PyChat - LAN Based Secure Chat Room

A secure, encrypted group chat application designed for local area networks (LAN) built in Python with real-time messaging, file sharing, and comprehensive admin controls.

🔐 Features

• LAN-Optimized: Designed specifically for local area network communication
• End-to-End Encryption: All messages and files are encrypted using Fernet symmetric encryption
• Group Management: Create and join chat groups with admin approval system
• Real-time Messaging: Instant message delivery to all online group members
• File Sharing: Securely share files with all group members
• Admin Controls:
  • Approve/deny join requests
  • Kick members from groups
  • Transfer admin privileges
  • View member lists and pending requests
• Multi-threaded Architecture: Concurrent handling of multiple clients
• Cross-platform: Works on Windows, macOS, and Linux

🚀 Quick Start

Prerequisites

• Python 3.7 or higher
• Required packages: cryptography

Installation

1. Clone the repository:

git clone https://github.com/m-ahmad3/PyChat-LAN-Secure.git
cd Pychat-LAN-Secure

2. Install dependencies:

pip install cryptography

Usage

1. Start the server:

python Server.py <IP> <Port>
# Example for LAN:
python Server.py 192.168.1.100 8000
# Or for local testing:
python Server.py localhost 8000

2. Connect clients:

python Client.py <IP> <Port>
# Example for LAN:
python Client.py 192.168.1.100 8000
# Or for local testing:
python Client.py localhost 8000

3. Create or join a group:
   • Enter your username when prompted
   • Enter the group name (creates new group if it doesn't exist)
   • First user becomes the admin automatically

📋 Commands

Once connected, use these commands:

Command	Description	Admin Only
/1	View join requests	✅
/2	Approve join requests	✅
/3	Disconnect from chat	❌
/4	View all group members	❌
/5	View online members	❌
/6	Transfer admin privileges	✅
/7	Check current group admin	❌
/8	Kick a member	✅
/9	Share a file	❌

Type any other text to send a regular message to the group.

🏗️ Architecture

Server Components

• Group Management: Handles group creation, member management, and permissions
• Encryption Layer: Encrypts/decrypts all communications using Fernet
• Multi-threading: Each client connection runs in a separate thread
• File Transfer: Secure file sharing with automatic cleanup

Client Components

• Dual Threading: Separate threads for sending and receiving messages
• State Management: Tracks connection status and user permissions
• Interactive CLI: User-friendly command-line interface

🔧 Technical Details

Security

• Uses Fernet (AES 128 encryption) for symmetric encryption
• Encryption key is generated server-side and shared during handshake
• All messages, files, and commands are encrypted in transit
• No data persistence - all information is stored in memory

Network Protocol

• TCP socket communication
• Custom protocol with length-prefixed encrypted messages
• Automatic reconnection handling for network interruptions

File Transfer

• Files are encrypted before transmission
• Temporary server-side storage with automatic cleanup
• Supports any file type and size (within memory limits)

🐛 Known Issues

• Large file transfers may consume significant memory
• Server shutdown requires manual process termination
• No message history persistence between sessions