Socket.accept stuck in loop

[Rob Brew]

Hi all.

I'm at a loss as i've studied the official Oracle documentation on how to handle sockets and this problem still remains:

private void initNetworking() {
        try {
            ServerSocket serverSocket = new ServerSocket(4242);
            while (true) {

                Socket clientSocket = serverSocket.accept();
                Thread t = new Thread(new ClientHandler(clientSocket));
                t.start();
                serverSocket.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

The Core class (of which the above method is call from) never exits therefore the next command in the main function cannot execute.

   public static void main(String[] args) {
        
        Board b = new Board();
        System.out.println("here");
        Core c = new Core(b);
       System.out.println("there");
        TTTCoreGui gui = new TTTCoreGui(c);
        gui.setVisible(true);
      }

"There" never gets printed.

Should i set up initNetworking as a thread?

Thread.sleep() needed.

[Paul Clapham]

Well, yeah. The line "serverSocket.accept()" is indeed waiting until a client connects. And then once that happens, it's going to accept the client and wait for the next one.

So if you don't want that code to block something else, then yes, you should run it in its own thread.

[Jeff Verdegan]

Rob Brew wrote:
Should i set up initNetworking as a thread?

AS a thread? No. But IN its own thread, yes.

If you do

while (true) {
  // stuff
}

// other stuff

Obviously, you'll never get to the "other stuff" part. It doesn't matter if the "stuff" part is socket calls or something else.

Also, you're closing the ServerSocket at every pass through the while loop. This means that only your first accept() will work, and all subsequent ones will fail.

Always close in a finally block.

ServerSocket ss = null;

try {
  ss = new ServerSocket(...);
  while(...) {
    ss.accept();
    ...
  }
}
finally {
  if (ss != null) {
    try {
      ss.close();
    }
    catch (Exception e) {
      // log it
    }
  }
}


// OR


ServerSocket ss = new ServerSocket(...);

try {
  while (...) {
      ss.accept();
      ...
  }
}
finally {
  try {
    ss.close();
  }
  catch (Exception e) {
    // log it
  }
}

[Campbell Ritchie]

Question too difficult for “beginning”. Moving thread.