There are several ways to know who are still logged in and where (IP Address) they come from on your Linux server.
[root@test ~]# w 06:01:53 ... USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT steven tty1 - 05:56 5:07 0.00s 0.00s -bash root pts/0 192.168.5.3 05:52 0.00s 0.01s 0.00s w
[root@test ~]# who steven tty1 2014-05-04 05:56 root pts/0 2014-05-04 05:52 (192.168.5.3)
[root@test ~]# last | grep "still logged in" steven tty1 Sun May 4 05:56 still logged in root pts/0 192.168.5.3 Sun May 4 05:52 still logged in In the above example, you can see there is one user from local console and the other is from a remote server (IP Address 192.168.5.3).