javascript – How to use redis PUBLISH/SUBSCRIBE with nodejs to notify clients when data values change?-ThrowExceptions

Exception or error:

I’m writing an event-driven publish/subscribe application with NodeJS and Redis. I need an example of how to notify web clients when the data values in Redis change.

How to solve:

OLD only use a reference


uses express,, node_redis and last but not least the sample code from media fire.

Install node.js+npm(as non root)

First you should(if you have not done this yet) install node.js+npm in 30 seconds (the right way because you should NOT run npm as root):

echo 'export PATH=$HOME/local/bin:$PATH' >> ~/.bashrc
. ~/.bashrc
mkdir ~/local
mkdir ~/node-latest-install
cd ~/node-latest-install
curl | tar xz --strip-components=1
./configure --prefix=~/local
make install # ok, fine, this step probably takes more than 30 seconds...
curl | sh

Install dependencies

After you installed node+npm you should install dependencies by issuing:

npm install express
npm install
npm install hiredis redis # hiredis to use c binding for redis => FAST :)

Download sample

You can download complete sample from mediafire.

Unzip package

unzip # can also do via graphical interface if you prefer.

What’s inside zip


const PORT = 3000;
const HOST = 'localhost';

var express = require('express');

var app = module.exports = express.createServer();

app.use(express.staticProvider(__dirname + '/public'));

const redis = require('redis');
const client = redis.createClient();

const io = require('');

if (!module.parent) {
    app.listen(PORT, HOST);
    console.log("Express server listening on port %d", app.address().port)

    const socket  = io.listen(app);

    socket.on('connection', function(client) {
        const subscribe = redis.createClient();
        subscribe.subscribe('pubsub'); //    listen to messages from channel pubsub

        subscribe.on("message", function(channel, message) {

        client.on('message', function(msg) {

        client.on('disconnect', function() {


    <script src="/"></script>
    <script src="/javascripts/jquery-1.4.3.min.js"></script>
    <div id="content"></div>
        $(document).ready(function() {
            var socket = new io.Socket('localhost', {port: 3000, rememberTransport: false/*, transports: ['xhr-polling']*/});
            var content = $('#content');

            socket.on('connect', function() {

            socket.on('message', function(message){
                content.prepend(message + '<br />');
            }) ;

            socket.on('disconnect', function() {


Start server

cd pbsb    
node app.js

Start browser

Best if you start google chrome(because of websockets support, but not necessary). Visit http://localhost:3000 to see sample(in the beginning you don’t see anything but PubSub as title).

But on publish to channel pubsub you should see a message. Below we publish "Hello world!" to the browser.

From ./redis-cli

publish pubsub "Hello world!"


here’s a simplified example without as many dependencies.
You do still need to npm install hiredis redis

The node JavaScript:

var redis = require("redis"),
    client = redis.createClient();

client.on("message", function(channel, message){
  console.log(channel + ": " + message);

…put that in a pubsub.js file and run node pubsub.js

in redis-cli:

redis> publish pubsub "Hello Wonky!"
(integer) 1

which should display: pubsub: Hello Wonky! in the terminal running node!

Additional 4/23/2013: I also want to make note that when a client subscribes to a pub/sub channel it goes into subscriber mode and is limited to subscriber commands. You’ll just need to create additional instances of redis clients. client1 = redis.createClient(), client2 = redis.createClient() so one can be in subscriber mode and the other can issue regular DB commands.


Complete Redis Pub/Sub Example (Real-time Chat using Hapi.js &

We were trying to understand Redis Publish/Subscribe (“Pub/Sub“) and all the existing examples were either outdated, too simple or had no tests.
So we wrote a Complete Real-time Chat using Hapi.js + + Redis Pub/Sub Example with End-to-End Tests!

The Pub/Sub component is only a few lines of node.js code:

Rather than pasting it here (without any context) we encourage you to checkout/try the example.

We built it using Hapi.js but the chat.js file is de-coupled from Hapi and can easily be used with a basic node.js http server or express (etc.)


Handle redis errors to stop nodejs from exiting. You can do this by writing;

subcribe.on("error", function(){
  //Deal with error

I think you get the exception because you are using the same client which is subscribed to publish messages. Create a separate client for publishing messages and that could solve your problem.


Check out acani-node on GitHub, especially the file acani-node-server.js. If these links are broken, look for acani-chat-server among acani’s GitHub public repositories.


If you want to get this working with 0.7 AND an external webserver you need to change (besides the staticProvider -> static issue):

a) provide the domain name instead of localhost (i.e. var socket = io.connect(‘’); ) in the index.html

b) change HOST in app.js (i.e. const HOST = ‘’; )

c) and add sockets in line 37 of app.js (i.e. ‘socket.sockets.on(‘connection’, function(client) { …’ )


Update to the code:


now renamed to


see migration guide


according to @alex solution. if you have an error like this one as per @tyler mention:

        throw e; // process.nextTick error, or 'error'

event on first tick ^ Error: Redis connection to failed - ECONNREFUSED, Connection refused at Socket.

then you need to install Redis first. check this out:

Leave a Reply

Your email address will not be published. Required fields are marked *