I attached simple example for streaming audio from B4A to B4J over internet using MQTT.
Enjoy without limitations of Server/Client problems over internet such as ISP block.
You can use this approach to create a lot of things such as Radio station, voice call, etc ...
I posted a thread long ago about the audio/video calling over the internet. Here is a simple example of how you can call almost (will discuss below) realtime.
Why only a simple audio calling example while I said that I will post both audio and video calling examples?