How to stream audio bases on WiFi and RTSP in Android?

I want to create an Android RTSP server so that it can transfer audio from an Android device to another Android device.

This APP can select music from an SD card and transfer it to other devices that are on the same network. SO is an application RTSP Server.

I have a search RTSP Server on Android, but for Android it is not clear, or only for the Client.

I'm new to this, can someone help and give me some information for * developing an RTSP server on Android ? *

How to encode music from local? and how to transfer audio to other devices?

Thanks in advance.