Chat Application

A feature-rich terminal-based chat application with support for one-to-one messaging, group chats, chat history, and continuous chat mode.

Features

✨ Authentication

• User registration and login
• Secure password hashing (SHA-256)
• Session-based authentication with tokens

💬 Private Messaging

• Send direct messages to users
• Continuous chat mode for seamless conversations
• Real-time message delivery
• Chat history saved automatically

👥 Group Chat

• Create and manage groups
• Join/leave groups
• Send messages to all group members
• Group chat history

📝 Chat History

• Automatic saving of all conversations
• History stored in text files
• Organized by conversation

🎨 Interactive CLI

• Colorful terminal interface
• Real-time message notifications
• Multiple chat modes
• Help system

Installation

1. Clone or download the repository
2. Navigate to the project directory:

   cd chat-app

3. Create a virtual environment (optional but recommended):

   python -m venv .venv
   source .venv/bin/activate  # On Linux/Mac
   # or
   .venv\Scripts\activate  # On Windows

Running the Application

Start the Server

cd /home/tej/chat-app
PYTHONPATH=/home/tej/chat-app python server/server.py

The server will start listening on port 5000.

Start the Client

In a new terminal:

cd /home/tej/chat-app
PYTHONPATH=/home/tej/chat-app python client/client.py

You can run multiple clients to simulate different users.

Usage Guide

Authentication Commands

Register a new account:

> register
Username: alice
Password: mypassword

Login:

> login
Username: alice
Password: mypassword

Private Messaging

Send a single message:

> send bob Hello Bob!

Enter continuous chat mode with a user:

> chat bob
@bob > Hello!
@bob > How are you?
@bob > /exit

In continuous chat mode:

• Just type your message and press Enter
• Type /exit to leave continuous chat mode
• The prompt shows @username > to indicate you're chatting with that user

Group Chat

Create a new group:

> create developers

Join an existing group:

> join developers

Send a message to a group:

> gsend developers Hello everyone!

Enter continuous group chat:

> gchat developers
#developers > Good morning team!
#developers > Anyone available?
#developers > /exit

List your groups:

> groups

View group members:

> members developers

Leave a group:

> leave developers

Other Commands

Show help:

> help

Exit the application:

> quit

or

> exit

Chat History

All conversations are automatically saved to text files in the chat_history/ directory:

• One-to-one chats: chat_history/user1:user2.txt
• Group chats: chat_history/group_groupname.txt

Example history file content:

Chat History: alice and bob
============================================================

[2026-01-28 14:30:15] alice -> bob
  Hello Bob!

[2026-01-28 14:30:22] bob -> alice
  Hi Alice!

Architecture

Project Structure

chat-app/
├── client/
│   └── client.py          # Client application
├── server/
│   ├── server.py          # Main server
│   ├── auth.py            # Authentication logic
│   ├── session.py         # Session management
│   ├── router.py          # Message routing
│   ├── groups.py          # Group management
│   └── history.py         # Chat history storage
├── shared/
│   └── protocol.py        # Communication protocol
├── chat_history/          # Saved chat logs (auto-created)
├── requirements.txt       # Python dependencies
├── DATA_STRUCTURES.md     # Data structures documentation
└── README.md             # This file

Key Components

• Server: Handles multiple clients, routes messages, manages authentication
• Client: Terminal UI for user interaction
• Protocol: JSON-based message format
• History: Persistent storage of all conversations
• Groups: Multi-user chat rooms

Data Structures

For detailed documentation of all data structures used in the application, see DATA_STRUCTURES.md.

Example Session

User Alice

$ python client/client.py
╔═══════════════════════════════════════╗
║     Chat Application v2.0             ║
║  Now with Groups & Continuous Chat!   ║
╚═══════════════════════════════════════╝
✓ Connected to server

Guest > register
Username: alice
Password: ***
✓ Registration successful! You can now login.

Guest > login
Username: alice
Password: ***
✓ Logged in successfully!

alice > create developers
✓ Group 'developers' created successfully!

alice > chat bob
Entered chat with bob. Type /exit to leave.
@bob > Hey Bob, want to join the developers group?
[14:35:10] You: Hey Bob, want to join the developers group?
[14:35:23] bob: Sure! How do I join?
@bob > Just type: join developers
[14:35:30] You: Just type: join developers
@bob > /exit
Exited continuous chat mode

alice > gchat developers
Entered group chat: developers. Type /exit to leave.
#developers > Welcome to the team!
[14:36:15] You: Welcome to the team!
[14:36:20] [developers] bob: Thanks! Happy to be here.
#developers > /exit

User Bob

$ python client/client.py
✓ Connected to server

Guest > register
Username: bob
Password: ***

Guest > login
Username: bob
Password: ***
✓ Logged in successfully!

[14:35:10] alice: Hey Bob, want to join the developers group?

bob > send alice Sure! How do I join?

[14:35:30] alice: Just type: join developers

bob > join developers
✓ Joined group 'developers'!

[14:36:15] [developers] alice: Welcome to the team!

bob > gsend developers Thanks! Happy to be here.

Protocol

The application uses a JSON-based protocol over TCP sockets. Messages are newline-delimited JSON objects.

Message Types

• AUTH: Authentication (register, login)
• CHAT: Private messages
• GROUP: Group operations and messages
• SYSTEM: Server responses and notifications

For complete protocol documentation, see DATA_STRUCTURES.md.

Security Note

⚠️ This is a demonstration project. The current implementation:

• Uses SHA-256 for password hashing (single hash, no salt)
• Transmits messages in plaintext
• Stores passwords in memory

For production use, you should:

• Use proper password hashing (bcrypt, argon2)
• Implement TLS/SSL for encrypted communication
• Use a proper database for persistence
• Add input validation and sanitization
• Implement rate limiting
• Add proper error handling

Future Enhancements

• File transfer support
• End-to-end encryption
• Message read receipts
• User presence indicators
• Database persistence (SQLite/PostgreSQL)
• Web-based client
• Voice/video chat
• Message search functionality
• User profiles and avatars

License

This project is for educational purposes.

Contributing

Feel free to fork and enhance the project!