Thanks a lot @TirzahC & @Fiat Lux - ASIA 

We are on multi user mode. So everyone in the team is able to access simultaneously.

It's just that like you said when i'm logged on QBD application at server and when i forgot to log out and try logging in again at my local machine. I get this error message user already logged in

So the only solution as per your answers are

a) Logout from server machine

b) Purchase another license and create a new user if i want to log in simultaneously at both the machines