Enthuware

"They cannot create a Socket server"

I understand this for stateless, stateful and MDB, but why not for singleton beans?
I mean why spec prevent for singleton bean also?

Not really sure. May be they will allow it for singleton beans in future versions of the spec
-Paul.

Let me answer this question:

I understand this for stateless, stateful and MDB, but why not for singleton beans?
I mean why spec prevent for singleton bean also?

The spec says any bean is used as a client, not a server. That is why singleton beans cannot be used as a socket server.
On p. 598,

Allowing the instance to become a network server would conflict with the basic function of the enterprise bean - to serve the EJB clients.

Hi,

You said in option 3 that "Only final static fields are allowed for EJB". maybe this sentence should be rephrased, because final is only recommanded.