I'm trying to use this flow to upload a file to node-red server (Azure) but I always get the answer "Error: only files are allowed".
I checked the node-red folder for the uploaded file - nothing. I created an upload folder but also no success.
So are you trying to send a file from your local machine to be stored on the Azure VM?
Remember NR is running on the Azure VM so it will have access to the files in it’s on device, not the machine you are accessing NR from.
If you want to store files from your local machine, R will have to have network access to the location of those files or you could try the FTP node.