Samir,
I'd suggest using the the
Push Notification and having all clients subscribe to this service. Then once the notification is received, the client would check if it was it who generated started the operation and then act appropriately.
In your case, you'd need something other than the Principal to identify the user. (i.e. IP)
Have you created a custom IPrincipal where you have this 'something else' that would differentiate one 'user' from another?
I still think that the best/simplest approach would be having different users with the same role.
Silvio.