GATT notification MTU

[Ricardo Quesada]

TL;DR: Is it possible to change the MTU for att_server_notify() ?

I'm using the le_steamer_client / gatt_streamer_server as reference.

gatt_streamer_server handles the `ATT_EVENT_MTU_EXCHANGE_COMPLETE` event.

But I couldn't find how to trigger that event. Is there a way that from the server I can ask the client to increase the MTU ?

I'm only interested in increasing the MTU when sending the payload using `att_server_notify()`.

Thanks!

[Matthias Ringwald]

Hi Ricardo

TL;DR: not really, but you can try a GATT Client query :)

Core v5.4/ATT says that the GATT Client sends the ATT_EXCHANGE_MTU_REQ. =
You cannot do anything about that.
On the other hand, if a device is both GATT Client and Server, a device =
shall use the same MTU for both roles.
Also, there's some indication that both sides use a single MTU for both =
directions.

So, you can try to make a GATT Client query to the remote side, which =
will trigger an MTU Exchange by BTstack,
which then should also be valid for the GATT Server :)

Taking a step back: what device does send MTU Exchange in Client role?

Cheers
Matthias

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[Ricardo Quesada]

I'll play with GATT query. Many thanks!

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