How do I implement real-time updates using Server-Sent Events (SSE)

Set up a server that supports SSE

In order to implement real-time updates using Server-Sent Events (SSE), you must first set up a server that supports this technology. Depending on the language and framework you are using, there are different ways of doing this. For example, if you're working with Node.js, you can use the sse package. This package provides an easy way to create an SSE endpoint in your application.

const sse = require('sse');
const http = require('http');
 
// Create an HTTP server 
const server = http.createServer();  
server.listen(8080);   // Listen on port 8080 

 // Create an EventSource endpoint  
 const eventSource = new sse(server);    

Create an endpoint on your server

In order to implement real-time updates using Server-Sent Events (SSE), you need to create an endpoint on your server. This is a URL that will be used by the client side code to connect and receive updates from the server. The endpoint should support SSE, which means it must return data in text/event-stream format. To do this, you can use any web framework of your choice such as NodeJS or PHP.

For example, if you are using NodeJS, then you can set up a simple HTTP server with Express like this:

const express = require('express');
const app = express();
app.get('/sse', (req, res) => {   // Create an endpoint for SSE   res.writeHead(200, {     'Content-Type': 'text/event-stream',     'Cache-Control': 'no-cache'   });    // Send events here... });

Once the endpoint is created and running on your server, it's time to move onto the next step - creating an EventSource object on the client side.

In order to receive real-time updates from your server using Server-Sent Events (SSE), you need to create an EventSource object on the client side. This can be done by calling the constructor of EventSource, passing in a URL that points to your endpoint. For example:

const eventSource = new EventSource('https://example.com/sse');

The above code will create a new instance of EventSource. You can then add listeners for various events such as open, message and error.

eventSource.addEventListener('open', () => {
  console.log('Connection opened!');
});
eventSource.addEventListener('message', (e) => {
  console.log(`Message received: ${e}`);
});
eventSource.addEventListener('error', (err) => {
  if (err === 'Error') { // Connection closed!   } else { // Some other error occurred   } }); 

Once you have added all necessary listeners, you are ready to start receiving real-time updates from your server.

To send updates from the server, you need to use a Server-Sent Events (SSE). This is a technology that allows for real-time communication between the client and the server. To implement SSE, first set up a server that supports it, then create an endpoint on your server where clients can connect and receive updates. On the client side, create an EventSource object which will be used to listen for events sent by the server.

// Create an EventSource object 
let eventSource = new EventSource('http://example.com'); 
  
// Listen for messages sent by the server 
eventSource.onmessage = function(e) { 

    // Handle message received from the Server  
    console.log(e);    					      }

Once this setup is complete, when you want to send an update from your server simply call eventSource.send(), passing in any data or information that needs to be sent as part of the update.

Useful Links

• MDN Web Docs - Server-Sent Events
• HTML5 Rocks - Introduction to Server Sent Events (SSE)
• LogRocket Blog - How to Implement Realtime Updates Using Server Sent Events (SSE)
• Medium Article - Understanding and Implementing Server Sent Event in NodeJS & JavaScript