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Question: How to know if a EOA-Notification is a seller or buyer Notification?
Answer: eBay Platform Notification messages do not specifically state if the message is a Seller or Buyer notification. This information can be determined by using data from within the message itself.
For this example, we will look at the EOA or End Of Auction notification.
1) The first data point to examine is the RecipientUserID. This value indicates the subscribed user, for who the event was generated. We can compare the RecipientUserID, to other ids within the notification, to determine further information.
2) If the RecipientUserID is equivalent to the Seller.UserID, then the notificaiton is clearly a Seller notification.
3) If the RecipentUserID is equivalent to one of the Transaction.Buyer.UserID values, then the notification is clearly a Buyer notification.
4) If the RecipientUserID does not match either of the values in 2) or 3) , it is possible that a user has changed their UserID recently. A GetUser call on any UserID value will return information on when the UserID was last changed, the current UserID, and the EAIS token. You can use this information to match up the RecipientUserID with the Seller or one of the Buyers in a Transaction node for the Item. If the GetUser call is made with a user's old UserID, it will still be valid for up to 30 days. Therefore, you should be able to use the data from GetUser to match any changed UserIDs to a single eBay User account. The EAIS token is unique per user, and does not change with UserID changes.