A simple node.js/express example on how to 'misuse' cluster to actually create several process forks, and set their own port for each.

fork-with-ports.js

var express = require('express'),
	cluster = require('cluster'),
	http = require('http'),
	numCPUs = require('os').cpus().length,
	basePort = 1100;

var app = express();
app.use(express.cookieParser());
app.use(express.logger('short'));
app.use(express.session({
	secret: 'keyboard cat',
	key: 'backendSession',
	// Disabled for better readability
	//cookie: { secure: true },
	store: new express.session.MemoryStore
}));

app.get('/api/*', function(req, res) {
	var session = req.session,
	body = 'Hello World from ' + app.locals.port;
	
	// Store something to the session
	// Note: In a real-world example, don't set a cookie when you dont't want
	// to disable Nginx caching mechanisms.
	session.stickyPort = app.locals.port;
	
	res.setHeader('Content-Type', 'text/plain');
	res.setHeader('Content-Length', body.length);
	res.end(body);
});

if (cluster.isMaster) {
	// Fork workers.
	for (var i = 0; i < numCPUs; i++) {
		// Since we don't share the same port, pass it as an env. variable
		cluster.fork({ 'SLAVE_PORT': basePort + i});
	}

	cluster.on('exit', function(worker, code, signal) {
		console.log('worker ' + worker.process.pid + ' died');
	});
} else {
	// Fetch the port fron ENV
	var port = process.env['SLAVE_PORT'];
	
	// Workers can share any TCP connection
	// In this case its a HTTP server
	
	app.listen(port);
	app.locals.port = port;
	console.log('Slave listening at port', port);
}