How can I view active remote connections (RDP) to a Windows server?

How can I view, who is currently connected to a server (Windows 2012) with a remote desktop client? I am myself connected to this server via RDP.

This question offers a solution to get IP addresses with established connections. I would be interested in a list of users or their sessions and when these sessions were active the last time.

You can type "Query User" into a command prompt on the remote machine to get a very quick look

Run the "qwinsta" command on the server, or with the /server:servername switch.

>qwinsta /?
Display information about Remote Desktop Sessions.

QUERY SESSION [sessionname | username | sessionid]
              [/SERVER:servername] [/MODE] [/FLOW] [/CONNECT] [/COUNTER] [/VM]

  sessionname         Identifies the session named sessionname.
  username            Identifies the session with user username.
  sessionid           Identifies the session with ID sessionid.
  /SERVER:servername  The server to be queried (default is current).
  /MODE               Display current line settings.
  /FLOW               Display current flow control settings.
  /CONNECT            Display current connect settings.
  /COUNTER            Display current Remote Desktop Services counters informati
on.
  /VM                 Display information about sessions within virtual machines
.

You can also reset an RDP session with the "rwinsta" command:

>rwinsta /?
Reset the session subsytem hardware and software to known initial values.

RESET SESSION {sessionname | sessionid} [/SERVER:servername] [/V]

  sessionname         Identifies the session with name sessionname.
  sessionid           Identifies the session with ID sessionid.
  /SERVER:servername  The server containing the session (default is current).
  /V                  Display additional information.

You can see in the Task manager users Tab

the tsadmin.msc command will give you a nice GUI with information and control over windows RDP sessions