If you are running your example in Linux you need to load the ACMtty module so you system makes a Serial USB device available for your user space.
As root and only if you have cdc-acm module compiled for your current kernel:
modprobe cdc-acm
Once this module is loaded and your device connected you should find a device named following this pattern: /dev/ttyACM*
You may have already installed the right user space tools and libraries but you also need to install the device.