Live voice chat in local network from mobile device to desktop

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C#

Android

network

WiFi

I need a api to integrate in my mobile application for live voice chat.
My goal is i don't need any extra hardware to manage voice chat between my employees to server room or controller PC in my local wifi network, even if internet is not working they can easily communicate in our local wifi network using my mobile application.

What I have tried:

I have try JavaScript chat plugins but it first record the voice and then send to server pc, I need live voice streaming between mobile app to my controller or server pc.