Socket.IO -- ReferenceError: io is not defined, used to work on another website

I have always used the code below to do this, in another website it worked fine, but now it's not.

server.js

var io = require('socket.io').listen(8080);

var users = {};
console.log("Sever is now running");

io.sockets.on('connection', function (socket) { 
    console.log("connection");
    socket.emit('connected');

});

The server seems to be fine, I think. It shows the console.log message anyways. Though the second console.log doesn't show up, but I just figured it was because of the error or whatever.

data.js

var socket = io.connect(window.location.origin, {port:8080});

$(document).ready(function(){
    socket.on('connected', function () {    
        alert("A");
    });
});