Distributed Systems Security

Ahmed Walid

Cross Platform Java server and Client using sockets
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About The Project

This Project consists of two parts:

1. Server: Having two functions:

   • Checking if a string is a palindrome
   • Reversing a string

2. Client: Connects to the server, sends requests, and displays results.

Features

• Configurable Network Settings
• Multithreaded server
• Input Validation
• Error Handling
• Isolated client handling failures (one client error won't affect other clients)
• Clean code

Prerequisites

• Java Development Kit (JDK) 8 or higher
• IntelliJ IDEA IDE (recommended)

Server Implementation

The server listens for client connections and processes string manipulation requests.

Featuring:

1. Configurable Port:

   • The user can choose to use the default port (8888) or specify a custom port (1024-65535).
   • Validates user input to ensure the port is within valid range.

2. Multithreaded Architecture:

   • Each client connection is handled in a separate thread by the ClientHandler class.
   • Allows the server to handle multiple clients simultaneously without blocking.

3. Network Information Display:

   • Shows the server's IP address when started, making it easier for clients whom are on different machine to connect. Note: If the client and the server are on the same machine, use localhost or any loopback IP address actually (127.0.0.0/8)

4. String Manipulation Functions:

   • Palindrome Check: Checks if a string reads the same backward as forward.
     • Returns "1" for palindromes, "0" for non-palindromes.
     • Ignores spaces and isn't case-sensitive for easier use.
   • String Reversal: Reverses the input string.
     • Uses Java's StringBuilder for efficient string manipulation.

5. Error Handling:

   • Socket binding errors
   • Connection acceptance errors (ex: if the port is already in use or if there are firewall restrictions)
   • Client communication errors
   • Invalid input handling

The Server's sequence

1. The server starts and prompts for port configuration.
2. After binding to the port, it displays its IP address and waits for client connections.
3. When a client connects, a new thread is created to handle that client.
4. The handler thread:
   • Reads the function choice (1 or 2)

• Reads the input string
• Processes the request based on the choice
• Sends the result back to the client
• Closes the connection

5. The main server thread continues listening for new connections.

Client Implementation

The client connects to the server, sends requests and displays results.

Featuring:

1. Configurable Connection Settings:

   • Server Address: Use localhost (default) or specify a custom IP address.
   • Server Port: Use default port (5555) or specify a custom port.

2. User Interaction:

   • Clear and formatted output of results.

3. Operation Modes:

   • Palindrome Check: Displays whether the string is a palindrome.
   • String Reversal: Shows the reversed string.

4. Error Handling:

   • Connection failures
   • Invalid server address
   • Invalid port numbers
   • Server communication errors
   • Input validation

Runtime

Server Side:

String Operations Server Setup  
-----------------------------  
Use default port (5555)? (Y/n): y  
Server started on port 8888  
Server IP address: 192.168.57.1
Waiting for clients...  
Client connected: 127.0.0.1  
Client disconnected  

Client Side:

String Operations Client  
------------------------  
Server connection setup:  
Use localhost (default)? (Y/n): n  
Enter server IP address: 127.0.0.1  
Use default port (5555)? (Y/n): y  
Connecting to server at 127.0.0.1:5555...  
Connected to server.  
Choose an operation:  
1. Check if a string is a palindrome  
2. Reverse a string  
Enter your choice (1 or 2): 1  
Enter a string: Ahmed  
Result: "Ahmed" is not a palindrome.  

Contributing

Project's Link: https://github.com/ahmeddwalid/DSSsockets

Any contributions you make are greatly appreciated.

Features to be implemented:

• Security:

  • Adding authentication for client connections
  • Implementing encryption for data transmission
  • Adding server system logs

• User Interface: A long stretch but a GUI possibly?

How to Contribute:

If you'd like to contribute, please follow these steps:

• Fork the repository: Create your own copy of the project.
• Create a branch: git checkout -b feature/your-feature-name
• Make your changes: Implement your contribution.
• Commit your changes: git commit -m "Add your descriptive commit message"
• Push to the branch: git push origin feature/your-feature-name
• Create a pull request: Submit your changes for review.

Contribution Guidelines

• Write clear and concise commit messages.
• Provide detailed explanations in your pull requests.
• Be respectful and considerate of other contributors.

Thank you for your contributions!

License

This project is distributed under the Apache 2.0 license. See LICENSE.txt for more information.

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