Advanced Communication

GraphQL

GraphQL is a query language for APIs that allows clients to request exactly the data they need. Use express-graphql and graphql packages to add GraphQL to your Express server.

// Install: npm install express-graphql graphql

const { buildSchema } = require('graphql');
const { graphqlHTTP } = require('express-graphql');

// Define schema
const schema = buildSchema(`
  type User {
    id: ID!
    name: String!
    email: String!
    posts: [Post]
  }

  type Post {
    id: ID!
    title: String!
    content: String
  }

  type Query {
    user(id: ID!): User
    users: [User]
    posts: [Post]
  }

  type Mutation {
    createUser(name: String!, email: String!): User
    createPost(title: String!, content: String): Post
  }
`);

// Resolvers
const root = {
  users: () => [
    { id: '1', name: 'Alice', email: 'alice@example.com' }
  ],
  user: ({ id }) => ({
    id, name: 'Alice', email: 'alice@example.com'
  })
};

app.use('/graphql', graphqlHTTP({
  schema,
  rootValue: root,
  graphiql: true  // Enable GraphQL IDE
}));

Socket.IO

Socket.IO enables real-time, bidirectional event-based communication between web clients and servers.

// Install: npm install socket.io

const http = require('http');
const { Server } = require('socket.io');

const server = http.createServer(app);
const io = new Server(server, {
  cors: { origin: '*' }
});

io.on('connection', (socket) => {
  console.log('A user connected:', socket.id);

  // Listen for events
  socket.on('chat message', (msg) => {
    console.log('Message received:', msg);
    // Broadcast to all connected clients
    io.emit('chat message', {
      user: socket.id,
      message: msg,
      timestamp: new Date()
    });
  });

  socket.on('join room', (room) => {
    socket.join(room);
    socket.to(room).emit('notification', `${socket.id} joined ${room}`);
  });

  socket.on('disconnect', () => {
    console.log('User disconnected:', socket.id);
  });
});

server.listen(3000, () => {
  console.log('Socket.IO server running on port 3000');
});

Client-Side Socket.IO

const socket = io('http://localhost:3000');

// Send message
socket.emit('chat message', 'Hello everyone!');

// Listen for messages
socket.on('chat message', (data) => {
  console.log(`${data.user}: ${data.message}`);
});

WebSockets (Native)

Node.js also supports raw WebSockets via the ws library for lower-level control.

// Install: npm install ws

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws) => {
  console.log('WebSocket client connected');

  ws.on('message', (message) => {
    console.log('Received:', message.toString());

    // Broadcast to all clients
    wss.clients.forEach((client) => {
      if (client.readyState === WebSocket.OPEN) {
        client.send(`Echo: ${message}`);
      }
    });
  });

  ws.send('Welcome to the WebSocket server!');
});

Polling vs WebSockets