[node.js] How to get Node.JS Express to listen only on localhost?

I have an application that I have behind a reverse proxy, I would like for it to only listen to localhost/127.0.0.1.

I expected this to work:

app.listen(3001, 'localhost');

or

app.listen(3001, '127.0.0.1');

...but instead I get an error:

node.js:201
    throw e; // process.nextTick error, or 'error' event on first tick
          ^
TypeError: Cannot read property 'port' of null
    at Object.<anonymous> (/home/ctoledo/hive-go/go.js:204:76)
    at Module._compile (module.js:441:26)
    at Object..js (module.js:459:10)
    at Module.load (module.js:348:31)
    at Function._load (module.js:308:12)
    at Array.0 (module.js:479:10)
    at EventEmitter._tickCallback (node.js:192:40)

Running the application without a specifying the hostname works fine, ie., app.listen(3001);.

I am running Node v0.6.14 and express@2.5.5 and have read this google groups discussion and have found this comment in Express application.js saying: "This method takes the same arguments as node's http.Server#listen()."

Thanks for any help.

You are having this problem because you are attempting to console log app.address() before the connection has been made. You just have to be sure to console log after the connection is made, i.e. in a callback or after an event signaling that the connection has been made.

Fortunately, the 'listening' event is emitted by the server after the connection is made so just do this:

var express = require('express');
var http = require('http');

var app = express();
var server = http.createServer(app);

app.get('/', function(req, res) {
    res.send("Hello World!");
});

server.listen(3000, 'localhost');
server.on('listening', function() {
    console.log('Express server started on port %s at %s', server.address().port, server.address().address);
});

This works just fine in nodejs v0.6+ and Express v3.0+.