I was about teaching my friend an intro to node but then
I wonder why this code from nodejs.org:

var http = require('http');

http.createServer(function (req, res) {

    res.writeHead(200, {'Content-Type': 'text/plain'});

    res.end('Hello Worldn');

}).listen(80, '127.0.0.1');

console.log('Server running at http://127.0.0.1:80/');

when hosted, it doesn't accessible from public ip (it's still accessible from localhost though)
while this code from express.js:

var express = require('express');

var routes = require('./routes');

var user = require('./routes/user');

var http = require('http');

var path = require('path');



var app = express();



// all environments

app.set('port', process.env.PORT || 80);

app.set('views', path.join(__dirname, 'views'));

app.set('view engine', 'jade');

app.use(express.favicon());

app.use(express.logger('dev'));

app.use(express.json());

app.use(express.urlencoded());

app.use(express.methodOverride());

app.use(app.router);

app.use(express.static(path.join(__dirname, 'public')));



// development only

if ('development' == app.get('env')) {

  app.use(express.errorHandler());

}



app.get('/', routes.index);

app.get('/users', user.list);



http.createServer(app).listen(app.get('port'), function(){

  console.log('Express server listening on port ' + app.get('port'));

});

does. Please help me modify the basic code the one from nodejs's homepage so that it become accessible from public ip so I can demonstrate it to my friend in a very basic way. The fresh code generated by express.js worked just fine.

What am I missing here?