Telnet can be use as a diagnostic tool in checking the port of your VPS. Like for example, if you are unable to view your website - you can do a telnet to Port 80 (Apache uses port 80) to verify if Apache is responding.
Please note that in Windows Vista and Windows 7, telnet client is disabled by default.
To enable it:
1. Click on "Start Menu" and click on "Control Panel".
2. From the Control Panel, select "Programs and Features".
3. Click on "Turn Windows features on or off".
4. In the list of features, look for "Telnet Client" and tick its checkbox.
5. Click OK and telnet client will be enabled.