Find the answer to your question
Q. What is the eBay requirement for the Platform Notification Delivery URL?
A. Notification Delivery URL must be accessible on the public internet ( i.e. not running on localhost or behind a firewall).
Q. Can I run my notification listener on a non-standard port?
A. No, you must host your notification listener on port 80. You will get the com.ebay.kernel.service.invocation.client.exception.ConnectionTimeoutException if you runs Notification listener on a non-standard port like 81 which is blocked by the eBay firewall and/or ISP (Internet Service Provider).
Q. If the notifications cannot be received on URLs that require VPN access then how can we test notifications?
A. You can start with email notifications as documented in the Receiving Notifications by Email ( search 'Receiving Notifications by Email' and save the received email notification payload. Then send the notification payload to the 'Platform Notification Delivery URL' you specified in ApplicationURL via the simple HTML form. This method allows you to test your notification listener code without going to eBay.