Some time ago because more users need to remotely connect to Windows Server 2012, but found a half-day also did not find Remote Desktop management, and finally found the following method from the search, tested feasible!
Open the registry and enter the path: [hkey_local_machine\system\currentcontrolset\control\terminal Server]
Locate Fsinglesessionperuser modified to its value of 0 (if this key does not exist, a new DWORD value named Fsinglesessionperuser is required).
Effect:
Reference:
1. Restrict Users to a single Session
2. Force a single session or allow multiple Remote Desktop sessions per user
3. Windows2012 the "Restrict each user to only one session" Method for Remote Desktop
4. Remote Desktop restricts users to use the same session
5. Clear one account only one session limit
Windows Server 2012 Configures multi-user remote Desktops