I would like to introduce my software -
Arduino Control Center. I hope it is not an issue since the program is not freeware, but I think it perfectly fit into this topic.
What i had in mind when I was started this project is to develop a software which can control group of Arduino devices(UNO,NANO,MEGA) from one place with data acquisition, e-mail and SMS notifications, visual and sound alerts, charts, web interface(http and https) with integrated web server. Basically, all you need for full control of many Arduino devices, all packed in single folder, portable and, at least I think, easy to setup.
Here is a software
Functional diagram:
How it works,
supported hardware, free downloads for Windows, Linux(Ubuntu) and other useful information you can find on my web page
https://lanmisoft.com/, but I'll be glad to answer your questions here if you find that software can be useful for your IoT projects.