Please define "connection".
Also, what do you mean by "only one authentification with the same user and password"?
I ask this because once I log into the portal, I cannot log in as another user, or even as the same user, until I log out. Even if I open another browser tab or window, and navigate to the portal, I am still logged in as that user.
Perhaps you should describe a use case that you wish to prevent.
Once a user logged into the portal, I would like to forbid another connection by another user with the same login and password.
Nobody can answer?