Errors
Error replies, which results are definite, recovery after a dropped connection, and concurrency.
An error reply has a code and a message and nothing else:
{ "error_code": "PP_A2A_012", "error_message": "İşlem sırasında hata oluştu: Kart reddedildi" }Detect errors by the presence of error_code. error_message is always
Turkish and can be shown to the cashier; branch your logic on the code.
Error codes
| Code | Meaning | Result |
|---|---|---|
PP_A2A_001 | The request is empty. | Not started |
PP_A2A_002 | data is missing or is not an object. | Not started |
PP_A2A_003 | api_key / secret_key missing or invalid. | Not started |
PP_A2A_004 | Invalid EOD: is_all is false and types is empty. | Not started |
PP_A2A_005 | Invalid PARAMETERS: is_all is false and types is empty. | Not started |
PP_A2A_006 | Invalid request parameter. | Not started |
PP_A2A_007 | Unexpected error while handling the request. | Unknown |
PP_A2A_008 | header is missing. | Not started |
PP_A2A_009 | transaction_type is missing or unknown. | Not started |
PP_A2A_010 | A header field this command needs is missing. | Not started |
PP_A2A_011 | Nobody is logged in to POS+ on the device. | Not started |
PP_A2A_012 | The operation failed: declined, cancelled by the user, order closed … | Definite |
PP_A2A_015 | The device is busy with another request. | Not started |
PP_A2A_016 | TRANSACTION_RESULT: no transaction with that id. | Definite |
PP_A2A_017 | Authentication could not be performed (device offline or server unreachable). | Not started |
Recovery
The device completes an operation even when your connection drops. If you send a payment and do not get a reply — a socket error, a timeout, your software restarted — the customer may already have paid.
Never send the payment again just because the reply did not arrive. Query first. Charging twice is the most expensive integration bug.
- Before sending a payment, persist the
order_codeas result unknown. - If the reply arrives, record it and clear the flag.
- Otherwise open a new connection and send
ORDER_RESULTwith thatorder_code(orTRANSACTION_RESULTif you have the transaction id). amount_due: 0→ paid. Otherwise nothing was collected and you may start a new payment.- Do the same at start-up for every order still flagged.
The same applies to PP_A2A_007.
Concurrency
A POS+ device runs one operation at a time, across all clients — another
till, another connection or an App2App app on the device itself. A request that
arrives while one is running is rejected at once with PP_A2A_015.
- Do not send requests in parallel, not even on separate connections.
- On
PP_A2A_015, wait and retry; show the cashier that the device is busy. - Within one connection, requests are handled in order, so a queue on your side is only needed when several parts of your software share a device.