what are the concepts (on server) used in designing a multiplayer game like QuizUp?

Question

I am looking forward for designing a real time multiplayer game like QuizUp in android. I understand the UI and the database part of it , but I am not able to gauge the complexity involved to write the server logic.

So some features that I am looking for are as follows :

1. 2 registered users randomly connect with each other in the app
2. They compete with each other to answer a set of 5 ques in 1 min
3. The one who answers more accurately in less time gets some points

Can some one please highlight the building blocks on the Server that will be required to achieve the above use cases?

Probable building blocks/ modules that i can think of are :

1. Authentication
2. Session Management

please point out any missing block on the Server not Database and UI from your experience Thanks

Answer 1

I think what you need in server is a real-time web application framework though I've never played QuizUp. With such stuff, you can easily deal with your business logic.

The following pseudo code is written in Cettia. It's a real-time web application framework I authored but since only Java server and JavaScript client are provided, you can't use it for Android for now. Neverthelss, I think it would help you when writing your business logic roughly and finding such framework in terms of evaluating features you need.

Server server = new DefaultServer();
Queue<ServerSocket> waitings = new ConcurrentLinkedQueue<>();
server.onsocket(socket -> {
    // Find the counterpart from the waiting queue
    // This is #1
    ServerSocket counterpart = waitings.poll();
    // If no one waits, adds the socket to the queue
    // Remaining logic will be executed when other socket, the socket's counterpart, is connected
    if (counterpart == null) {
        waitings.offer(socket);
        // Make sure evicts the socket when it's closed
        socket.onclose(() -> waitings.remove(socket));
        return;
    }

    // Now we have two registered users - socket and counterpart

    // Find a quiz which is a set of 5 questions from database or somewhere
    // Assumes quiz has a randomly generated id property
    Quiz quiz = Quiz.random();
    // Create a report to evaluate socket and counterpart's answer
    Report report = new Report();

    // Make a group for socket and counterpart for convenience
    socket.tag(quiz.id());
    counterpart.tag(quiz.id());

    // Find a group whose name is quiz.id(), one we've just created
    server.byTag(quiz.id())
    // and send the quiz to sockets in the group
    .send("quiz", quiz)
    // and add an event listener which will be called by each client
    // This is #2
    .on("quiz", qa -> {
        // Every time (total 5 times) client answers to each question, 
        // this listener will be executed and 'qa' contains information about question and answer

        // Evaluates if answer is right
        boolean right = Quiz.evaluate(qa.question(), qa.answer());
        // Adds a final information to the report
        report.add(qa.user(), qa.question(), qa.answer(), right);
    });

    // Initiate timeout timer
    new Timer().schedule(() -> {
        // Notifies socket and counterpart of timeout
        server.byTag(quiz.id()).send("timeout");
        // It's time to evalute the report which contains a result of this game
        // Analyze who answers more accurately in less time and give him/her some points
        // This is #3
        report...
    }, 60 * 1000).run();
});