We’ve published a new feature today that many vendors have been requesting-  Buyer IP logging and Geo-Location.

DPD now records the IP address of the buyer with each transaction and the information is available on the Purchase Detail page, through the DPD IPN system, and for use on delivery page templates through its own merge tag.

We also use the IP to geo-locate the buyer and display their location on a world map on the Purchase Detail page.  This can help give you an idea where you buyers are coming from (and also it just looks cool).

The technical details:

Buyer IP Address IPN field value:

ip_address

DPD IPN Notification URL Documentation >>

Buyer IP Delivery Page Template Merge Var:  

{{ purchase.ip_address }}

Customizing Your Cart Checkout and Delivery Pages Documentation >>

Instant Payment Notifications (IPNs) are key to how DPD processes and validates PayPal orders. We receive an IPN for each successful purchase that triggers an email and activates the buyer’s purchase. To make sure we are receiving an actual IPN from PayPal to prevent unauthorized download, DPD contacts and verifies each IPN with PayPal. We either get a VALID or INVALID response.

In the past week or so we noticed a spike in failed IPN verifications from PayPal due to the continued rollout of PayPal’s new site. These sort of breakages aren’t uncommon with PayPal and they’re reasonably quick to address these types of issues. We normally don’t have to make any changes on our end before PayPal rolls out a fix. This time was different- There was no fix or even mention of the issue on PayPal’s site and failed IPN verifications were piling up.

So we dug into the logs and figured out what changed. Yesterday we rolled out changes to address the problem. We’re happy to report that we are now seeing a 100% success rate in validating IPNs.

If you are seeing new purchases with the “Error” status, this is most likely caused by an incompatable character encoding in your PayPal account profile having trouble with names and addresses with special characters in them. Please take a moment to enable UTF-8 (item #5) in your PayPal account. This fixes 99% of the remaining IPN validation errors.

What follows is a technical analysis of what happened and how we fixed it. We are posting this in hopes of helping other PayPal developers.

Geeky Programmer Stuff Below…

(Code samples are in PHP.)

The first problem is with generating the validation params. In every IPN validation sample out there, including on PayPal’s own site, you will see the following code to build the validation request:

$req = 'cmd=_notify-validate';

    foreach($params as $key => $value) {
      $value = urlencode(stripslashes($value));
      $req.= "&$key=$value";
    }

There are two things wrong with this snippet. First, PayPal sometimes sends three extra parameters. The most important of those is the cmd parameter. This causes the validation command to switch from _notify-validate to whatever PayPal includes in their IPN and PayPal responds with a 400 Bad Request error. The CONTEXT, myAllTextSubmitID, and form_charset parameters do not have any effect on validation. Adding a unset($params['cmd']); before the foreach fixes the problem.

Secondly, the call to stripslashes is not needed. PayPal likes for you to send back the string exactly as they sent it to you, and they send strings with slashes included. Go figure.

The fixed validation request builder looks like:

$req = 'cmd=_notify-validate';

    unset($params['cmd']);
    foreach($params as $key => $value) {
      $value = urlencode($value);
      $req.= "&$key=$value";
    }

We’re happy to announce beta support for AlertPay as a processor choice for your DPD cart!

Adding an AlertPay product is easy:

• Create a new website
• Choose AlertPay from the drop-down menu and enter your AlertPay login and IPN code
• Login to AlertPay and enable IPN support with the URL we display in your website setup
• Add your product to the new website

DPD supports AlertPay for both instant, single item checkout as well as using our multi-item checkout cart.

We only support digital and key code products at this time. We will be adding tangible support in the future, along with more processor choices.