StreamWriter stOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII);

These type of exception occurs

    Exception Details: System.Net.Sockets.SocketException:
 A connection attempt failed because the connected party did
 not properly respond after a period of time, 
or established connection failed because connected
 host has failed to respond 192.168.0.101:808

Answer 1

First off, do not mix PDT and IPN – just use IPN. Go into PayPal admin and make sure that the return URL is NOT set there and that PDT is NOT enabled.

There is an IPN class available online just for this purpose – some more info (Caveat: my own blog post):

http://codersbarn.com/?tag=/paypal

http://paypalipnclass.codeplex.com/releases/view/31282