how to send "MTU Exchang Request" in Gatt Server of ESP32S3

[workhard10]

Hello everyone,

I want to use a ESP32-S3-DevKitC-1 to simulate a Nuki Lock, and just let my NukiLock(simulated by ESP32S3) connet with Nuki Fob.

I use nrf52840 dongle in Wireshark to watch the Bluetooth package between real Nuki Lock and Nuki Fob and find that the "MTU Exchange Request" is be sent form Nuki Lock(Server) to Nuki Fob(Client). see my first Wireshark picture "NukiLock-Fob.JPG". mark Nr.1 and Nr.2

As I said, I have built/simulated a Nuki Lock with ESP32S3. when the NukiLock(ESP32S3) connects with Nuki Fob, they miss the "MTU Exhcange" action, so they don't work and can not be connected together... see my second Wireshark picture"ESP32-Fob.JPG".

So my question is how to send "MTU Exchang Request" from ESP32S3(Gatt Server) to Nuki Fob(Gatt Client)? I know there is a API

Code: [Select all] [Expand/Collapse]

1. esp_err_t esp_ble_gattc_send_mtu_req(esp_gatt_if_t gattc_if, uint16_t conn_id)

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, but it is only for Gatt Client,...

I also read the BLUETOOTH SPECIFICATION Version 5.0 | Vol 3, Part G: 4.3 SERVER CONFIGURATION and 4.3.1 Exchange MTU, it means that we can configure the Gatt Server for Exchange MTU, but how in ESP32S3?

I look forward to you feedback! thank you!