I’ve just come across a terminal server that wouldn’t let me log on. Turns out the maximum number of users the terminal server is licensed for has been exceeded. #

Thusly, from another machine on the network, we open a command prompt and type
qwinsta /server:<servername> #

This will give a list of the terminal server sessions on that server, note the ID number (aka sessionid) as we use them in the following commands. #

We can reset a session by using
rwinsta <sessionid> /server:<servername> #

or we can disconnect the session with
tsdiscon <sessionid> /server:<servername> #

or we can logoff a session with
logoff <sessionid> /server:<servername> #

Dan Rigsby has more info as does Scott Forsyth. #