app-server.js

var express = require('express');
var _ = require('underscore');
var app = express();

var connections = [];
var title = 'Untitled Presentation';
var audience = [];
var speaker = {}; //only 1 speaker so just user an object

app.use(express.static('./public'));
app.use(express.static('./node_modules/bootstrap/dist'));

var server = app.listen(3000);
var io = require('socket.io').listen(server);

io.sockets.on('connection', function(socket){

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

        var member = _.findWhere(audience, { id: this.id });

        if (member) {
            audience.splice(audience.indexOf(member), 1);
            io.sockets.emit('audience', audience);
            console.log("Left: %s (%s audience members)", member.name, audience.length);
        }

        connections.splice(connections.indexOf(socket), 1);    //gives us the index of the array of the current socket & how many sockets to remove
        socket.disconnect();
        console.log("Disconnected: %s sockets remaining.", connections.length);
    });

    socket.on('join', function(payload){
        var newMember = {
            id: this.id,
            name: payload.name,
            type: 'member'
        };
        this.emit('joined', newMember);
        audience.push(newMember);
        io.sockets.emit('audience', audience);
        console.log("Audience Joined: %s", payload.name);
    });

    socket.on('start', function(payload) {
        speaker.name = payload.name; //send speaker name with that payload
        speaker.id = this.id;
        speaker.type = 'speaker';
        this.emit('joined', speaker);
        io.sockets.emit('start', {title: title, speaker: speaker.name});
        console.log("Presentation Started: '%s' by %s", title, speaker.name);
    });

    socket.emit('welcome',{
        title: title,
        audience: audience,
        speaker: speaker.name
    });

    connections.push(socket);
    console.log("Connected: %s sockets connected", connections.length);
});


console.log('Polling server is running at "http://localhost:3000"');