port-checker.js

var net = require('net'),
	timeout = 500;

module.exports.checkOpen = function(port, cb) {
	var open = false,
		checked = false,
		tid, conn;
	var onClose = function() {
		if( checked ) return;
		checked = true;
		clearTimeout(tid);
		delete conn;
		cb(open);
	};
	var onOpen = function() {
		open = true;
		conn.end();
	};
	tid = setTimeout(function() {
		conn.destroy();
	}, timeout);
	conn = net.createConnection(port, 'localhost', onOpen);
	conn.on('close', function() { if( !checked ) { onClose() }});
	conn.on('error', function() { conn.end(); });
	conn.on('connect', onOpen);
};