This application can to send audio from device to device in local network and play it in real time.
You can adjust the Sender's audio format (mono stereo 48000 Hz 22000 Hz etc.) and adjust the buffer size on the Receiver (the larger the buffer the longer the audio delay but less loss).
How to send audio from device to device and play it in real time:
Run the application on two devices in the first case select "Sender" in the second case select "Receiver".
Select the input device in Sender the output device in the Receiver. Then enter the IP address and port of the Sender into the Receiver's application and click Connect
After that enter to Receiver ip and port of Sender and press "Connect".
If you did all this correctly sound will start playing on your second device. Else you will see message about what's wrong.

It's an open source crossplatform project you can visit github.com/Dervun/Remote_Speaker and build project on your PC.
In this case you can start the application on your computer select "Sender" on the PC "Receiver" on the Android device and play the sound from the PC to Android.
For example you can select an input device like "Stereo mix" (in Windows) start playing music video or something else on your PC and hear the sound on your Android device (or headphones inserted into it).
This trick will suit some people instead of wireless headphones.