BLE Sniffer shows ATT write but no UUIDS?

[AndrewMohawk]

Hey,

I'm trying to follow a few guides on sniffing BLE connections (eg https://hackaday.com/2021/03/23/a-crash-course-on-sniffing-bluetooth-low-energy/ ) with an NRF52-DK (I have dongle and DK) and I have everything configured in a similar manner, but whenever I see the Write commands I dont see either Service UUID or UUID fields within Wireshark:

I've included the full pcap as well. 

LocateHIDReaderR10.pcapng

Is there something simple I am missing here? I've tried with different dongles and DK and I get the same result.

Thank you!

Andrew

[Kenneth]

The GATT database server will have a lot of services and characteristics with different UUID's. Typically when a peer is doing a database discovery it will receive all the UUID's with a unique 16-bit handle for each "entry" in the GATT database, the handle is typically an incrementally ordered value for each service and characteristic in the GATT database. All communication (write, read, notifications) will be done using the 16-bit handle, this according to BT specifications.

Kenneth

[AndrewMohawk]

Hi Kenneth,

I am not following how this would relate to why I dont see the UUIDs. If you look at this guide here: https://daniellethurow.com/blog/2021/9/22/using-adafruits-bluetooth-sniffer

You see the following screenshot (and is similar across many other guides as well):

[Kenneth]

The sniffer will typically only show what is on-air, and the UUID is not sent on-air during normal write, read and notifications. However I do believe that if during the same connection there was a database discovery prior, the sniffer software may be able to find which UUID the handle belong to, and display it alongside the handle.

Kenneth