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Based on the document Gatt Server, there is a note for publishing service with a parameter that said: When a service is both Discoverable and Connectable, the system will add the Service Uuid to the advertisement packet. There are only 31 bytes in the Advertisement packet and a 128-bit UUID takes up 16 of them!
So, if the service UUID is added, there are only 15 bytes left for the payload that you could use.
Thank you.
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