From the RDS server you can use Task Manager > Users to view current active user sessions.
Alternatively from Powershell either:
Using Teamviewer with RDP in Windows you may receive the following error when an RDP session is closed or minimised.
The screen cannot be captured at the moment. This is probably due to fast user switching or a disconnected/minimized remote desktop session
To get around this make sure Teamviewer is installed then:
1. Get the server ID from either Help > About Teamviewer or click on the bulb icon next to the ID
2. Set the unattended password in Extras > Options > Security.
Tested as of Teamviewer 11
When using Windows RDP you may encounter the error message ‘The terminal server has exceeded the maximum number of allowed connections’. You can delete open sessions or use the admin switch to administer the server.
At the command prompt:
To administer the server:
mstsc /v:<server> /admin
To obtain a list of current sessions:
query session /server:<server>
To close a session – [ID] can be found from session list
reset session [ID] /server:<server>