What is connection handle when programming microcontroller?

[KKIM.6]

I'm trying to use aci_gatt_update_char_ext but it requires connection handle.

But in Custom_STM.c file only have service handle and characteristics handle.

Where can I find connection handle and what is typical variable for it?

[KKIM.6]

The connection handle is  "BleApplicationContext.BleApplicationContext_legacy.connectionHandle" in app_ble.c file.

I'm trying to call this to other files.