[Jackaudio] Voip-like application with JackAudio

Hello, I am working on a Voip-like application using JackAudio. I have used blocking API from PulseAudio and wasn't satisfied with its latency(that's why I turned to JackAudio). However, working with Jack's callback style is confusing since I do not manually create the threads and that they are implicit. My question is how do I create two separate threads with callbacks so that one thread can receive data and the other thread can send data across a network? Is there any blocking API available instead of callbacks?