Sharing socket.io to other modules gives empty object

Question

I am trying to share `socket.io`'s socket object in different node.js modules although I fail and get empty object with ``` Cannot call method 'on' of undefined ``` My code : app.js ``` var express = require('express') , app = express(); var server = require('http').createServer(app) , io = require('socket.io').listen(server) var routes = require('./routes') , path = require('path') , rss = require('./routes/rss') // ... exports.io = io; ``` routes/rss.js ``` io = require(__dirname + '/../app'); console.log(io); io.sockets.on('connection', function( console.log("Connection on socket.io on socket"); // .. do stuff }); ``` That's the output I get from this : ``` $ node app.js info - socket.io started {} /home/XXX/programming/nodejs/node-express-aws/routes/rss.js:10 io.sockets.on('connection', function(socket){ ^ TypeError: Cannot call method 'on' of undefined at Object.<anonymous> (/home/XXX/programming/nodejs/node-express-aws/routes/rss.js:10:12) at Module._compile (module.js:456:26) a…

Accepted Answer

Since, in `app.js`, you have:

```
exports.io = io;
```

then you would need to use it like so:

```
var app = require('../app');
var io = app.io;
```

That is you say, you attached a property called `io` to the module, so when you require that module, you get an object that has the `io` property set.

You could also do

```
module.exports = io;
```

and then leave `rss.js` as you have it now.

All that said, if you're running `app.js` with Node, you'll much more commonly see the `io` object injected into other modules (instead of the other way around); for example:

`app.js`

```
var express = require('express')
  , app = express();

var server = require('http').createServer(app)
  , io = require('socket.io').listen(server)

var routes = require('./routes')
  , path = require('path')
  , rss = require('./routes/rss')

// ...

rss(io); // pass `io` into the `routes` module,
         // which we define later to be a function
         // that accepts a Socket.IO object
```

`routes/rss.js`

```
module.exports = function(io) {
  io.sockets.on('connection', function(
    console.log("Connection on socket.io on socket");
    // .. do stuff 
  });
}
```

Sharing socket.io to other modules gives empty object

Solution

Problem