CS401 Group 4 – Communications System

A Java desktop client–server chat application with role-based access control, WhatsApp-themed GUI, and text-file logging.

Features

• User Authentication: Login via credentials file with ADMIN/GENERAL roles
• Online Presence: Real-time online/offline status tracking
• Private & Group Chat: One-to-one and group conversations
• WhatsApp-themed GUI: Modern, user-friendly interface
• Notifications: Popup notifications for new messages
• Logging & Persistence: All sessions and messages logged to text files

Project Structure

src/
├── common/          # Shared classes (User, Message, Enums)
├── server/          # Server-side code
│   ├── Server.java          # Main server with ClientHandler
│   ├── Authentication.java  # Credential validation
│   ├── ConnectionManager.java # Socket/stream management
│   ├── ChatManager.java     # Chat session management
│   ├── ChatSession.java     # Individual chat sessions
│   ├── Logger.java          # File logging
│   └── UserSession.java     # User session tracking
└── client/          # Client-side code
    ├── AuthGUI.java         # Login window (with main method)
    ├── ClientGUI.java        # Main chat interface
    ├── ClientConnection.java # Network client
    └── Notification.java     # Message notifications

data/
├── credentials.txt  # User credentials (username,password,role)
└── chat_log.txt     # Combined log file (messages and sessions)

Setup Instructions

1. Compile the Project

From the project root directory:

# Create output directory
mkdir -p out

# Compile all Java files
javac -d out -cp . src/common/*.java src/server/*.java src/client/*.java

2. Prepare Data Files

Ensure the data/ directory exists with:

• credentials.txt: Format username,password,role (one per line)
  • Example: alice,alice123,GENERAL
• chat_log.txt: Empty initially (auto-created)
• sessions.txt: Empty initially (auto-created)

3. Run the Server

On the server machine:

# Default port 1234
java -cp out server.Server

# Or specify a port
java -cp out server.Server 1234

The server will:

• Listen for client connections
• Authenticate users from data/credentials.txt
• Route messages between clients
• Log all sessions and messages to text files

4. Run the Client

On each client machine:

java -cp out client.AuthGUI

In the login window:

• Enter username and password (from credentials file)
• Enter server host (IP address or hostname of server machine)
• Enter server port (default: 1234)
• Click Login

Usage

For Users

1. Login: Enter credentials and server address
2. View Contacts: Left panel shows online users
3. Start Chat: Click a user to start a private chat
4. Create Group: Click "New Group", select users, enter group name
5. Send Messages: Type in the input field and click "Send"
6. View History: Previous messages load automatically when opening a chat

For Admins

• Admins see a "View Logs" button (visible only to ADMIN role)
• All other features same as general users

Network Configuration

• Server: Runs on one machine, listens on specified port (default 1234)
• Clients: Connect to server IP/port from their own machines
• Protocol: Uses Java ObjectInputStream/ObjectOutputStream for serialized Message objects

Data File Formats

credentials.txt

username,password,role
alice,alice123,GENERAL
bob,bob123,ADMIN

chat_log.txt (auto-generated, combined file)

MESSAGE|messageID|chatID|senderID|timestamp|content
SESSION|chatID|timestamp|isGroup|participant1,participant2,...|chatName

Troubleshooting

• Connection refused: Check server is running and firewall allows the port
• Login failed: Verify credentials in data/credentials.txt
• User already logged in: Only one session per user allowed
• Messages not appearing: Check server console for errors

Development Notes

• Message class is Serializable for network transmission
• User and ChatSession are also Serializable for session data
• Server uses multi-threaded ClientHandler for each connected client
• Client uses ClientConnection with listener pattern for async message handling
• ConnectionManager creates and manages ObjectInputStream/ObjectOutputStream for each client
• All logs (messages and sessions) are stored in a single chat_log.txt file with MESSAGE| and SESSION| prefixes