Socket.io in express js : Router.use requires middleware function but got undefined

Question

I am trying to integrator socket.io in my express js application (Created by express generator).

But it didn't worked.

Added following in bin/www

app.io = require('socket.io')();
app.io.attach(server);

When i modify app.use('/', index); with app.use('/', require('./routes/index')(app.io)); in app.js file i got the following error

*

Router.use requires middleware function but got undefined

*

user2263572 · Accepted Answer · 2017-04-18T15:41:12.367

3

Here is how you can implement socket.io with express.

var express = require('express')
var app = express();
var http = require('http').Server(app);
var io = require('socket.io')(http);

//serve static files and index.html
app.use(express.static(__dirname + '/'));
app.get('/', function(req, res){ res.sendFile(__dirname + '/index.html'); });

io.on('connection', function(socket){
    //logic handled in here
});

http.listen(7000,function(){ console.log('listening on port: 7000'); });

The above code has one route for handling the serving of index.html, but of course you can extend with additional routes the same way you would in any other app.

Here is how you can have access to socket.io within a route in express generator.

In www:

var server = http.createServer(app);
var io = require('socket.io')(server);
module.exports = {io:io}

Within index.js

router.get('/', function(req, res, next) {
  var io = require('../bin/www')
  console.log('I now have access to io', io)
  res.render('index', { title: 'Express' });
});

Note, the above example is purely showing you how to gain access to the io object within index.js. There are many better ways to require socket.io and pass the io object around, but those decisions seem to be outside the scope of this question.

edited Apr 18 '17 at 15:41

answered Apr 18 '17 at 15:14

user2263572

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Where can i add this ?? – Blessan Kurien Apr 18 '17 at 15:15
I want to use io object in `routes/index.js` but as per yr code everything is do in `app.js` file – Blessan Kurien Apr 18 '17 at 15:18
You can make these changes within project_root/bin/www. – user2263572 Apr 18 '17 at 15:22
But how do i use `io` in `index.js` ? – Blessan Kurien Apr 18 '17 at 15:23
https://www.sitepoint.com/understanding-module-exports-exports-node-js/ – user2263572 Apr 18 '17 at 15:26
Just added yr code to `www` no errors show but `io.on` not fired – Blessan Kurien Apr 18 '17 at 15:31
If you do "module.exports = io" in www, you can do io = require('path_to_module_exports_file') in another file and have access to the io object. – user2263572 Apr 18 '17 at 15:32
whats this `path_to_module_exports_file` means?? s – Blessan Kurien Apr 18 '17 at 15:35
I updated the answer to reflect your exact situation. – user2263572 Apr 18 '17 at 15:41
Got it but there is another error `io.on('connection',function(obj){ console.log('Client connected'); });` throws io.on is not a function – Blessan Kurien Apr 18 '17 at 15:49
In module.exports I assigned the io object to an io key. Just habit since many times you will want to export multiple variables. Try io.io.on('connection'.....rest of your code, and it should work. – user2263572 Apr 18 '17 at 15:53
No errors one more question for firing `io.connection` is it necessary socket client library?? – Blessan Kurien Apr 18 '17 at 15:55
Yes, you need to include the socket.io javascript within your front-end as well else you will not be able to make a connection. – user2263572 Apr 18 '17 at 15:56
Thanks let me try it – Blessan Kurien Apr 18 '17 at 15:57

Socket.io in express js : Router.use requires middleware function but got undefined

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