I'm trying to get PayPal Here to issue a callback to a FileMaker Go database. It looks like the fmp:// protocol is being used correctly, but seems that there may be some kind of other problem with the callback URL.
Here's the URL that I'm using to call PayPal Here (note that I'm not stripping out the carriage returns from the base64-encoded invoice in my application; this is the actual URL my application sends to the OS, and the invoice appears to be fine in PPH):
paypalhere://takePayment?as=b64&accepted=card%2Cpaypal&returnUrl=fmp:%2F%2F$%2Ffmg_pphTest&step=choosePayment&invoice=eyJwYXltZW50VGVybXMiOiJEdWVPblJlY2VpcHQiLCJkaXNjb3VudFBlcmNlbnQiOjAsImN1cnJl
bmN5Q29kZSI6IlVTRCIsInBheWVyRW1haWwiOiJjcmlzdG9zK3Rlc3RAY3Jpc3Rvc2xjLmNvbSIs
Iml0ZW1MaXN0Ijp7DQogICAgIml0ZW0iOiBbDQogICAgICAgIHsibmFtZSI6IkRpbGl0aGl1bSBD
cnlzdGFsIiwiZGVzY3JpcHRpb24iOiJNYWtlcyBzaGlwIGdvIGZhc3QuIiwidW5pdFByaWNlIjow
LjEsInF1YW50aXR5IjoxMCwidGF4UmF0ZSI6MCwidGF4TmFtZSI6IlRheCJ9DQogICAgXQ0KfX0=
This is the URL that I want to fire (this is just for testing; later on, there will be additional parameters added on to send the payment status, etc., but I can't even get this basic version to work yet):
fmp://$/fmg_pphTest
However, the behavior I'm seeing looks like this is the URL PPH is actually sending:
fmp://
Testing is being done on an iPad 2 running iOS 8.3. Any thoughts/suggestions out there?
A kind soul on the FileMaker Community boards pointed me at a working example, https://github.com/Genecom/FileMakerSampleSolutions. After doing some comparisons, I discovered the issue is due to using base64-encoding of the JSON invoice object. When I changed it to use URL-encoding of the JSON invoice (like the Genecom example), I was able to get the callback URL to work successfully.
I opened an issue on the PayPal Here github project, please feel free to chime in there if you've also experienced this issue (or found countervailing evidence): https://github.com/paypal/here-sideloader-api-samples/issues/26