EJB 2.0 Spec Clarification

Question

I quote directly from the EJB2.0 Specification:
" Clients are not allowed to make concurrent calls to a stateful session object. If a client-invoked business
method is in progress on an instance when another client-invoked call, from the same or different client,
arrives at the same instance of a stateful session bean class, the container may throw the
java.rmi.RemoteException to the second client [4] , if the client is a remote client, or the
javax.ejb.EJBException, if the client is a local client. This restriction does not apply to a state-less
session bean because the container routes each request to a different instance of the session bean
class. "
Now the part that im confused is this:
'If a client-invoked business
method is in progress on an instance when another client-invoked call, from the same or different client'
As far as I understand,Stateful Sessions are Client-specific,that is One instance services atmost one client.So that part about "same or different client" confused me.What does it mean? Can anyone help?
Thanks in Advance.
Ameya

Answer 1

You can look at that part of the spec as applying to the app server vendors. A little re-wording:
"If a client-invoked business method is in progress on an instance when another client-invoked call, from the same or different client", your app server must throw a java.rmi.RemoteException or javax.ejb.EJBException, depending upon whether the request is remote or local.