How to get the Caller Info from VoIP in real-time in a .NET Application?

Question

I am working on a project which includes a lot of VoIP functions. I don't have access to the source code of the previous system that was being used so I can't dissect it to find out what I need to know. I will describe how the previous system used to work and then ask my question.

First, the old system that we have been using depends on Physical Phones which receive calls over the internet. There is a Desktop App installed on our computer which somehow takes the phone call received by the phone and shows that phone number on the Desktop App. Which uses that number to look up data about the caller. But the problem is that this Desktop App is over a decade old and has not been updated since. So we want to build a new Web Based Application with .NET that will do the same. My question is:

1- How do I fetch the Caller Information From the Physical Phone and use it how I want? The phone being used is SNOM 760 but its possible that other brands or models be used in the future.

2- Let's say that a specific page is always opened on the browser. How do I transfer the caller number to the server and then show a pop up with the information about the caller in that page that's always opened in the browser in a RELIABLE way? What about when that specific page is not opened? Remember that the phone that is receiving this call is not directly in communication with the server. But that is also not a restriction. I read somewhere while researching that I could have my server take the call first and then transfer it to that physical phone. The only restriction is that we use VoIP phones/numbers.

Like I said, I have very vague information on the subject. Any help is appreciated. I've studied that I could use Twillio or other such third party services to achieve this task but I just wanted to know if I can do it myself instead of relying on someone else and hoping they don't shut down their services in the next few years.

Answer 1

Those are a lot of questions jammed into 1 there, I'll try to answer some.

As you already tagged it, TAPI is an option but not very easy to get into. TAPI normally get it's information centrally from the PBX, but in your particular case the SNOM system has the phones themselves connect to a central server to gather the information and distribute it there. You may be able to hook into a proprietary protocol.

Gathering calls on a central server to then distribute them to phones is usually done with an IVR (Interactive voice response). Channeling outside calls through it is easy but the problem with getting your call information from this point is usually you miss the internal calls.

Your website pop-up is not my area of expertise, maybe someone else could comment on the feasibility of that, but personally I would go with a task-tray style app if reliability is your highest priority.