By default, nothing happens when you try to send a file to your Ubuntu machine via Bluetooth. Pairing doesn’t help. I found the solution at Tech Areena:
1) Launch the Personal File Sharing settings, which can by found via a search in the Unity Dash.
2) Enable receipt of files via Bluetooth.
[ERROR] error: File name too long
A common way to install Ubuntu is with an underlying ext4 file system and eCryptfs encrypted home directories. ext4, like many other file systems, has a maximum filename limit of 255 bytes. eCryptfs creates filenames much longer than the original. Compiled Scala classes tend to have long file names since anonymous classes end up in their own files. Therefore, when compiling Scala projects within eCryptfs on ext4, it is easy to get file name too long errors. 🙁