2. Sending and Receiving Events

A. Client → Server (socket.emit from client)

Client:

// frontend.js
socket.emit("chatMessage", { text: "Hello server!" });

Server:

// server.js
socket.on("chatMessage", (data) => {
  console.log("Received from client:", data);
});

• Who receives? Server only.
• Use case: User sends a chat message to the server.

B. Server → Client (socket.emit from server)

Server:

socket.emit("welcome", "Hello, this is a private welcome message!");

Client:

socket.on("welcome", (msg) => {
  console.log(msg);
});

• Who receives? Only that connected client.
• Use case: Sending a private welcome message after connecting.

C. Server → All Clients (io.emit)

Server:

io.emit("announcement", "Server will restart in 5 minutes.");

Client:

socket.on("announcement", (msg) => {
  console.log(msg);
});

• Who receives? Every connected client.
• Use case: Public announcements.

D. Server → All Except Sender (socket.broadcast.emit)

Server:

socket.broadcast.emit("userJoined", `${socket.id} joined the chat.`);

Client:

socket.on("userJoined", (msg) => {
  console.log(msg);
});

• Who receives? All clients except the sender.
• Use case: Notify others when a new user joins.

E. Rooms: Joining & Leaving

Server:

socket.join("room1"); // Join
socket.leave("room1"); // Leave

• Use case: Group chats, game lobbies.

F. Emit to a Room

Server:

io.to("room1").emit("roomMessage", "Hello Room 1!");

Client:

socket.on("roomMessage", (msg) => {
  console.log(msg);
});

• Who receives? Everyone in room1.
• Use case: Chat messages for a specific group.

G. Emit to a Room Except Sender

Server:

socket.to("room1").emit("roomMessage", "Someone else says hello!");

• Who receives? Everyone in room1 except sender.
• Use case: Prevent echoing messages back to sender.

H. Private Messaging via Socket ID

Server:

io.to("some-socket-id").emit("privateMessage", "Hey! Just for you.");

Client:

socket.on("privateMessage", (msg) => {
  console.log(msg);
});

• Who receives? The client with that socket ID.
• Use case: One-to-one chat.

I. Listening for Events

Server:

socket.on("typing", () => {
  console.log(`${socket.id} is typing...`);
});

Client:

socket.on("userTyping", (user) => {
  console.log(`${user} is typing...`);
});

• Use case: Typing indicators.

3. Quick Reference Table

Pro Tip: Always namespace your events and avoid generic names like message to prevent conflicts in large apps.

Installation

# Clone the repository
$ git clone https://github.com/ExploitEngineer/secure-todo-app.git

# Navigate into the project directory
$ cd secure-todo-app

# Install backend dependencies
$ cd server
$ npm install

# Setup SQLite DB (optional: seed data)
$ npx sequelize-cli db:migrate
$ cd ..

# Install frontend dependencies
$ cd client
$ npm install

Running the App

Start Backend

cd server
npm run dev

Start Frontend

cd client
npm start

Folder Structure

secure-todo-app/
├── client/          # React frontend
│   └── ...
├── server/          # Express backend
│   ├── controllers/
│   ├── middleware/
│   ├── models/
│   ├── routes/
│   └── ...
└── README.md

Security Highlights

• Passwords hashed with bcrypt
• JWT-based session management
• Protected routes on both frontend & backend
• Secure API design practices

License

This project is open-source and available under the MIT License.

Made with ❤️ by ExploitEngineer

This project is a full-stack Travel Website featuring a dynamic frontend built with React.js and a robust backend powered by Node.js, Express, and MongoDB. It provides a seamless experience for users to explore destinations, book trips, and manage bookings. The application is designed with a modern, responsive UI and secure API endpoints for effici