One-Way Real-Time Broadcasting

Server-Sent Events (SSE) allow a server to push updates to the browser in real time. Unlike WebSocket, it's one-directional — the server talks, the browser listens.

const eventSource = new EventSource('/api/notifications');

// Default message handler
eventSource.onmessage = function(event) {
  const notification = JSON.parse(event.data);
  showNotification(notification.message);
};

// Named event types
eventSource.addEventListener('price-update', function(event) {
  updateStockPrice(JSON.parse(event.data));
});

// Error and reconnection handling
eventSource.onerror = function() {
  console.log('Connection lost — browser will auto-reconnect...');
};

// Close when done
function stopListening() {
  eventSource.close();
}

SSE vs WebSocket

Feature	SSE	WebSocket
Direction	Server → Browser only	Bidirectional
Protocol	Regular HTTP	WS / WSS
Auto-reconnect	✅ Built-in	❌ Must implement manually
Browser support	All modern browsers	All modern browsers
Best for	Notifications, feeds, live scores	Chat, games, collaborative tools