What’s the best application that allows multiple concurrent users logged into a server without disturbing each other?

Question

We have a server located at our office & we have 6 employees distributed over 6 different cities. We are facing a case where these 6 employees sometimes try to login into the server through internet concurrently and perform different tasks like ( opening our ERP system, checking some emails, deleting some files) without disturbing each other i.e. each employee will work independently from each other.

Of course, we would prefer a software which provides these features over the internet to pass all the firewalls or any obstacles.

I have found some applications like TeamViewer but only allows one user to have full control

Answer 1

What is OS running on your server. Assuming you have windows server you can use Remote Desktop Sessions - http://msdn.microsoft.com/en-us/library/aa383052(v=VS.85).aspx