Server for web game and android game

Me and my few colleagues have a project which main goal is to create a game as an web app and android app. Our idea was to create server, which would handle all the logic of the games and store data of the users, so the clients would only show GUI and interact with the player. Unfortunatelly all of us are mainly c++ programmers and we only have experience in writing simple desktop apps.

And because of that we wanted to do it in such way, that we could easily implement multithreaded server with Qt library, that would catch messages from clients, parse them, pass them to logic, and would response. It would be similiar with clients, as they would need to catch servers messages and react to them as well as they would need to send messages to server with users requests.

Android client would be implemented in java of course, but most of the our hesitations regards web client.

We would be very grateful for your opinions and advices on this matter. What lanugages and frameworks should we use to make it work. Also I'd like to mention that we would like to implement server in c++, because we would like to learn how servers work on lower levels.