Python Socket Database

A simple client–server database application built using Python sockets.
The server listens for TCP connections, processes structured requests, and stores customer records in a text-based database.

This project was built as a learning exercise to explore TCP socket programming, basic protocol design, and server-side validation in Python.

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Technologies Used

• Python 3
• socket
• socketserver
• Regular expressions (re)
• Threading (for controlled server shutdown)

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Project Structure

python-socket-database/
├── server.py        # TCP server implementation
├── client.py        # Client-side menu interface
├── data.txt         # Initial database file
├── data_out.txt     # Updated database output
└── README.md

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Usage / How to Run

Requirements

• Python 3.9+
• No external libraries required (standard library only)

Step 1: Start the Server

• Open a terminal in the project root directory and run:

python server.py

You should see:

Server is running... listening on localhost:9999

Step 2: Run the Client

• Open another terminal in the same directory and run:

python client.py

This will display the interactive menu.

Step 3: Using the Application

• The client provides a menu-driven interface:

  1. Find Customer
  2. Add Customer
  3. Delete Customer
  4. Update Customer Age
  5. Update Customer Address
  6. Update Customer Phone
  7. Print Report
  8. Update File and Exit

• Input is validated on both client and server sides

• The server processes one request per connection

• Data is stored in memory during runtime

Step 4: Saving and Shutting Down

• To save the database and shut down the server:
  1. Choose option 8 in the client
  2. The server writes data to data_out.txt
  3. The server shuts down gracefully
• After shutdown, the server must be restarted manually:

python server.py

Input Formats

Phone Number

Valid phone numbers must follow this format:

<area-code>-<4 digits> -> xxx-1234

Allowed area codes:

• 394
• 426
• 901
• 514

Examples:

• 514-1234 (valid)
• 426-9876 (valid)
• 5141234 (invalid)
• 999-1234 (invalid)

Notes

• The server accepts one client connection at a time (intentional design)
• Requests are delimited using a newline (\n) as the protocol terminator
• Maximum request size is limited to prevent malformed input
• All communication uses TCP sockets

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Features

• TCP client–server architecture using Python sockets
• Menu-driven client interface
• Supports CRUD-style operations:
  • Create (Add Customer)
  • Read (Find Customer, Print Report)
  • Update (Update Age, Address, Phone)
  • Delete (Remove Customer)
• Custom text-based protocol using | separators and \n as a message delimiter
• Input validation on both client and server sides
• Case-insensitive customer name matching
• In-memory data storage with persistence to a text file on shutdown
• Graceful server shutdown triggered by client command
• Request size limits, timeout handling, and protection against malformed input

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Design Decisions

• Customer name and age are required fields, while address and phone number are optional
• The server is intentionally designed to handle one client session per run
• A simple text-based protocol is used for clarity and learning purposes
• Messages are delimited using a newline (\n) to clearly define request boundaries
• Customer names are treated as case-insensitive for usability
• Data is stored in memory during runtime and written to file only on shutdown
• A menu-driven client interface is used to simplify user interaction

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Limitations

• This project is not intended for production use
• Only one client should connect to the server at a time
• Data persistence relies on plain text files rather than a real database
• No authentication or encryption is implemented
• The server must be restarted manually after shutdown