Try who
or who -a
. it displays the user name, TTY/PTS (with id), and the display number (if local) or remote location. See here for the manpages.
This is one local session and two SSH sessions:
:~$ who myuser tty7 2015-09-10 00:44 (:0) myuser pts/2 2015-09-13 19:32 (MyWorkstation.net) myuser pts/4 2015-09-13 19:34 (MyWorkstation.net)