Paypal sandbox IPN return INVALID - paypal

Question

I am trying IPN callback, using servlet. The code I am using is provided by paypal for verifying the ipn data. But every time i getting a INVALID response.
Here is the code:
Enumeration en = req.getParameterNames();
String str = "cmd=_notify-validate";
while (en.hasMoreElements()) {
String paramName = (String) en.nextElement();
String paramValue = req.getParameter(paramName);
//str = str + "&" + paramName + "=" + URLEncoder.encode(paramValue,"UTF-8"); // for UTF-8 i set the encode format in my account as UTF-8
//str = str + "&" + paramName + "=" + URLEncoder.encode(paramValue,"ISO-8859-1");// for ISO-8859-1 i set the encode format in my account as ISO-8859-1
str = str + "&" + paramName + "=" + URLEncoder.encode(paramValue); //default as provided by paypal
}
URL u = new URL("http://www.sandbox.paypal.com/cgi-bin/webscr");
URLConnection uc = u.openConnection();
uc.setDoOutput(true);
uc.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
PrintWriter pw = new PrintWriter(uc.getOutputStream());
pw.println(str);
pw.close();
BufferedReader in = new BufferedReader(new InputStreamReader(uc.getInputStream()));
String res = in.readLine();
in.close();
if (res.equals("VERIFIED") || !res.equals("VERIFIED")) {
//Update database...
} else if (res.equals("INVALID")) {
//INVALID
}
I have checked all three possibilities provided by paypal in case paypal return INVALID as follow:
1) Missing Parameters - As I am send all the parameters no issue of missing parameters
2) Invalid URL. - I am using sandbox so URL is : http://www.sandbox.paypal.com/cgi-bin/webscr
3) Character encoding. - Tried with character encoding same as paypal account setting parameter encoding.
the request I am sending back to paypal using following parameters:
cmd=_notify-validate&last_name=User&test_ipn=1&address_name=Test+User&txn_type=web_accept&receiver_email=sellr1_1252495907_biz%40gmail.com&residence_country=US&address_city=San+Jose&payment_gross=&payment_date=01%3A55%3A04+Sep+26%2C+2009+PDT&address_zip=95131&payment_status=Completed&address_street=1+Main+St&first_name=Test&payer_email=buyer1_1252495751_per%40gmail.com&protection_eligibility=Eligible&payer_id=BXBKS22JQCUWL&verify_sign=AOMkeg7ofCL7FJfioyWA19uCxD4XAgZirsjiGh8cUy1fd2YAqBwOkkst&payment_type=instant&business=sellr1_1252495907_biz%40gmail.com&address_country_code=US&mc_fee=0.64&address_status=confirmed&transaction_subject=True+Up&quantity=1&notify_version=2.8&mc_currency=EUR&custom=&address_state=CA&payment_fee=&handling_amount=0.00&payer_status=verified&shipping=0.00&item_name=True+Up&tax=0.00&username=hannonj&charset=windows-1252&item_number=567&mc_gross=10.00&txn_id=7F456350BS7942738&receiver_id=MASSU6BSR9SC2&address_country=United+States
Please , can any one direct me to proper direction? I am not getting what is wrong the code or the URL or anything else. I tried all the possibilities. Please help me.

Answer 1

An “INVALID” message is due to the following reasons:
Check that your are posting your response to the correct URL, which is https://www.sandbox.paypal.com/cgi-bin/webscr or https://www.paypal.com/cgi-bin/webscr, depending on whether you are testing in the Sandbox or you are live, respectively.
Verify that your response to the test IPN message contains exactly the same variables and values as the test message and that they are in the same order as in the test message. Finally, verify that the original variables are preceded by a cmd=_notify-validate variable.
Ensure that you are encoding your response string and are using the same character encoding as used by the test IPN message. (for example, I can see that he is using letters with umlaut and other symbols like “/”, etc).
With regard to the last point, the merchant can try to change the encoding language in use in his PayPal account, following the steps below:
Login on you PayPal account
Click on Profile
Click on “My Selling Preferences” tab
Click on “PayPal Button Language Encoding” (at the end of the page)
Click on "Other Options"
Select from the drop down menu: UTF-8
Choose the same charset also for the second option, which is related to IPN
Click “Save”
If the issue persists, we recommend to review the script in use, PayPal has some IPN code samples available at: https://github.com/paypal/ipn-code-samples
For additional information I include the link: https://developer.paypal.com/webapps/developer/docs/classic/ipn/integration-guide/IPNTesting/#id091GFE00WY4

Answer 2

I'm pretty sure the URL to send to is just "www.sandbox.paypal.com", see chapter 4 of Sandbox User Guide, and well, this is what I put for my own code (incidentally, for live, it is also just "www.paypal.com", for their sample code)

Answer 3

Thank you guys for your reply.
ohhh I solved it at last.
Actually in notify URL I also added a username parameter. Paypal want the parameter values for IPN same as it return to the servlet.(You can get it as req.getParameterNames()). As I have username parameter extra, which is not known to paypal. Paypal was returning INVALID.

Answer 4

Remember paypal's sandbox has completely different credentials. You must have development account and be logged into development panel to use sandbox.

Answer 5

If you're testing Paypal IPN over SSL, you will have to use ssl://www.sandbox.paypal.com on the port 443

Answer 6

I ran into multiple problems layered on top of each other before I could get Paypal IPN working - it kept returning INVALID but was not specific about which part I was getting wrong, unfortunately.
Things I got wrong:
Sandbox - if you use the Sandbox you need to use the entire Sandbox environment. It requires creating a new, separate account on the Paypal Sandbox website. The Sandbox API credentials it sets up under your regular account are not enough. You then use that separate Paypal account to file fake transactions on the Paypal Sandbox website, and watch them come across IPN on the Sandbox endpoint. The need for this second account is not obvious or clear at all in setting up API access. Also, switching between Sandbox and Live requires more than switching the URL, you need to switch the credentials. So a simple compile flag alternating a string isn't going to cut it.
Live - if you use the Live environment a number of things will get in your way. For us, it took a long time for Paypal to open up "Business" access to us. It wouldn't provide us anything over the API until that was enabled. When we initially applied we were flatly denied with no explanation or timeline to resolve it. A month later ish of taking payments (with no API to keep us up to date with those payments) it seemed to just magically start working.
Code example - the code example provided by Paypal is outdated, and has some clear issues. Here's an example that uses modern TPL/async:
// Send the verification back to Paypal in the format Paypal requested
var verif = (HttpWebRequest)WebRequest.Create(ipnVerifyUrl);
verif.Method = "POST";
verif.ContentType = "application/x-www-form-urlencoded";
var param = req.BinaryRead(req.TotalBytes);
var sRequest = Encoding.ASCII.GetString(param);
sRequest = "cmd=_notify-validate&" + sRequest;
verif.ContentLength = sRequest.Length;
using (var streamOut = new StreamWriter(verif.GetRequestStream(), Encoding.ASCII))
{
await streamOut.WriteAsync(sRequest);
}
// Send it
using (var re = await verif.GetResponseAsync())
{
var s = await HttpWebRequestAsync.GetFullResponseStringAsync((HttpWebResponse)re);
// Log the response (s)
}
Besides this code actually working (This is exactly what we have in Production, with some of our logging library calls stripped out), this code won't freeze a thread while waiting on network.
The awaits allow the thread to step away while the network does its thing, both in writing the verification request to Paypal, and in receiving the response back, both of which could be a long time.