Reverse signal

Hi! Receipt of data by the Arduino RX and I would reverse the signal send by bluetooth software but I have no idea. I searched for information but always end up coming to how to do hardware. Any idea? Thank you.

What do you mean by reversing the signal?
Do you want the logical 0 and 1 to change in to the opposite?
Do you want to reproduce the signal backwards?
Something else?

I use the library "Brain" I returns a string with several numbers separated by commas. To capture the data correctly I have to use an inverter and my intention is not to have to use the inverter.

So you want software solution instead of a digital inverter? I know software serial can invert inputs. It wont do high baud rate though.