The LINK Protocol
The LINK Protocol specification (by AAH Pharmaceuticals) comprises both the LINK High Level Protocol (for the Transport Layer) and the LINK Low Level Protocol (for the Data Link Layer). These specifications are available from AAH's Customer IT Services Manager.
The LINK Low Level protocol is closely modelled on the Binary Synchronous Communications protocol. Error detection is a combination of parity checking on each byte and longitudinal parity checking on each frame.
| Process Id | Variant |
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| V2 | The caller gave an Access Code with the correct password. |
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| VL | The caller gave a 13 character LINK Account Code. Orders using this variant will not be accepted if the Telecom Options dialog Security field is set to P Require passwords |
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When using the LINK protocols to communicate with GO.EXE:
- The customer should be assigned a 10 character Access Code replacing the 13 character LINK Account Number. If more than 10 characters are presented in the ACC field then the last 10 are taken. Actually, the Access Code comprises a 5 digit number followed by a 5 character password. GO.EXE will disconnect if the password is incorrect, unless the wholesaler accepts LINK Account numbers.
- Any non-numeric occurring within the Quantity field will be ignored except C which indicates the quantity is in cases and B which requests the product be Back Ordered if out of stock.
- It is recommended that small transmission blocks be used (say 4 order lines per block) as the wholesaler's order processing can then proceed concurrently with order transmission.
- Premature Disconnection. The customer end should retain the order for retransmission if it has not received any valid Reply Block because the wholesaler cancels any incompletely received orders. After this point, to avoid duplication of the order, the customer end must not retransmit the order as the customer is explicitly entitled to cancel the reply once it is under way. If the customer end was waiting for the first Reply Block it should warn that the outcome is unknown.
- GO.EXE does not implement the WAK and TTD logic of the LINK protocol as this is considered unnecessary. Reply data is not limited to 2K bytes as the customer end is expected to disconnect when it has received all it can take.
- Each Order Set must include an ACC field with Access Code and valid Password. The ORDER SET, REF, ONO and ORDER END fields are optional and there is no requirement to send an Initialisation Block.
- Any number of Order Sets may be sent in one transmission:
The first Order Set and its Reply Set will be handled as normal up to the point where the terminal should acknowledge the wholesaler's reply by sending the Confirmation Block (the plain text OK).
Instead of sending the Confirmation Block, the terminal may send another Order Set and obtain its Reply Set. This process may be repeated indefinitely. Only send a Confirmation Block to acknowledge the final Reply Set, as the wholesaler will respond by disconnecting. |