C++23 P2P Chat System

A modern peer-to-peer chat application built with C++23, featuring end-to-end encryption, colored terminal output, and vi-like CLI interaction.

Features

• Decentralized P2P Architecture: Direct peer-to-peer connections without central servers
• Cryptographic Security: ECDSA key pairs, digital signatures, and encryption via OpenSSL
• Modern C++23: Leverages latest language features for clean, efficient code
• Colored Terminal UI: Beautiful colored output with lambda (λ) prompt
• Vi-like Interface: Replxx library provides vi keybindings and command history
• Comprehensive Testing: 55 unit tests covering all major components
• Thread-Safe Operations: Concurrent peer management and network operations
• Persistent State: Save and restore peer lists between sessions

Requirements

• C++23 compatible compiler (GCC 13+, Clang 16+, or MSVC 2022+)
• CMake 3.20 or higher
• Boost 1.75+ (system, thread, filesystem, chrono, program_options)
• OpenSSL development libraries
• Internet connection (for automatic dependency fetching)

Project Structure

CppP2PChat/
├── Include/          # Header files
├── Source/           # Implementation files
├── Tests/            # Unit tests
├── external/         # Third-party headers (rang.hpp)
├── build/            # Build output directory
├── CMakeLists.txt    # Build configuration
├── b                 # Quick build script
└── r                 # Run script with tmux

Building

Quick Build

./b  # Uses the included build script

Manual Build

mkdir -p build
cd build
cmake ..
make -j$(nproc)

Build Options

cmake -DBUILD_TESTS=OFF ..    # Build without tests
cmake -DCMAKE_BUILD_TYPE=Debug ..  # Debug build

All executables are output to build/Bin/ directory.

Testing

Run all 55 unit tests:

cd build
ctest --verbose

Run specific test suite:

./Bin/TestCrypto       # Cryptography tests
./Bin/TestMessage      # Message protocol tests
./Bin/TestPeerManager  # Peer management tests
./Bin/TestNetwork      # Network layer tests
./Bin/TestCliInterface # CLI interface tests

Usage

Basic Usage

./build/Bin/p2pchat

Advanced Options

./build/Bin/p2pchat --port 8081 --connect localhost:8080 --peers-file mypeers.txt

Demo Script

Run two peers in a tmux session:

./r  # Starts two peers that auto-connect

Commands

Connection Management

• connect <address> <port> - Connect to a peer
• disconnect <peer_id> - Disconnect from a peer
• list - Show all peers and connection status

Messaging

• send <peer_id> <message> - Send to specific peer
• broadcast <message> - Send to all connected peers

Information

• info - Display local peer information
• help - Show all available commands
• quit or exit - Exit the application

Vi Mode Navigation

• ESC - Enter normal mode
• h,j,k,l - Vi movement keys
• i - Return to insert mode
• Ctrl+W - Delete word
• Ctrl+U - Delete to beginning of line

Architecture

Core Components

• CryptoManager - Handles ECDSA key pairs, signatures, and encryption
• NetworkManager - Manages TCP connections with Boost.Asio
• PeerManager - Thread-safe peer tracking and persistence
• Message - Protocol implementation with serialization
• CLIInterface - Colored terminal UI with vi-like input

Message Protocol

[Type:1][PayloadSize:4][Timestamp:8][Payload:N]

Supported message types:

• TEXT (0x01) - Chat messages
• HANDSHAKE (0x02) - Peer introduction
• PEER_LIST (0x03) - Share known peers
• PING (0x04) - Keepalive
• PONG (0x05) - Keepalive response

Security

• Key Generation: Each peer generates ECDSA keypair on startup
• Peer Identity: IDs derived from public key SHA-256 hash
• Message Signing: All messages can be digitally signed
• Encryption: Point-to-point encryption using ECDH shared secrets
• No Central Authority: Fully decentralized trust model

Dependencies

External dependencies (auto-fetched):

• Google Test - Unit testing framework
• Replxx - Vi-like CLI library
• rang - Terminal color library

System dependencies:

• Boost libraries
• OpenSSL
• pthreads

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Add tests for new functionality
4. Ensure all tests pass (ctest)
5. Commit your changes (git commit -m 'Add some AmazingFeature')
6. Push to the branch (git push origin feature/AmazingFeature)
7. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Boost.Asio for excellent async networking
• OpenSSL for cryptographic primitives
• Google Test for testing framework
• Replxx for vi-like CLI experience
• rang for beautiful terminal colors