CollaborativeNotepad

CollaborativeNotepad is a concurrent Server-Client application that allows for the collaborative editing of text files in real-time. Built entirely in C, it provides a terminal-based user interface and ensures data consistency across multiple users.

Features

• Real-Time Collaborative Editing: Up to two clients can edit the same document simultaneously while viewing each other's cursor positions in real-time.
• Centralized Architecture: The server acts as the Single Source of Truth, ensuring no discrepancies exist between the document versions visible to different clients[.
• User Authentication: Secure login and registration system with enforced password complexity (minimum 8 characters, requiring at least one uppercase letter, one lowercase letter, and one number).
• File Management: Users can create, download, delete, and list available files directly from the terminal[.
• Terminal UI: A clean, multi-window interface built with ncurses that separates the document view from the command input.

Tech Stack

• Language: C (POSIX standard)
• Networking: TCP/IP Sockets for reliable data transmission and data integrity
• Concurrency: POSIX Threads (Pthreads) utilizing a Thread-per-Connection model
• Synchronization: Mutexes to prevent race conditions during concurrent file access
• Database: SQLite3 for persistent storage of user credentials and document content
• UI: ncurses library for terminal rendering

Compilation and Execution

Prerequisites

Ensure you have gcc, sqlite3, and ncurses installed on your Linux environment.

Server

Compile the server: gcc server.c -o server -lsqlite3 -pthread

Run the server: ./server (The server runs on port 6060 by default).

Client

Compile the client: gcc client.c -o client -lncurses

Run the client: ./client <server_ip_address> 6060

Usage Commands

Once the client is running, you can interact with the application using the following commands:

• register <username> <password> <confirm_password>: Register a new account
• login <username> <password>: Authenticate your session
• create <filename>: Create a new text file
• files: List all files stored on the server
• edit <filename>: Open a file in collaborative edit mode
• download <filename> <optional_path>: Download a file from the server to your local machine

Edit Mode Commands:

• insert <position> <text>: Insert text at a specific position (or at the current cursor if omitted)
• delete <position> <length>: Delete characters
• save: Save the current state to the database
• exit_edit: Exit the editing session