In order to find which devices are available on a box, you can run:

```bash
	$ dmesg | grep tty
	serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
	00:0c: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
```
From this output, we can guess that there is 1 serial interface (/dev/ttyS0). You might possibly have more than one interface on your machine, this tutorial considers that you are using device 1 (ttyS0), if you use the second device, you will need to change ttyS0 by ttyS1.