Realtime Chat Backend

Backend API for a real-time chat application built with Node.js, Express, MongoDB, and Socket.IO. It handles authentication, user profiles, private messaging, image uploads, and online user presence.

Features

• JWT-based authentication with httpOnly cookies
• User signup, login, logout, and auth verification
• Profile picture upload with Multer + Cloudinary
• Private 1:1 messaging between users
• Message image uploads with Multer + Cloudinary
• Real-time delivery and online presence using Socket.IO
• MongoDB persistence with Mongoose models

Tech Stack

• Node.js
• Express.js
• MongoDB
• Mongoose
• Socket.IO
• Cloudinary
• Multer
• bcryptjs
• JSON Web Token (JWT)
• cookie-parser
• cors
• dotenv
• nodemon

Project Structure

backend/
├── src/
│   ├── controllers/
│   ├── lib/
│   ├── middleware/
│   ├── models/
│   ├── routes/
│   ├── seeds/
│   └── index.js
├── package.json
└── README.md

Setup

1. Install dependencies

cd backend
npm install

2. Create a .env file in the backend root

PORT=5001
MONGO_URI=your_mongodb_connection_string
JWT_SECRET=your_jwt_secret
CLIENT_URL=http://localhost:5173

CLOUDINARY_CLOUD_NAME=your_cloud_name
CLOUDINARY_API_KEY=your_api_key
CLOUDINARY_API_SECRET=your_api_secret

3. Start the development server

npm run dev

API Endpoints

Auth

• POST /api/auth/signup - Register a new user
• POST /api/auth/login - Log in and receive auth cookie
• POST /api/auth/logout - Clear auth cookie
• GET /api/auth/check - Get the currently authenticated user
• PUT /api/auth/update-profile - Update profile picture using multipart/form-data

Messages

• GET /api/messages/users - Get all users except the logged-in user
• GET /api/messages/:id - Get conversation messages with a specific user
• POST /api/messages/send/:id - Send a message to a user using JSON text or multipart/form-data with an image

Request Details

POST /api/auth/signup

Body:

{
  "fullName": "John Doe",
  "email": "john@example.com",
  "password": "password123"
}

POST /api/auth/login

Body:

{
  "email": "john@example.com",
  "password": "password123"
}

PUT /api/auth/update-profile

• Content-Type: multipart/form-data
• Field name: profilePic

POST /api/messages/send/:id

• Content-Type: multipart/form-data
• Text field: text
• Image field: image

Realtime Events

Socket.IO is used for live chat updates and online presence.

Client to Server

• Connection query includes userId

Server to Client

• getOnlineUsers - Sends the list of currently connected user IDs
• newMessage - Broadcasts a newly sent message to the receiver

Middleware

• protectRoute - Verifies JWT cookie and protects private routes
• upload.middleware.js - Handles image uploads with Multer memory storage
• error.middleware.js - Central error handler for upload and server errors

Data Models

User

• email
• fullName
• password
• profilePic
• timestamps

Message

• senderId
• receiverId
• text
• image
• timestamps

Notes

• Authenticated routes require cookies enabled on the client.
• Images are uploaded to Cloudinary; the database stores the returned secure URL.
• The server currently allows image uploads up to 5 MB through Multer.
• Make sure the frontend uses the same field names: profilePic for profile updates and image for chat attachments.

Scripts

• npm run dev - Start the backend in development mode with nodemon