If you receive the following error when trying to use SFTP:
Received unexpected end-of-file from SFTP server
This can be solved as follows:
sudo nano /etc/ssh/sshd_config
Comment out the following line:
Subsystem sftp /usr/lib/openssh/sftp-server
Insert the following below the line you commented out:
Subsystem sftp internal-sftp
Save the file with CTRL + o and restart SSH with:
sudo service ssh restart