Integration Guide

Table Of Contents
Implementing the Instant Update API
Setting Up the Callback
7
82 May 2010 Express Checkout Integration Guide
Setting Up the Callback
To set up the callback, you establish a connection with PayPal by providing the location where
PayPal calls your callback server, along with your shipping options.
To start, you must build and operate a secure, reliable, and fast callback server that computes
shipping options, corresponding insurance options, and tax, based on your business rules. To
verify that callback requests originate from PayPal, check the IP addresses requests against the
list of IP addresses for *.paypal.com, as described in the
go-live checklist.
The HTTP protocol to specify in your callback URL depends on the integration environment
you are using:
z The callback URL must start with HTTPS for production integration.
z The callback URL must start with HTTP or HTTPS for PayPal Sandbox integration.
In the call to SetExpressCheckout, you must complete the steps 1 through 3 below. Steps 4
and 5 are optional:
1. Provide line-item details for the merchandise the buyer selected. For details on how to
integrate line-item details, see Chapter 7, “Customizing Express Checkout,” in the
Express
Checkout Integration Guide.
2. Provide the URL to your callback server. PayPal validates the URL as described above.
3. Provide values for the flat-rate shipping options. For each option, specify:
Option name (L_SHIPPINGOPTIONNAMEn)
Option amount (L_SHIPPINGOPTIONAMOUNTn)
The shipping option to appear in the drop-down menu as the default (true)
(L_SHIPPINGOPTIONISDEFAULTn).
NOTE: Set L_SHIPPINGOPTIONISDEFAULTn to true (default) for one and only one
shipping option. Set L_SHIPPINGOPTIONISDEFAULTn to false for each of the
remaining options.
If required, an adjusted value for TAXAMT
If required, an adjusted value INSURANCEAMT
4. If necessary to adjust the callback timeout (default: 3 seconds), provide a value from 1 to 6
for the CALLBACKTIMEOUT parameter.
5. Optionally, provide values for any of the shipping option description details fields listed
below:
Option weight (L_ITEMWEIGHTVALUEn, L_ITEMWEITHTUNITn)
Option height (L_ITEMHEIGHTVALUEn, L_ITEMHEIGHTUNITn)
Option length (L_ITEMLENGTHVALUEn, L_ITEMLENGTHUNITn)
Option width (L_ITEMWIDTHVALUEn, L_ITEMWIDTHUNITn)