[OT] Server doesn't send response code

[J. Landman Gay]

I'm not sure who to ask about this. If someone knows where the problem 
is, I'll ask in an appropriate forum somewhere.

I've implemented PayPal's Instant Payment Notification system using an 
old-style CGI on my (non-rev) server. It works fine. Paypal sends a 
notification, my cgi responds, Paypal sends "validated", and I process 
the order. The data always comes in and I always get the validation 
response. That should be the end of it.

But PayPal's sandbox test tool consistently shows an error and replies 
"IPN delivery failed. Unable to connect to the specified URL. Please 
verify the URL and try again." Obviously it did find my server and URL, 
because my script received the data and has responded back to Paypal, 
which in turn has responded with a validation.

So I set up a test button on a fake web page and used their sandbox 
accounts to "buy" from myself. Paypal sends its message, my cgi gets the 
data, sends it back, it's validated, and then Paypal starts resending 
the notification every 2 minutes forever until I turn off the system. 
The IPN docs say Paypal will resend notifications until it gets a 
response. When I look at the IPN history, there is no server response 
code for any of the messages (it should be 200.) The response code field 
is just empty.

So I think what's happening is my server isn't acknowledging receipt of 
the messages, which causes Paypal to think it can't reach me, and it 
keeps resending.

Is the problem a header I should be using? A server problem? Some kind 
of block somewhere? ISP setup? Anyone know where I should start looking?

-- 
Jacqueline Landman Gay         |     jacque at hyperactivesw.com
HyperActive Software           |     http://www.hyperactivesw.com