Many thanks Giuliomoro for your help.
Yes, the monome is a USB serialosc device, is connected directly to the Bela and it shows up when I run ls /dev as ttyUSB0 ... and it even reacts when I run screen /dev/ttyUSB0 connected to the Bela.
Among the several discussions I checked out I was using the script from padenote bela-setup-monome.sh in the discussion you also mentioned https://forum.bela.io/d/240-monome-grid-bela to install libmonome and serialosc in the Bela, and to run serialoscd on the bela boot ... so, I thought it was properly installed and running, but it seems like actually it wasn't.
After reading your reply I decided to install myself libmonome and serialosc following the instructions from here https://monome.org/docs/linux/ ... quite successful since I received this answers from the terminal when I'm running root@bela:~/serialosc/build/bin# ./serialoscd
serialosc [m1000328]: connected, server running on port 17395
serialosc [m1000328]: disconnected, exiting (when I disconnect the monome from the Bela)
If I run serialoscd from a C++program in the Bela IDE I receive the same answer (connecting and disconnecting the monome from the Bela... attached a screenshot of the C++program with the answers of the console)
So ... I asume that the Bela definitely recognise the monome
But (silly enough) I still don't know if I have to run serialoscd in order to make the monome connection active or serialoscd is just a program to monitor if the monome is connected.
And, if I should run serialoscd, I don't know how to do it ... or how to combine the C++ program to run serialoscd and my puredata patch. Sorry but I only know puredata and I have no idea about C++, and not an expert using terminal (https://github.com/BelaPlatform/Bela/wiki/Puredata-and-C-- and examples/08-PureData/customRender/ becomes quite difficult for me to follow)
I also tried to change in my puredata patch the ports to [listen 17395( - [netreceive-u -b] and/or [connect localhost 17395( - [netsend -u -b] ... and didn't work neither
So I keep [listen 12289( - [netreceive -u -b] and [connect localhost 16219( - [netsend -u -b] which are the ports that works at the computer (still not at the Bela)
Thanks again for your help