The steps below are used to create an SFTP server on Ubuntu.

Download Ubuntu Desktop here
We prefer using Filezilla as our SFTP client which can be downloaded here

Open Terminal (CTRL + ALT + T)
sudo apt-get install openssh-server
Stay in sudo mode by typing sudo -s
groupadd sftponly
useradd boris
passwd boris
Enter new password
Retype new password
usermod -G sftponly boris
cat /etc/group
mkdir -p /var/www/vusers/boris
cd /var/www/vusers/
ll (You should see the username listed)
cd boris/
mkdir incoming
ll (You should see the incoming folder listed in the directory)
chown boris incoming/
ll (You should see boris and root have permissions over the incoming folder)
usermod -d /var/www/vusers/boris/ boris
cat /etc/passwd
usermod -s /sbin/nologin boris
cat /etc/passwd (boris will show /var/www/vusers/boris/:/sbin/nologin)
usermod -s /bin/ false boris
cat /etc/passwd (boris will now show /var/www/vusers/boris/:/bin/false)

To summarize the steps we’ve just completed
Created user
Set Password for user account
Created home directory
Set permissions that root is the of main directory
Created the SFTP Folder ‘incoming’
Set permissions that the owner is user ‘boris’
Changed the home directory using usermod
Assigned boris /bin/false shellcd

vim /etc/ssh/sshd_config
Text editor will open
Find the Subsystem line
Place # infront of Subsystem
Create a new line underneath
Type Subsystem sftp internal-sftp (It should look like the following below)

#Subsystem sftp /usr/libexec/openssh/sftp-server
Subsystem sftp internal-sftp

Find a blank line at the bottom
Enter the below as is
#for chroot sftp
Match Group sftponly
ChrootDirectory %h
ForceCommand internal-sftp
X11Forwarding no

Save the changes :wq!
service ssh restart
If that doesnt work just reboot the Ubuntu box using the restart command

Test by using Filezilla by connecting to the Ubuntu IP or hostname using port 22 and the user credentials set.

As a Windows alternative, we have used and recommend JSCAPE MFT Server.
JSCAPE MFT Server is a simple easy to use SFTP server with a GUI.
You can download it for free from here.

Please contact us here if you require any technical support.