Creating a Web Radio

I'd like to develop a web sample application that can send and read audio on the fly.

The idea is to develop a website with HTML5/JS. So, the admin part (in php or whatever server side language) will allow me to send audio from a mic.

Then, on the client side, the user can listen to the stream with the tag for example.

Is it possible? Did anybody use a strong (open/free) solution doing that?

Thank you,

Regards.