Designing a Project

I want to start a project and need some help determine the technology / set of knowledge.

The project will be running on a raspberry-pi, which already has Mopidy up and running. I want to build chrome-cast like software, but way more simpler. What it should do on the server: open a website. When a client accesses the server using a browser, it'll receive the website that the server has opened and can access links and play music (for example if the server launched youtube). I want that every client will be able to access the very same site so that if 2 clients connect to the server they will see the very same site. Also, the music needs to be played on the server and not on the client.

What I've done so far: I created a basic HTML page with the tag 'iframe' but what it did was to open the site on the client (and all the music was played on the client), also two separate clients received not the same session.

I do know to program, mostly embedded systems and low level architecture, never done something with web (but i'm a quick learner). I'm asking for some tips and technologies you recommend for me to look for implementing the project.

Thank you in advance