Streaming Options for UI: SSE, WebSocket, and Long Poll

When building real-time applications, choosing the right streaming technology is crucial for delivering a seamless user experience. In this blog post, we’ll explore different streaming options for UI development, compare their features, and provide guidance on when to use each technology.

Server-Sent Events (SSE)

Server-Sent Events (SSE) is a simple and efficient protocol for one-way server-to-client communication. It allows the server to push data to the client over a single HTTP connection.

Example:

// Client-side JavaScript
const eventSource = new EventSource('/stream');

eventSource.onmessage = (event) => {
  console.log('Received:', event.data);
};

// Server-side (Node.js with Express)
app.get('/stream', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive'
  });

  const sendEvent = () => {
    res.write(`data: ${new Date().toLocaleTimeString()}\n\n`);
  };

  const intervalId = setInterval(sendEvent, 1000);

  req.on('close', () => {
    clearInterval(intervalId);
  });
});

Pros:

• Simple to implement
• Works over standard HTTP
• Automatic reconnection

Cons:

• One-way communication only
• Limited browser support for older versions

WebSocket

WebSocket provides full-duplex, bidirectional communication between client and server over a single TCP connection.

Example:

// Client-side JavaScript
const socket = new WebSocket('ws://localhost:8080');

socket.onopen = () => {
  console.log('Connected to WebSocket');
  socket.send('Hello, server!');
};

socket.onmessage = (event) => {
  console.log('Received:', event.data);
};

// Server-side (Node.js with ws library)
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws) => {
  ws.on('message', (message) => {
    console.log('Received:', message);
    ws.send('Hello, client!');
  });
});

Pros:

• Full-duplex communication
• Low latency
• Supports binary data

Cons:

• Requires WebSocket-specific server setup
• May be blocked by some firewalls

Long Polling

Long polling is a technique where the client repeatedly polls the server for new information, and the server holds the request open until new data is available.

Example:

Long polling is a technique where the client repeatedly polls the server for new information, and the server holds the request open until new data is available.

Example:

// Client-side JavaScript
function longPoll() {
  fetch('/poll')
    .then(response => response.json())
    .then(data => {
      console.log('Received:', data);
      longPoll(); // Immediately start the next long poll
    })
    .catch(error => {
      console.error('Error:', error);
      setTimeout(longPoll, 1000); // Retry after 1 second on error
    });
}

longPoll();

// Server-side (Node.js with Express)
let clients = [];

app.get('/poll', (req, res) => {
  clients.push(res);
  
  req.on('close', () => {
    clients = clients.filter(client => client !== res);
  });
});

function broadcast(message) {
  clients.forEach(client => {
    client.json(message);
    clients = clients.filter(c => c !== client);
  });
}

// Example: Broadcast a message every 5 seconds
setInterval(() => {
  broadcast({ time: new Date().toLocaleTimeString() });
}, 5000);

Pros:

• Works in all browsers
• Simpler server implementation

Cons:

• Higher latency
• More server resources used

Comparison and Use Cases

When to use SSE:

• For real-time updates where server-to-client communication is sufficient
• When you need a simple implementation that works over standard HTTP
• For applications that require automatic reconnection

When to use WebSocket:

• For applications requiring real-time, bidirectional communication
• When low latency is critical
• For chat applications, multiplayer games, or collaborative tools

When to use Long Polling:

• As a fallback for older browsers that don’t support SSE or WebSocket
• When you need a simple solution that works across all environments
• For applications with less frequent updates

Conclusion

Choosing the right streaming technology depends on your specific use case, target audience, and technical requirements. SSE is excellent for simple, one-way real-time updates, while WebSocket is ideal for bidirectional, low-latency communication. Long polling serves as a reliable fallback option or for less demanding real-time needs.Consider factors such as browser support, server infrastructure, and the nature of your application when making your decision. In some cases, you might even implement multiple technologies to ensure the best possible experience for all users

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