SockJS is a JavaScript library that provides a WebSocket-like object in environments where true WebSockets are not available or not fully supported. It is designed to work both on the client-side and server-side to enable seamless communication between the two. SockJS provides a consistent API and attempts to provide a low-latency, full duplex, cross-domain communication channel that can work even behind restrictive corporate proxies.

What are sockjs's main functionalities?

Server-side WebSocket emulation

This code sample demonstrates how to create a SockJS server that emulates a WebSocket. It listens for connections on the '/echo' path and simply echoes back any messages it receives.

const http = require('http');
const sockjs = require('sockjs');
const echo = sockjs.createServer({ prefix: '/echo' });
echo.on('connection', function(conn) {
  conn.on('data', function(message) {
    conn.write(message);
  });
});
const server = http.createServer();
echo.installHandlers(server, { prefix: '/echo' });
server.listen(9999, '0.0.0.0');

Client-side WebSocket emulation

This code sample shows how to create a SockJS client that connects to a SockJS server. It sends a message when the connection is opened and logs any messages it receives before closing the connection.

const SockJS = require('sockjs-client');
let sock = new SockJS('http://localhost:9999/echo');
sock.onopen = function() {
  console.log('open');
  sock.send('test');
};
sock.onmessage = function(e) {
  console.log('message', e.data);
  sock.close();
};
sock.onclose = function() {
  console.log('close');
};

Other packages similar to sockjs

Readme

Source

SockJS-node server

To install sockjs-node run:

npm install sockjs

A fully working echo server would look like:

var http = require('http');
var sockjs = require('sockjs');

var sockjs_opts = {sockjs_url: "http://127.0.0.1:8000/lib/sockjs.js"};

var sjs_echo = new sockjs.Server(sockjs_opts);
sjs_echo.on('open', function(conn) {
    conn.on('message', function(e) {
        conn.send(e.data);
    });
});

var normal_handler = function(req, res) {
        res.writeHead(404);
        res.end("Not found.");
};

var server = http.createServer();
server.addListener('request', normal_handler);
server.addListener('upgrade', normal_handler);

sjs_echo.installHandlers(server, {prefix:'[/]echo'});

server.listen(9999, '0.0.0.0');

FAQs

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Last updated on 11 Aug 2011

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