JavaFX application not responding when found ServerSocket.accept() method

Question

I create javafx application and have to combine it with ServerSocket, but when I use function accept of ServerSocket the application is black out. what I expected is to let the application wait until there a Socket connect and run the next method. I have no idea what happen but when I comment the line of ServerSocket.accept() out it work just fine. I have try to read api doc of ServerSocket but I found no help in it or maybe I just too dull for it.

Main

package test;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.net.ServerSocket;


public class ProblemTest extends Application {
    public static void main(String[] args) throws Exception{
        launch(args);
    }
    public void start(Stage primaryStage)throws Exception{
        FXMLLoader loader = new FXMLLoader(getClass().getResource("test.fxml"));
        Parent root= loader.load();
        Scene scene=new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
        ServerSocket server=new ServerSocket(8000);
        server.accept();

    }
}

Fxml file:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.layout.VBox?>

<VBox prefHeight="400.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <MenuBar>
        <menus>
          <Menu mnemonicParsing="false" text="File">
            <items>
                  <MenuItem mnemonicParsing="false" text="Clear" />
              <MenuItem mnemonicParsing="false" text="Close" />
            </items>
          </Menu>
        </menus>
      </MenuBar>
      <TextArea prefHeight="377.0" prefWidth="640.0" />
   </children>
</VBox>
```

Answer 1

server.accept()

blocks application thread, you need to invoke accept() in another thread.

new Thread(() -> {
    ... new ServerSocket(8000).accept();
}).start()