Creating the ServerSocket in a separate thread?

Question

I have a problem with using a ServerSocket in my application.

I'm creating the ServerSocket in the constructor of my application. The constructor of the socket calls the accept() method to wait for a client to connect.

The problem is that the accept() method is freezing my whole application until a client connects. So I would like to ask if there's an alternative to creating the whole ServerSocket in a separate thread, that the constructor of the ServerSocket and its accept() method is called beside my main application?

Edit:

Thanks to Olivier for the advice, putting the .accept into a runnable and creating a threadpool to handle the clientconnections.

Thats my code right now:

  public void start(){

      final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(10);

      Runnable serverTask = new Runnable() {
          @Override
          public void run() {

              try {
                  serverSocket = new ServerSocket(port);

                  while (true) {
                      Socket clientSocket = serverSocket.accept();
                      objectout = new ObjectOutputStream(clientSocket.getOutputStream());
                      clientProcessingPool.submit(new ClientTask(clientSocket,objectout)); 
                  }
              } catch (IOException e) {
                  System.err.println("Accept failed.");
              }

          }
      };

Everythings running fine! Thanks!

Answer 1

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();
            }
        }
    }

}