97 Resend
- Request
- 97 (device) or 96 (library system)
- Response
- the message last sent
- Set
- core
- Position in BX
- 5
This command pair is the odd one out: It has no response code, and either side may send it. Its sole purpose is to request a message that arrived damaged.
| Code | Who sends | Meaning |
|---|---|---|
97 |
device | "send your last message again" |
96 |
library system | the same in the other direction |
Structure#
97<AZ...>
96<AZ...>
Both messages consist of nothing but the command code and the checksum. They carry no sequence number – they belong to no transaction but refer to whatever last went across the line.
Procedure#
If the checksum of a received message does not match, the recipient sends the resend request. The sender then transmits its last message again unchanged – with the same sequence number and the same checksum as the first time.
That is the decisive point: The message is repeated, not regenerated. A checkout the library system has already booked is therefore not booked a second time; the device merely receives the lost response again.
If the sender has sent nothing at all yet, it answers with a resend request of its own. If the other side answers a resend request with another resend request, the connection counts as broken: The device opens a new one and logs in again.
Example#
97AZFEF5<CR>
121YUU20260728 143012AOBVS|AA1140360000042|AB1140360000123|AJEnde, Michael: Momo|AH25.08.2026|AY3AZE64F<CR>
The device received the checkout response damaged and requests it again; the library system sends the same message once more.