How to add ota function

[Karrthik23]

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I am trying to update my code via OTA and i was confused about how to go about that firstly when i try the serial upload i have 4 bin files (bootloader, partitions, main code etc) when i am trying to do ota which bin file should i be uploading( i am guessing only the main code bin) in the code provided, once the data packet is recieved, addresses have been defined like (pData[0] == 0xFB) what does 0xFB stand for(like corrposponding to which address) other addresses given are 0xFC 0xFD 0xFE if i could get some clarity on that i would be really greatful as i am new to iot and ble implementaitons