I wonder if your assumptions are correct. They are probably just using gethostbyname() / getaddrinfo() to find the IP and then it's the OS (Windows) that is responsible for the behavior you're seeing.
As I'm sure you know those function are part of socket programming functions of the OS. Based on BSD originally but Microsoft must have added code to deal with netbios, wins and whatever they've been doing since the days of Wfw.
Linux by comparison only deals with name resolution by DNS and manual hosts files. I can't think of anything else right now at least.
I think we are at cross purposes. I'm not saying that the app can print from INSIDE the browser. I'm saying that the app can present the HTML TO the browser and the browser's print function can print directly without needing a third party application. Straight from browser to printer.
Thanks Scott. We are at cross purposes because I was being very specific when I mentioned where the print is rendered. In a lot of label applications you can't have it rendered in the web browser from html because you need to send special commands to the label printer inside the label. More advanced label printer have lots of special commands, for instance to generate bar codes on the fly (not from graphics) or time of day or a serial number for each label printed.
Dymo doesn't have that. You can print these exact labels directly, nothing special needed. And this software doesn't need that, they have three products that print identically from the same vendor, they all print the same codes and only this one do they not provide a direct print option. But even in the cases that you are giving, that's not printing exactly, it's using a third party application to do some of your work for you. Again, totally nothing wrong with that, but it's a hokie setup and a really bad design to keep basic printing out of your platform agnostic app and require a potentially buggy or discontinued third party and very limited application to do that simple task for you.
Same vendor, but different product, uses MS Word in the same way. Can't be bothered to do basic tasks in their software and actually put in more effort, rather than less, to make Word do it for them.
This is working on several machines now. But @romo reports that it is still hit or miss, it's not a reliable or permanent fix, but it more reliable than other attempts. It remains, as MS has stated, somewhat random.