I see a big discrepancy in your answers between
That serial part was just for testing.
and
But the one that I'm developing the most is the one that i posted in the first 3 comments.
The version you posted is definitely not working because it has a complete mess on the serial interface. If you're developing with that version you'll not succeed until you removed all debugging output. You'll have to find another way for debugging, the serial interface is used for the ModBus.
My SCADA supports ModBus RTU, ASCII and TCP/IP,
And which one did you configure for the tests?