2012
Table Of Contents
- Instant Payment Notification Guide
- Contents
- Preface
- Introducing IPN
- Implementing an IPN Listener
- Identifying Your IPN Listener to PayPal
- IPN Testing
- IPN Operations on PayPal
- Using Fraud Management Filters With IPN
- IPN Variable Reference
- IPN Transaction Types
- Transaction and Notification-Related Variables
- Buyer Information Variables
- Payment Information Variables
- Auction Variables
- Mass Pay Variables
- Recurring Payments Variables
- Subscription Variables
- Dispute Resolution Variables
- Pay Message Variables
- Preapproval Message Variables
- Adaptive Accounts IPN Messages
- Payment Review Using Notifications
- Revision History
IPN Guide July 10, 2012 11
Introducing IPN
IPN Protocol and Architecture
IPN Messages Generated by PayPal Payments Standard
PayPal generates an IPN message when your customer clicks a PayPal Payments Standard
(previously known as Website Payments Standard) payment button, such as a Buy Now
button, and completes the transaction on PayPal. You can use this notification to kick-off order
fulfillment, enable digital media downloads, store information in a customer relationship
management (CRM) or accounting system, and so on.
The following diagram shows both the web flow and the IPN message authentication protocol:
The numbers in diagram correspond to the following steps:
1. The button action initiates a payment that completes on PayPal
2. PayPal sends your IPN listener a message that notifies you of the event
3. Your listener sends the complete unaltered message back to PayPal; the message must
contain the same fields in the same order and be encoded in the same way as the original
message
4. PayPal sends a single word back, which is either VERIFIED if the message originated with
PayPal or INVALID if there is any discrepancy with what was originally sent
Your IPN listener must implement the IPN authentication protocol (steps 2, 3, and 4 in this
diagram). After successfully completing the protocol, your back-office or administrative
process vets the contents of the message and responds appropriately. For example, if the
payment status for the transaction is “Completed,” your system can print a packing list or
email a password to your customer for downloading digital media.