This project started as a course assignment for Network Programming but quickly evolved into a full-fledged LAN messaging and file-sharing system — complete with timestamps, file transfer, message logging, and cross-platform support.

My goal was to build a real-time terminal-based chat system that supports multiple users over LAN, allows file sharing, and works seamlessly on both Windows and macOS. The final result is a clean, command-line powered tool that I'm proud to open source.

Project Goals

• Enable real-time multi-user LAN chat
• Allow sending and receiving files between clients
• Implement a command-driven terminal interface
• Log all messages to a file
• Auto-organize received files
• Ensure compatibility on Windows and macOS

Tech Stack

• Language: C++
• Networking: Winsock2 (Windows) and BSD sockets (macOS)
• Threads: std::thread
• Build tools: g++, MinGW, clang++
• Editors: VS Code / Code::Blocks
• Terminal UI: Console output, ANSI color formatting (macOS)

Architecture

The application follows a client-server model. The server handles multiple clients using threads. Messages and files sent from any client are received by the server and broadcast to all other clients.

+-----------+       +-------------+       +-----------+
|  Client A | <---> |   Server    | <---> |  Client B |
+-----------+       +-------------+       +-----------+
       \                                   /
        \--------- File Relay ------------/

Files are broken into chunks and reassembled on the receiving client’s side. A simple protocol using FILE:<filename> and FILE_END markers was used for file transfer.

Key Features

• Real-time messaging over TCP
• File transfer capability
• Timestamped messages
• Chat logs saved to chatlog.txt
• Received files stored in the received/ folder
• Terminal commands: /help, /file, /list, /exit
• Cross-platform: works on Windows and macOS

Challenges Faced

• Handling socket differences between Winsock and BSD sockets
• Ensuring inet_pton() compatibility on Windows (fallback to inet_addr())
• Thread-safe broadcasting and file handling
• Folder creation logic across platforms (_mkdir on Windows, mkdir on macOS)
• Chunked file transfer and recognizing file boundaries with FILE_END

Enhancements I Added

• Server now displays when a user connects or disconnects,
• Received files are auto-organized into a folder,
• All messages (including system messages) are timestamped and logged,
• The /help command shows all supported actions.

Screenshots

What I Learned

This project taught me practical low-level networking — from socket creation to file transfer protocols. I learned how to write threaded applications in C++ and how to make code portable across operating systems. Debugging platform-specific issues also helped me better understand system-level development.

What’s Next

• Add encryption (SSL or AES) for secure communication
• Build a GUI version using Qt or Win32 API
• Implement LAN discovery using UDP broadcast
• Add file transfer progress indicators
• Export chat logs to HTML or Markdown

Source Code

You can find the full project source code on GitHub:
https://github.com/harsh4dev/LanChatroomNP

Thanks for reading! I hope this helps anyone curious about building networked C++ applications. Feel free to test it out or fork it — and message me (over LAN or GitHub 😄)!