How to return invalid value size

[nrfmote]

Hi, I want to write a characteristic, the value size is fixed, for example the size is 4 bytes. When I try to wirte 6 bytes from the client, the first 4 bytes is writed succesfully and the last 2 bytes is droped.I want users know the value size is invalid. How can I return the message of size invalid to the client? Is there any example in the SDK? Thanks.

[nrfmote]

Thanks. If the user write the charactreistic with right size value, nothing need to report.But if the user write more than the max size of the characteristic, I want send a massage to let the user know the error. Which function I can use to send the message or response to inform the user app that the error data size has inputted?