Paypal not responding to rev cgi post

[Thomas McCarthy]

I'm trying to implement a PayPal solution to registering my software. Here's the flow:

1. students/users start up my app and click 'register'
2. A "register_window" rev stack is downloaded and the user chooses some basic options.
3. They click send and my stack generates a key (thanks to Ken Ray for the MACaddress code!) this key and a large random number are sent to a cgi which stores them in my key_database.rev on the server.
4. the button checks for success of this and then takes a preformatted PayPal button and replaces certain items (important: the 'custom' item is pass-through, so I put the large random number there as reference to the generated key) revGoURL opens the browswer with the button info.
5. User (hopefully) completes paying and PayPal contacts my "IPN.cgi" (instant payment notification"). My cgi reads the info, attaches a "cmd=verify" (or something like that) and posts it back for verification.
TROUBLE: nothing comes back
6. Paypal also contacts my "PDT.cgi" which will generate the "Thank you" page. Again, initial info is recieved all right, but posting back for verification fails.

Right now, testing with the PayPal sandbox system, I have to say it's good enough without verification, and my app isn't something folks are likely to spend a lot of time trying to figure out how to steal. Also the initial info I read from the PayPal server is probably enough for me to verify on my own--and decide if I should withold the key or display it/email it out. Still, loose ends make me nervous. Anyone have experience with PayPal?

multas gratias agam,
tm

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