1) its a big file, 2) not possible with BLE, with this size it will take 5+ minutes, 3) i am using this plugin https://ionicframework.com/docs/native/bluetooth-le, If you want to have better throughput its advised to use classic bluetooth, maybe this plugin: https://ionicframework.com/docs/native/bl...

Can you confirm in nRF connect logs that MTU has been negotiated and confirmed?
Remember you have to call this before connect (or at least before central asks MTU):

There is few aspects you have take for consideration: 1) file size - what means big file, (for example i am sending 1,3MB+ file over BLE in OTA over BLE), 2) what speed you are expecting, 3) what framework you want to use for android/iOS, for example i found that ionic cordova and flutter does not s...

Yes, but better option may be to make it global variable.

You have to connect to device, then search for services and characteristics before you can read characteristic.

Disconnect error: 0x13 Remote User Terminated Connection I am working with esp v3.3/arduino/AmazonFreeRTOS, esp-idf v4.x and i dont see any problems with it (samsung S9+ with android 10). Maybe there is problem with MTU negotiating. Setting local MTU does not mean its negotiated successfully. Do you...

There is no such thing like default UUID. UUID is set in application.

This is wrong use of printf.
IP2STR macro returns string, to use it with printf you have to use %s, not IPSTR.

You just cant use Serial.print this way:
Try : Or any similar.