chat-app

Cross-platform TLS chat app built with Boost.Asio (C++20).

Overview

This project provides:

• chat_server: async TLS chat server
• chat_client: console TLS client with auto-reconnect
• Length-prefixed JSON protocol (4-byte big-endian length + JSON payload)
• Optional Python stress test for load testing

Features

• TLS-encrypted client/server communication
• Broadcast chat messages
• Private/direct messages
• Join/leave notifications
• Multi-threaded server io_context execution
• Automatic client reconnect on disconnect

Repository layout

• server/ – server implementation
• client/ – console client and networking
• common/ – shared protocol and TCP framing utilities
• certs/ – TLS cert and key (server.crt, server.key)
• scripts/stress_test.py – asyncio-based stress/load tool

Prerequisites

• CMake >= 3.16
• C++20 compiler (g++/clang++)
• Boost (System)
• OpenSSL
• POSIX Threads
• nlohmann/json headers

Typical Ubuntu packages:

sudo apt-get update
sudo apt-get install -y build-essential cmake libboost-system-dev libssl-dev nlohmann-json3-dev

Build

From repository root:

cmake -S . -B build
cmake --build build -j

This produces:

• build/chat_server
• build/chat_client

Run

Open two terminals.

1) Start server

cd build
./chat_server

2) Start client

cd build
./chat_client <username>

If username is omitted, it defaults to Test-Client.

Client input format

The console client expects each line in this format:

<type>|<from>|<to>|<text>

Where <type> is one of:

• Join
• Chat
• Private
• Leave

Examples:

Chat|alice||Hello everyone!
Private|alice|bob|Hi Bob
Leave|alice||

Note: The client sends Join automatically right after TLS handshake, so manual Join is usually unnecessary.

Notes

• TLS certificate/key paths are currently expected relative to running binaries from build/.
• CMake also copies certs/ into build/certs, but runtime code currently loads from ../certs/....