The Object Request Broker (ORB) is a vital component in distributed computing and middleware technologies. It serves as an intermediary between distributed objects, allowing them to communicate and exchange data seamlessly across a network. The ORB abstracts the complexity of inter-process communication, enabling developers to focus on application logic rather than low-level network interactions.

Key Features of Object Request Broker:

1. Distributed Object Communication: The ORB facilitates communication between distributed objects, regardless of their physical location. It abstracts the underlying communication protocols, making it easier to develop applications that span multiple machines.
2. Object Marshaling and Unmarshaling: When an object sends data across the network, it needs to be converted into a format suitable for transmission (marshaling). The receiving end must then convert the data back to its original format (unmarshaling). The ORB handles this serialization and deserialization process transparently.
3. Interface Definition Language (IDL): To ensure interoperability between different programming languages and platforms, the ORB typically uses an Interface Definition Language (IDL). IDL defines the interfaces of distributed objects, enabling clients and servers to understand each other’s methods and data structures.
4. Location Transparency: Clients of distributed objects interact with them as if they were local, without being aware of their physical location. The ORB takes care of routing requests and responses to the appropriate objects.
5. Security: Many ORBs provide security mechanisms to authenticate clients, authorize access to objects, and encrypt communication to protect sensitive data.

ORB Architecture:

The ORB architecture consists of several components:

1. Client Stub: The client-side interface to the ORB, responsible for marshaling method calls and sending them to the server.
2. Server Skeleton: The server-side interface to the ORB, responsible for unmarshaling method calls, invoking the appropriate object methods, and sending the results back to the client.
3. ORB Core: The core of the ORB, managing object references, object activation, and communication protocols.
4. Naming Service: An optional component that allows clients to locate objects by name rather than their physical location.

Common ORB Implementations:

• CORBA (Common Object Request Broker Architecture): A standard for ORBs defined by the Object Management Group (OMG). It is language-agnostic and allows objects to communicate across multiple platforms.
• Java RMI (Remote Method Invocation): An ORB implementation in Java that facilitates communication between Java objects running on different Java Virtual Machines (JVMs).
• Microsoft DCOM (Distributed Component Object Model): An ORB implementation for Windows platforms, enabling communication between objects in the Microsoft ecosystem.

Conclusion:

The Object Request Broker plays a crucial role in enabling seamless communication between distributed objects in a networked environment. By abstracting the complexity of inter-process communication, the ORB simplifies the development of distributed applications and allows developers to focus on building robust and scalable systems. Different implementations of ORBs, such as CORBA and Java RMI, cater to specific platforms and languages, providing flexibility and interoperability in distributed computing.