How to retrieve the total number of sessions on my Terminal Server?

Type one of the following commands in a command window:

query session /counter

or

query user find "rdp-tcp#" find /c " Active "

If you are running Windows 2003 on your TS, you can also use the following script

(save it as SessionCount.vbs):

Set obji = GetObject("winmgmts:{impersonationLevel=impersonate}!Win32_Service='TermService'")
wscript.echo "Total sessions: " & obji.TotalSessions
wscript.echo "Disconnected sessions: " & obji.DisconnectedSessions

Run the script from a command prompt with:
cscript SessionCount.vbs