What are the possibilities to work remotely through a browser with a Microsoft Windows Server GUI?

Question

User interface

Without installing additional software on the client computer and it is highly desirable without Flash.
You can install anything on Windows Server.
The client can be a computer running any OS with a browser supporting HTML5.
Addition:
There is Microsoft Windows Server on VPS.
5 people will work with him.
We want to administer it remotely, connecting from clients under different operating systems: Linux, MacOS, Windows, iOS and Android.
They have only one thing in common: they all have a browser with HTML5 support.
Based on this, you need an application that can be installed on Microsoft Windows Server, which will allow you to connect to this server through a browser with HTML5.
Prompt for such an application.

Answer 1

guac-dev.org