help GTB and Modbus

Hello, I am trying to discover your software, which seems to me very interested, for my project of regulation of heating and ventilation.
I wanted to know, if there is a MODBUS library?
What would be handy to create a rise of the different points, on my system of GTB (Technical Management of the Building)

Thank you in advance, sorry for the translation, I use Gooogle translation. thank you.