I am working with Expresscheckout on Paypal, For single time Users payment integration. Working flow 1st create token and user redirect to paypal page and success to my return url page. 1.SetExpressCheckout 2. DoExpressCheckoutPayment
My Problem: 1.Now i need to set ipn for this payment system. 2.My notify url is not working on simulator.It gives error(IPN was not sent, and the handshake was not verified. Please review your information.) https://developer.paypal.com/developer/ipnSimulator/
I need some help for this is not set on my side. Please help me out on this.
Thank you in advance.
The handshake error is most likely to occur when your server/keystore config is non-compliant with the upgraded PayPal SSL encryption algorithms.
IPN simulator will connect againest the PayPal Sandbox environment, which has been upgraded with Versign G5 root cert / SHA-2 encryption algorithms (btw this is an industry standard as supposed to be everywhere in 2016). Once your IPN host failed to meet the compliance, the SSL connnection will error out with handshake problems.
Simply check your server by running a connection script against the PayPal sandbox endpoint like this:
openssl s_client -connect api-3t.sandbox.paypal.com:443 -showcerts -CApath /etc/ssl/certs/
If you were not getting an Verify return code: 0 (ok), you would probably have to check the cert/SHA-2 compatibility, following the general instructions that PayPal has published here:
PayPal's Response:
"Thank you for contacting PayPal Merchant Technical Services, I apologize for the delay in responding to your email.
We are aware of this issue with our IPN Simulator and our development team is working on a fix. Until this issue is fixed, I'd suggest running your IPN tests by making payments in Sandbox as we do send IPN requests with every payment.
If you have a similar issue with your payment tests, please let us know and we can take a look.
My apologies for the inconvenience caused."
来源：https://stackoverflow.com/questions/32586711/ipn-was-not-sent-and-the-handshake-was-not-verified-please-review-your-informa