You can get more info referring BE_Curl_Trace (and you will find that you need to add file name in first parameter URL)
This shows example, https://github.com/GoyaPtyLtd/BaseElements-Plugin/wiki/Functions#BE_FTP_Upload
but sometime you need function to get filename of container, like
GetContainerAttribute ( MyTable::myCNTField ; "filename" )
Yes, you're right!
With BE_Curl_Trace i see also a wrong entry point for my FTP connection.
I fixed it!
Now works properly.