How can I logout an open remote SSH session ?

Run tty on your current session, to find out on which tty you are working, so you do not log yourself out from current session

[ ~]  # tty

Run w to show you current users and associated pseudo-terminals(tty).

Assuming that you are logged twice and there one other users on your ssh server logged in from pts/1 ,

Your previous ssh session will be on pts/0 and current on pts/2.

To ditch the session on pts/0 simply kill processes that are associated to it with

# pkill -9 -t pts/0 
Maintained By Amit Maheshwari