Best way to transfer audio files to arduino's SD card over ethernet or wifi?

So, im trying to write an audio file into arduinos Sd card (using arduino mega) I tried to get ftp server to work after 4 hours I gave up :/

the hardware that I got right now are W5100 ethernet shield and esp8266-07 Wifi module I think I should be able to make one of them work somehow I just dont know how yet still trying to figure it out any suggestions or code example of how to make ftp server work? the example code that I got compiled and uploaded but I was never able to connect to the server even after filling up all the network data correctly.

Best way to transfer audio files to arduino's SD card over ethernet or wifi?

The best way to transfer audio files to the SD card is to put the SD card into the computer that has the audio files on it.

Why won't that work?

I know that and thats not an option for me as the hardware will be sealed to IP68 level