How to prevent a client from writing an invalid value into a GATT characteristic?

RE: How to prevent a client from writing an invalid value into a GATT characteristic?

Christian22 — Fri, 26 Apr 2019 17:03:43 GMT

Thank you. This helps me a lot.

RE: How to prevent a client from writing an invalid value into a GATT characteristic?

Andy — Fri, 26 Apr 2019 16:50:01 GMT

If you want to let the central know that something went wrong, use an error code. Otherwise, you can just authorize the write, let the central think that everything is fine and ignore the write internally. It's up to you.

RE: How to prevent a client from writing an invalid value into a GATT characteristic?

Christian22 — Fri, 26 Apr 2019 16:40:03 GMT

Hi Andy,

Thank you very much for your fast response.

Do you know which error code I have to choose in response to a write request? In the core spec 5.0 Vol 3, Part G, 4.9.3 I found:

"If the Characteristic Value that is written is the wrong size, or has an invalid value as defined by the profile, then the value shall not be written and an Error Response shall be sent with the Error Code set to Application Error by the server."

Does this mean I have to use an error code between BLE_GATT_STATUS_ATTERR_APP_BEGIN and BLE_GATT_STATUS_ATTERR_APP_END if a client tries to write an invalid value?

RE: How to prevent a client from writing an invalid value into a GATT characteristic?

Andy — Thu, 25 Apr 2019 15:13:05 GMT

Yes, write with authorization is the way to go in this case :)