WebSockets vs. Server-Sent Events (SSE) vs. WebRTC

In today’s fast-paced digital world, real-time communication is a key component of many web applications. Whether it's live messaging, notifications, or video calls, delivering instant updates and responses can make or break user experience. To achieve this, web developers have a few tools at their disposal: WebSockets, Server-Sent Events (SSE), and WebRTC. Each has its own strengths and ideal use cases, but which one is the best fit for your project?

In this blog, we’ll break down the differences between these three technologies, give you some easy-to-understand examples, and help you choose the right one for your next web app.

1. WebSockets: Two-Way Communication for Real-Time Interactions

   WebSockets are all about speed and two-way communication. Unlike regular HTTP requests that only allow the client (browser) to request data from the server, WebSockets let both the client and the server send messages to each other as soon as they have something to say. This makes WebSockets perfect for scenarios where fast, back-and-forth interaction is needed, like:

   • Real-time chat applications

   • Online multiplayer games

   • Collaborative tools (like Google Docs)

Why Use WebSockets?

• Full-duplex communication: Both client and server can send messages anytime.

• Low-latency: Great for real-time data transfer where speed is crucial.

Client Side Code

        // Create a new WebSocket connection
        const socket = new WebSocket('wss://example.com/socket');

        // When the connection opens, send a message to the server
        socket.addEventListener('open', () => {
          console.log('Connected to the server');
          socket.send('Hello, Server!');
        });

        // Listen for messages from the server
        socket.addEventListener('message', (event) => {
          console.log('Message from server:', event.data);
        });

        // Handle connection closure
        socket.addEventListener('close', () => {
          console.log('Connection closed');
        });

Server Side Code

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

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

          // Respond to messages from the client
          ws.on('message', message => {
            console.log('Received:', message);
            ws.send('Hello, Client!');
          });

          // Handle connection closure
          ws.on('close', () => {
            console.log('Client disconnected');
          });
        });

2. Server-Sent Events (SSE): Simple, One-Way Updates

   Server-Sent Events (SSE) are great when you only need the server to send updates to the client without expecting the client to send much back. Think of it as the server constantly pushing information to the browser. This is perfect for live updates that don’t need to go both ways, like:

   • Real-time news feeds

   • Live sports scores

   • Stock price updates

Why Use SSE?

• One-way communication: The server pushes data to the client.

• Easy to implement: SSE uses standard HTTP, making it simple to set up.

• Automatic reconnection: If the connection drops, the browser will automatically try to reconnect.

Client Side Code

    // Set up an EventSource to receive updates from the server
    const eventSource = new EventSource('/events');

    // Listen for incoming messages
    eventSource.onmessage = (event) => {
      console.log('New message from server:', event.data);
    };

    // Handle errors (e.g., if the connection is lost)
    eventSource.onerror = (error) => {
      console.error('Error with SSE:', error);
    };

Server Side Code

    const http = require('http');

    http.createServer((req, res) => {
      if (req.url === '/events') {
        // Set headers to enable SSE
        res.writeHead(200, {
          'Content-Type': 'text/event-stream',
          'Cache-Control': 'no-cache',
          'Connection': 'keep-alive',
        });

        // Send an update every second
        setInterval(() => {
          res.write(`data: ${new Date().toLocaleTimeString()}\n\n`);
        }, 1000);
      }
    }).listen(8080, () => console.log('SSE server running on port 8080'));

3. WebRTC: Peer-to-Peer Magic for Media and Data

   WebRTC is a little different from WebSockets and SSE. It’s designed for peer-to-peer (P2P) communication, meaning you can connect two users directly without needing a central server to handle the data. This makes it the go-to option for things like:

   • Video calls (e.g., Zoom, Google Meet)

   • File sharing between users

   • Multiplayer games where players interact directly

Why Use WebRTC?

• Peer-to-peer connections: Allows users to communicate directly, reducing server load.

• Low-latency media streaming: Ideal for video, audio, and real-time data sharing.

• Secure: WebRTC encrypts data by default.

Client Side Code

    // Create RTCPeerConnection for both peers
    const peer1 = new RTCPeerConnection();
    const peer2 = new RTCPeerConnection();

    // Create a data channel on peer1
    const dataChannel = peer1.createDataChannel('chat');
    dataChannel.onopen = () => console.log('Data channel open');
    dataChannel.onmessage = (event) => console.log('Message from Peer 2:', event.data);

    // Exchange offer and answer to establish connection
    peer1.createOffer().then(offer => {
      peer1.setLocalDescription(offer);
      peer2.setRemoteDescription(offer);

      peer2.createAnswer().then(answer => {
        peer2.setLocalDescription(answer);
        peer1.setRemoteDescription(answer);
      });
    });

    // Send a message once the connection is established
    dataChannel.send('Hello Peer 2!');

Comparison at a Glance:

(Retries built-in) | Requires signalling server |

Summary (Which one should you choose)

• Go with WebSockets if you need fast, two-way communication like in a live chat or online game. It’s the best option for frequent back-and-forth messaging.

• Use SSE if you just need to push real-time updates from the server to the client, like live scores or stock prices. SSE is simple, reliable, and easy to set up.

• Pick WebRTC if your application involves peer-to-peer communication, such as video conferencing or file sharing. WebRTC is optimized for low-latency, real-time media sharing.

With this breakdown, you’re now equipped to decide which real-time communication tool works best for your project. Whether you're pushing live updates, building a chat app, or setting up a video call, knowing the strengths of WebSockets, SSE, and WebRTC will make a huge difference in your app's performance and scalability.

Happy coding!