How to write a cross-platform desktop application (Windows, Linux) in 2016?

Question

linux

Actually a subject. The details are that the program will work with trading equipment. Type of fiscal apparatus and barcode scanner and be sure to support both windows and linux.
I don’t know much about the topic because I didn’t develop it for the desktop. Prompt plz.

Answer 1

Qt
Out of the box is
https://doc.qt.io/qt-5/qtserialport-index.html

Answer 2

It is possible on nwjs.io , then your application can also be launched in any browser.

Answer 3

php ;)

Answer 4

Python3