Realtime & WebSockets

Server-Sent Events (SSE) Stream

Lightweight, HTTP-based unidirectional streaming. Subscribe to live server notifications, background task updates, and automated heartbeats using the native browser EventSource API over standard HTTP/1.1 or HTTP/2 without custom socket libraries.

/api/v1/stream/notifications?samples=truedisconnected

Auto-emit mock notifications (every 8s):

Keepalive: : ping every 15s

[12:00:00][system]:SSE terminal initialized. Click "Connect SSE Stream" to establish an HTTP persistent event stream.

SSE Protocol Headers Reference

The stream endpoint sends the following HTTP response headers to keep connections persistently open:

Header	Value	Purpose
Content-Type	text/event-stream	Identifies payload as EventSource stream format.
Cache-Control	no-cache, no-transform	Prevents intermediate proxies and CDNs from buffering chunks.
Connection	keep-alive	Maintains persistent long-lived TCP connection.
X-Accel-Buffering	no	Instructs Nginx reverse proxies to stream chunks immediately.

Client Integration Code

Production examples for native browser EventSource, React hooks, and cURL:

// Client Integration using Native Browser EventSource

const streamUrl = '/api/v1/stream/notifications?samples=true';

const eventSource = new EventSource(streamUrl, { withCredentials: true });

// 1. Connection opened

eventSource.onopen = () => {

console.log('SSE connection established');

};

// 2. Listen for custom typed events

eventSource.addEventListener('notification', (event) => {

const payload = JSON.parse(event.data);

console.log('New notification received:', payload);

});

// 3. Listen for general messages

eventSource.onmessage = (event) => {

console.log('Message event:', event.data);

};

// 4. Handle errors & auto-reconnect

eventSource.onerror = (err) => {

console.error('SSE Error:', err);

};

Server-Sent Events vs WebSockets

When to choose Server-Sent Events over WebSockets for application architecture:

Capability	Server-Sent Events (SSE)	WebSockets (WS)
Communication Direction	Unidirectional (Server → Client)	Full-duplex bidirectional
Transport Layer	Standard HTTP/1.1 or HTTP/2	TCP upgrade to WebSocket protocol
Automatic Reconnection	Native browser auto-retry	Custom application retry required
Firewall / Proxy Traversal	Seamless (Standard HTTP GET)	Requires WebSocket proxy support

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