How to make sure that ipn response come from paypal

I am using paypal payment in my asp.net mvc 3.0 application. I have ipn action which is receiving paypal ipn responce after user payment, is there any way i can check tha开发者_如何学JAVAt incpming request was send from paypal?

PayPal has an IPN verification feature in place that you can use simply by sending the full IPN message you received back to PayPal and appending cmd=_notify-validate.

• If you receive a 'VERIFIED' response back, the IPN is good, and was sent from PayPal.
• If you receive an 'INVALID' response, the IPN was either not sent by PayPal, you didn't receive all the data, or you try to validate the IPN with all the data.

When you receive an IPN message, you should leave the data exactly as it is and send it back to "https://www.paypal.com/cgi-bin/webscr?cmd=_notify-validate&".

I use Send HTTP to troubleshoot my IPNs if my scripts are giving me trouble. You can compare what you're posting to PayPal against what is in your IPN history.

There is a great post published by a PayPal tech on x.com not too long ago, you should check it out for more information.