ChatApp

A lightweight, database‑backed, two-user private chat application with real-time messaging, built using PHP, MySQL, WebSockets, and Docker.

Disclaimer: This academic prototype is not production‑ready. Messages are stored in plaintext in MySQL; only passwords are hashed via PHP’s password_hash.

Table of Contents

• ChatApp
  • Table of Contents
  • Prerequisites
  • Setup & Run
  • Project Structure
  • Database Schema
  • REST API Endpoints
  • Frontend
  • WebSocket Server
  • Stopping & Teardown
  • License

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Prerequisites

• Docker (Engine or Desktop)
• Docker Compose
• Familiarity with PHP & MySQL

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Setup & Run

1. Clone repository

   git clone https://github.com/your-username/ChatApp.git
   cd ChatApp/ChatApp - Applicazione Finita

2. Build and launch

   docker-compose up --build

3. Access the services

   • Web UI (static pages): http://localhost (port 80)
   • WebSocket endpoint: ws://localhost:8080
   • MySQL: localhost:3306 (credentials defined in db/init.sql)

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Project Structure

ChatApp - Applicazione Finita/
├── docker-compose.yml           # defines db, web, ws-server services
├── db/
│   ├── Dockerfile              # MySQL 8.0 setup, timezone Europe/Rome
│   └── init.sql                # schema: users, chats, messages, tokens
├── web/
│   ├── Dockerfile              # PHP 8.2 + Apache configuration
│   ├── apache.conf             # vhost & error pages
│   └── files/
│       ├── index.php           # SPA entry point
│       ├── login.php           # login UI
│       ├── register.php        # register UI
│       ├── logout.php          # logout handler
│       ├── errors/             # HTTP error pages
│       │   ├── 403.html
│       │   └── 404.html
│       └── backend/            # REST API handlers
│           ├── db.php
│           ├── e_register.php
│           ├── e_login.php
│           ├── check_user_existence.php
│           └── get_chats.php
└── ws-server/
    ├── Dockerfile              # PHP 8.1 CLI + sockets extension
    └── files/
        ├── db.php              # PDO MySQL connection
        └── ws.php              # WebSocket server logic

• db/: Initializes chat_app database in MySQL container.
• web/: Serves REST API and frontend via Apache+PHP.
• ws-server/: Handles WebSocket connections for real-time messaging.

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Database Schema

Database: chat_app

Table	Columns	Notes
users	id PK, username UNIQUE, password	Password hashed via password_hash
chats	id PK, user1_id FK, user2_id FK,participant_pair GENERATED UNIQUE	participant_pair enforces unique pairs
messages	id PK, chat_id FK, sender_id FK, content, sent_at TIMESTAMP
tokens	id PK, user_id FK, token	WS authentication token

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REST API Endpoints

All under web/files/backend/:

• POST /e_register.php Request: { username, password } → Creates new user.

• POST /e_login.php Request: { username, password } → Starts PHP session, issues WS token.

• GET /check_user_existence.php?username=<name> Response: { status: success|error }.

• GET /get_chats.php Response: JSON array of chats for user. The user_id is taken from the $_SESSION

The other PHP pages perform calls to these endpoints.

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Frontend

Located in web/files:

• register.php and login.php handle user onboarding.
• index.php provides the live chat interface, displays all users' chats and manages the connection to the WebSocket server.
• Static assets (favicon.ico, default-avatar.jpg, imgs) are embedded or referenced.

The frontend uses JavaScript in index.php to:

1. Call REST API for login/registration and fetching chats.

2. Establish a WebSocket connection:

   let ws = new WebSocket('ws://' + location.hostname + ':8082');

3. Send autentication request:

// Instruction for autentication
      ws.onopen = () => {
          // Trying autentication on opened connection
          setTimeout(() => {
              ws.send(JSON.stringify({
                  type: 'auth',
                  user_id: user_id,
                  token: token
              }));
          }, 100);
          // Some other things
      };

4. Send/receive messages in JSON frames.

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WebSocket Server

In ws-server/files/ws.php:

1. Setup: Binds TCP socket on 0.0.0.0:8080.
2. Handshake: Validates user_id and token against tokens table.
3. Loop: Uses socket_select() to manage each socket in a always running loop.
4. Frame Handling: Helpers readFrame()/sendFrame() to easily compose and receive new frames.

---

Stopping & Teardown

docker-compose down -v

This stops all containers and removes associated volumes.

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License

Released under the MIT License. Feel free to fork, modify, and learn from this project.