The Enterprise Server supports a standard set of protocols and formats that ensure interoperability. Among these protocols are those defined by CORBA.
The CORBA (Common Object Request Broker Architecture) model is based on clients requesting services from distributed objects or servers through a well-defined interface by issuing requests to the objects in the form of remote method requests. A remote method request carries information about the operation that needs to be performed, including the object name (called an object reference) of the service provider and parameters, if any, for the invoked method. CORBA automatically handles network programming tasks such as object registration, object location, object activation, request de-multiplexing, error-handling, marshalling, and operation dispatching.
The Object Request Broker (ORB) is the central component of CORBA. The ORB provides the required infrastructure to identify and locate objects, handle connection management, deliver data, and request communication.
A CORBA object never talks directly with another. Instead, the object makes requests through a remote stub to the ORB running on the local machine. The local ORB then passes the request to an ORB on the other machine using the Internet Inter-Orb Protocol (IIOP for short). The remote ORB then locates the appropriate object, processes the request, and returns the results.
IIOP can be used as a Remote Method Invocation (RMI) protocol by applications or objects using RMI-IIOP. Remote clients of enterprise beans (EJB modules) communicate with the Enterprise Server via RMI-IIOP.
An IIOP listener is a listen socket that accepts incoming connections from the remote clients of enterprise beans and from other CORBA-based clients. Multiple IIOP listeners can be configured for the Enterprise Server. For each listener, specify a port number, a network address, and optionally, security attributes.