Creating the ServerSocket in a separate thread?

Usually, I use N+1 threads for this : one for the ServerSocket, to avoid blocking the whole application waiting for a client to connect; and N threads to process the client’s requests, N being the size of the thread pool (I recommend using a thread pool over creating a new thread per client).

Here is an example (just coded it, you may want to have better exception management and such, but this is a minimal working example)

public class Server {

    public static void main(String[] args) {
        new Server().startServer();
    }

    public void startServer() {
        final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(10);

        Runnable serverTask = new Runnable() {
            @Override
            public void run() {
                try {
                    ServerSocket serverSocket = new ServerSocket(8000);
                    System.out.println("Waiting for clients to connect...");
                    while (true) {
                        Socket clientSocket = serverSocket.accept();
                        clientProcessingPool.submit(new ClientTask(clientSocket));
                    }
                } catch (IOException e) {
                    System.err.println("Unable to process client request");
                    e.printStackTrace();
                }
            }
        };
        Thread serverThread = new Thread(serverTask);
        serverThread.start();

    }

    private class ClientTask implements Runnable {
        private final Socket clientSocket;

        private ClientTask(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }

        @Override
        public void run() {
            System.out.println("Got a client !");

            // Do whatever required to process the client's request

            try {
                clientSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}