I am new in this technology. But I want to learn this problem for my personal skills. Everything should be open source API.
1. How do client systems get calls on their systems? (What Hardware need to be configure)
2. After Getting call on their system, I need to get that number and hit to my API to get information from my database system, if exists. Else I can able to fill the user details and do entry in the DB.
What are the hardware required for setup above feature and what are the open source software needed to fulfill my requirements?