How to connect online checkout with CRM?

Question

CRM

There is a self-written CRM On hosting and cash desk ATOL 30-F.
How to make checks printed at the checkout from CRM?
Right now we're using the "cashier's seat" from my warehouse, but that's double work.
The cash register is connected to a Windows computer.
I read https://habr.com/ru/post/457684/ , ​​but how to understand "If your CRM is spinning on a hosting, then you will have to leave the port (16732) of the Atolov WEb server to the outside world, which is not very good." How to do this, in which direction to dig and why is it bad to forward ports to the outside world?
In general, the checkout needs to accept commands from CRM. I can send from CRM.

Answer 1

If by hosting you mean VPS / VDS, then you simply raise the VPN there, connect to it from the office and route routes to the checkout host. Everything. And the wolves are full, and the box office "from the big Internet" is not available.

Answer 2

We had cash desks from ShtrihM at the points. Each pickup point has a cash desk connected to a PC on which a KKM web server is installed . It has a number of problems, but in general it works stably. Since the pickup points do not have a white static IP, they are configured in such a way that they would go outside for checks. In our system (CRM) there is a special address for each cash register. From it, the KKM server takes JSON with checks.
Of the problems, only the theme with duplicates arose. We have a wild ten-year legacy and the command to print one check could be duplicated. And KKM the server of the control of a press of duplicates does not conduct. As a result, I wrote down the module for reconciliation of actually punched checks (gone to the tax office) through the PHP-OFD-SDK library .