function onError(error) {
	if (error.syscall !== 'listen') {
		throw error;
	}
	
	var bind = typeof port === 'string' ? 'Pipe ' + port : 'Port ' + port;
	
	// handle specific listen errors with friendly messages
	switch (error.code) {
		case 'EACCES':
			console.error(bind + ' requires elevated privileges');
			process.exit(1);
			break;
		case 'EADDRINUSE':
			console.error(bind + ' is already in use');
			process.exit(1);
			break;
		default:
			throw error;
	}
}
Event listener for HTTP server "error" event