How to set up WebSockets, Server-Sent Events, and Long Polling for Real-Time Features in SaaS Products

Real-time functionality is a vital aspect of Software as a Service (SaaS) products, offering users immediate responses and seamless interactions. By enabling real-time collaboration, data synchronization, and instant updates, SaaS applications enhance user experiences and boost productivity. Whether facilitating live communication, automating processes, or supporting IoT and AI integration, real-time features ensure that SaaS products stay competitive in a rapidly evolving digital landscape.

In an increasingly connected digital world, real-time features have become a critical aspect of SaaS (Software as a Service) products. Techniques such as:

  1. WebSockets (server push), 
  2. Server-Sent Events (server push)
  3.  Long Polling (client pull)

are widely used to achieve real-time functionality.

Each of these approaches has its strengths and weaknesses. This blog post will compare these technologies and help you decide which one is the most suitable for your needs.

(Client pull refers to the process where the client requests updates from the server at regular intervals. On the other hand, server push is when the server actively sends updates to the client without the client explicitly requesting them. It is the reverse of client pull.)

1. WebSockets:

WebSockets provide a full-duplex communication channel between the client and the server over a single, long-lived connection. This means both the client and the server can initiate communication, allowing for real-time data exchange.


– Full-duplex communication: Both the client and server can send data simultaneously.

– Persistent connections: Once established, the connection remains open, reducing the overhead associated with HTTP connections.


– Requires more resources: Keeping a connection open can consume more server resources.

– Not fully supported by all proxies and firewalls: Some older infrastructure may not support WebSockets.

How to establish WebSocket connection:

To establish a WebSocket connection in JavaScript:

// Client side
const socket = new WebSocket('ws://your-server-url');
socket.onopen = () => {
console.log('WebSocket connection established.');
socket.onmessage = (event) => {
const message =;
console.log('Received message:', message);
socket.onclose = () => {
console.log('WebSocket connection closed.');
// Sending a message to the server
socket.send('Hello, server!');

On the server side, you would handle WebSocket connections using the appropriate libraries for your programming language. Here’s a simple example using Node.js and the ws library:

// Server Side
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection', (socket) => {
console.log('WebSocket connection established.');
socket.on('message', (message) => {
console.log('Received message:', message);
// Handle the message from the client
// Sending a message to the client
socket.send('Hello, client!');
socket.on('close', () => {
console.log('WebSocket connection closed.');

2. Server-Sent Events (SSE):

SSE is a standard that allows a server to push real-time updates to the client over HTTP. Unlike WebSockets, SSE is a one-way communication channel; the server can send messages to the client, but not the other way around.

The HTML5 standard by W3C includes a standard JavaScript client API called EventSource, which is supported by most modern browsers. For browsers that don’t have native support for the EventSource API, there are polyfills available as alternatives.


– Efficient for one-way data streams: If your application primarily requires server-to-client updates, SSE can be a more straightforward option than WebSockets.

– Built on HTTP: SSE works well with existing HTTP infrastructure such as load balancers and proxies.


– One-way communication: Clients cannot send data to the server using SSE.

– Not as widely supported as WebSockets: Some browsers, notably Internet Explorer, do not support SSE.

How to establish SSE connection:

On the client side, you can set up an SSE connection using JavaScript:

//Client Side
const eventSource = new EventSource('/sse-endpoint');
eventSource.onopen = () => {
console.log('SSE connection established.');
eventSource.onmessage = (event) => {
const message =;
console.log('Received message:', message);
eventSource.onerror = () => {
console.log('SSE connection error occurred.');
// SSE connection closed automatically if needed.

On the server side, you need to set up an SSE endpoint to send updates:

//Server Side
const express = require('express');
// const app = express();
app.get('/sse-endpoint', (req, res) => {
res.setHeader('Content-Type', 'text/event-stream');
res.setHeader('Cache-Control', 'no-cache');
res.setHeader('Connection', 'keep-alive');
res.write(': Comment to keep the connection open\n\n');
// Periodically send updates to the client
const interval = setInterval(() => {
const message = 'New update!';
res.write(`data: ${message}\n\n`);
}, 1000);
// Clean up the SSE connection if needed
req.on('close', () => {
// Perform any necessary cleanup
app.listen(3000, () => {
console.log('Server listening on port 3000');

3. Long Polling:

Long Polling is a variation of the traditional polling technique. The client sends a request to the server, and the server holds the request open until it has data to send back to the client. Once the client receives the data, it immediately sends another request, and the process repeats.


– Broad compatibility: Long polling works with almost all browsers and network infrastructure.

– Simplicity: It’s easy to implement since it operates over standard HTTP.


– Latency: There can be a delay between when an event occurs and when the client receives the update.

– More server overhead: Long polling can require more resources than WebSockets or SSE as it opens and closes connections more frequently.

How to establish Long Polling connection:

On the client side, you can implement long polling using JavaScript:

// Client Side
function pollServer() {
.then((response) => response.text())
.then((message) => {
console.log('Received message:', message);
// Handle the message from the server
// Initiate the next long polling request
.catch((error) => {
console.log('Long polling request failed:', error);
// Retry after a delay in case of errors
setTimeout(pollServer, 3000);
// Start the initial long polling request

On the server side, you would handle the long polling request:

//Server Side
const express = require('express');
const app = express();
app.get('/long-polling-endpoint', (req, res) => {
// Simulating an asynchronous operation
setTimeout(() => {
const message = 'New update!';
}, 2000);
app.listen(3000, () => {
console.log('Server listening on port 3000');


In conclusion, when it comes to real-time features in SaaS products, WebSockets have emerged as the most popular and widely used technology. They provide a full-duplex, persistent connection between the client and server, making them suitable for applications requiring bidirectional real-time data exchange. WebSockets are commonly employed in chat systems, collaboration tools, multiplayer games, and financial trading platforms.

Server-Sent Events (SSE) offer an alternative approach for real-time features, particularly for one-way communication scenarios where the server needs to push updates to the client. SSE has moderate adoption and finds applications in systems that require real-time notifications, live streaming, and event-driven updates. However, SSE may face limitations in terms of browser support and compatibility, especially with older browsers.

Long Polling, while not as popular as WebSockets, remains relevant for certain use cases. It is a technique that can work with almost all browsers and network infrastructure, providing a simple alternative for achieving real-time functionality when WebSockets or SSE are not available or suitable. Long Polling is commonly used in applications that require real-time updates but may lack the necessary infrastructure or browser support for WebSockets or SSE.

Ultimately, the choice among WebSockets, SSE, and Long Polling depends on the specific requirements of the SaaS product and the infrastructure constraints. It may also be worth considering a combination of these techniques to cater to different use cases within the application. Keeping up with the latest trends and considering factors such as performance, scalability, and compatibility will help in making informed decisions about the most suitable real-time technology for a SaaS product.

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