We have a 'stock link' that was previously developed by a company called Zero 1, it links our instore epos system to our magento1 site.
It takes a stock number for any given sku from a website maintained by our instore epos software and updates magento with stock numbers only, and ithen it sends orders back from Magento to our instore epos to keep the stock numbers up to date.
I will attach a zip with what i think is the majority of the files from our current magento 1 installation so you can see what I am taking about.
This needs to work on our new Magento2 site
Current Magento 2 version 2.2.9
Timeframe 2-4 weeks
Hi I checked your requirement related to extension which is work in Magento 1 but not working in Magento 2 and if you allow me then I can do modification so it will work in your current version 2.2.9.
Morning These kind of integration always need a good definitions of the events, becasue you already have a old module you have a good definition of all the proccess. Regards