Question sftp and ftp for assetsbundles

Hi,
A problem I solved puzzles me.
When I uploaded assetBundles to my server using the ftp protocol, they became unreadable when loading : "Error while downloading Asset Bundle: Failed to decompress data for the AssetBundle".
By cons by with sftp protocol, no problem.
I noticed that the file size was changed by the ftp protocol as well.
Not being a master of networks, any idea of the reasons for this difference?
THANKS

 

Ok,
I finally find how to fix this problem.
When I upload a file without an extension like the assetsBundles with my ftp client (here filezilla), it must treat them by default as binary files and not ascii.
Check software settings and no more pbs
If it can help anyone...