Node.js サーバーを 80 番ポートで動かす ref: http://qiita.com/janus_wel/items/ee0ea612a075f197a219

default.json

{
    "user": "vagrant",
    "port": 80
}

hello.js

var http = require('http');
var PORT = 80;
var HOSTNAME = '127.0.0.1';
var USER = 'nodejs';

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(PORT, HOSTNAME, function () {
    console.log('change user');
    process.setuid(USER);
});

console.log('Server running at http://' + HOSTNAME + ':' + PORT + '/');

well-known-port.js

var WELL_KNOWN_PORT = 1024;

var config = require('config');
var port = config.port || 80;
var user = config.user || 'nodejs';

var os = require('os');
var hostname = os.hostname() || '127.0.0.1';

var http = require('http');

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(port, hostname, function () {
    if (port < WELL_KNOWN_PORT) {
        console.log('Attempting setuid to user "' + user + '"...');
        try {
            process.setuid(user);
            console.log('Succeeded to setuid');
        } catch (err) {
            console.log('Failed to setuid');
            process.exit(1);
        }
    }
});

console.log('Server running at http://' + hostname + ':' + port + '/');