How can i read data from external devices using different ports in VB?

I am developing a software in VB 2010. I want to modify the software a bit, My current software is a simple "Medical Data Management Software" I want that it should also contain a provision where data's from the medical devices can be read and stored in the software, however, I am afraid because the books i am referring does not cover any section related to hardware interaction.

Please help me solving my problem, is there any other book anyone can recommend me, which can help me learning - how can i read data from external devices using different ports in VB 2010.

Thanks & Regards.