RMI (Remote Method Invocation) Project

A comprehensive Java Remote Method Invocation (RMI) application that demonstrates client-server communication and remote object invocation.

Project Overview

This project implements a classic RMI example where a server hosts multiple product objects and clients can remotely access these products to retrieve their information (name, description, and price) over the network.

Architecture

System Components

Client Side
├── Client.java               # Main client application
└── Product.java              # Remote interface for product operations

Server Side
├── Server.java               # Main server application  
├── Product.java              # Remote interface (same as client)
├── ProductImpl.java          # Implementation of Product interface
└── ProductImpl.class         # Compiled implementation

Entry Point
└── Main.java                 # Simple hello world example (not part of RMI system)

Key Components

1. Remote Interface (Product.java): Defines the contract for remote operations

   • getName() - Returns product name
   • getDescription() - Returns product description
   • getPrice() - Returns product price

2. Implementation (ProductImpl.java): Implements the remote interface

   • Contains product data (name, description, price)
   • Provides actual implementations of remote methods

3. Server (Server.java): RMI Server Application

   • Creates multiple product instances
   • Exports objects for remote access
   • Registers objects in RMI registry
   • Hosts 4 different products (Product1-4)

4. Client (Client.java): RMI Client Application

   • Connects to RMI registry
   • Looks up remote objects by name
   • Invokes remote methods to get product information

Setup Instructions

Prerequisites

• Java Development Kit (JDK) 8 or higher
• Java Runtime Environment (JRE) 8 or higher
• Integrated Development Environment (IDE) like IntelliJ IDEA, Eclipse, or VS Code

Configuration

The application is configured for localhost operation:

• Server IP: 127.0.0.1 (localhost)
• RMI Registry Port: 1099
• Hostname: 127.0.0.1

How to Run the RMI System

Step 1: Compile the Code

# Compile all Java files
javac -d . src/**/*.java

Step 2: Start the RMI Registry

# Start RMI registry (in background)
rmiregistry &

Step 3: Start the Server

# Run the server application
java -cp . server.Server

Step 4: Run the Client

# Run the client application
java -cp . client.Client

Alternative: Run in IDE

1. Open the project in your IDE
2. Run Server.java first (right-click → Run)
3. Run Client.java second (right-click → Run)

Expected Output

Server Output

• Server starts successfully
• Creates 4 product instances
• Exports and registers them in RMI registry
• No console output when running successfully

Client Output

Product Name: Product 1
Product Description: Description of Product 1
Product Price: 10.99

Technical Details

RMI Flow

1. Server Initialization:

   • Creates ProductImpl instances with sample data
   • Exports objects using UnicastRemoteObject.exportObject()
   • Registers objects in RMI registry with names "Product1" to "Product4"
   • Sets hostname property for network access

2. Client Operation:

   • Locates RMI registry on localhost:1099
   • Looks up remote objects by registry names
   • Casts retrieved objects to Product interface
   • Invokes remote methods to get product information

Network Configuration

• Registry: Uses default RMI registry port 1099
• Hostname: Configured as 127.0.0.1 for local testing
• Protocol: Uses Java RMI protocol (JRMP)

File Structure

RMI/
├── README.md                    # This documentation
├── RMI.iml                      # IntelliJ IDEA module configuration
└── src/
    ├── Main.java                # Hello world example (not RMI-related)
    ├── client/
    │   ├── Client.java          # RMI Client application
    │   └── Product.java         # Remote interface
    └── server/
        ├── Product.java         # Remote interface (same as client)
        ├── ProductImpl.java     # Implementation of Product interface
        └── Server.java          # RMI Server application

Troubleshooting

Common Issues

1. RMI Registry Not Running:

   java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: 
   java.net.ConnectException: Connection refused
   

   Solution: Start rmiregistry before running the server

2. ClassNotFoundException:

   java.lang.ClassNotFoundException: client.Product
   

   Solution: Ensure proper classpath with -cp . or use IDE's run configuration

3. AlreadyBoundException:

   java.rmi.server.AlreadyBoundException: Product1
   

   Solution: Restart the server to clear registry or use different binding names

4. Security Manager Issues: If using security policies, ensure proper permissions are granted

Debug Tips

1. Check Registry: Verify that objects are properly registered
2. Network: Ensure no firewall blocks port 1099
3. Classpath: Verify all compiled classes are accessible
4. Server Order: Always start server before client

Dependencies

• Java RMI API (built-in with JDK)
• No external dependencies required

Development Notes

• The Main.java file contains a simple hello world example and is not part of the RMI system
• The project uses separate packages for client and server code organization
• All remote methods throw RemoteException as required by RMI specification
• The implementation uses UnicastRemoteObject for remote object export

Educational Purpose

This project serves as a practical demonstration of:

• Remote Method Invocation concepts
• Client-server architecture
• Remote object lifecycle management
• Network programming in Java
• Interface-based remote design patterns

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Created for Advanced Programming Course - Semester 5
University of Ruhuna