Java - 重新加載類時關閉套接字

Question

因此，我正在爲IRC服務器，並且我添加了一個配置屏幕，您可以在其中編輯它正在使用的端口，但我必須重新調整Listen類效果，所以我有這個在我的配置類：

Listen.closePorts(); 
new Listen(); 

這裏是我聽類：

package server.network; 

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.net.ServerSocket; 
import java.net.Socket; 

import server.Server; 
import server.gui.GUIMain; 

public class Listen { 
    private static Socket socket = null; 
    private int port; 

    public Listen() { 
     try { 
      port = Server.listenPort; 
      @SuppressWarnings("resource") 
      ServerSocket serverSocket = new ServerSocket(port); 
      GUIMain.jta.append("\nServer Started and listening for messages on port " + port + ".\n"); 

      while(true) { 
       socket = serverSocket.accept(); 
       InputStream is = socket.getInputStream(); 
       InputStreamReader isr = new InputStreamReader(is); 
       BufferedReader br = new BufferedReader(isr); 
       String msg = br.readLine(); 
       GUIMain.jta.append("Received message from client: " + msg + "\n"); 
      } 
     } catch (Exception e) { 
      GUIMain.jta.append("Port " + port + " already in use!\n"); 
     } finally { 
      try { 
       socket.close(); 
      } catch(Exception e) { } 
     } 
    } 

    public static void closePorts() { 
     try { 
      socket.close(); 
      GUIMain.jta.append("Server closed\n"); 
     } catch (IOException e) { } 
    } 
} 

當我開始運行這一類的應用，與指定的端口打開插座，但是當我嘗試關閉這個端口時：

public static void closePorts() { 
    try { 
     socket.close(); 
     GUIMain.jta.append("Server closed\n"); 
    } catch (IOException e) { } 
} 

它掛在socket.close();

如果我評論Listen.closePorts();並嘗試重新加載類和離開插座打開它是掛起或運行catch()如果端口是相同的，因爲這是在港口使用。

這麼久以來，我怎麼才能重新教育班級和使用新的端口之前關閉插座？

下面是完整的例外是trows：

java.lang.NullPointerException 
    at server.network.Listen.closePorts(Listen.java:44) 
    at server.gui.GUISettings.actionPerformed(GUISettings.java:86) 
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) 
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) 
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) 
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source) 
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source) 
    at java.awt.Component.processMouseEvent(Unknown Source) 
    at javax.swing.JComponent.processMouseEvent(Unknown Source) 
    at java.awt.Component.processEvent(Unknown Source) 
    at java.awt.Container.processEvent(Unknown Source) 
    at java.awt.Component.dispatchEventImpl(Unknown Source) 
    at java.awt.Container.dispatchEventImpl(Unknown Source) 
    at java.awt.Component.dispatchEvent(Unknown Source) 
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) 
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) 
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) 
    at java.awt.Container.dispatchEventImpl(Unknown Source) 
    at java.awt.Window.dispatchEventImpl(Unknown Source) 
    at java.awt.Component.dispatchEvent(Unknown Source) 
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
    at java.awt.EventQueue.access$200(Unknown Source) 
    at java.awt.EventQueue$3.run(Unknown Source) 
    at java.awt.EventQueue$3.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
    at java.awt.EventQueue$4.run(Unknown Source) 
    at java.awt.EventQueue$4.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
    at java.awt.EventQueue.dispatchEvent(Unknown Source) 
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.run(Unknown Source) 

Answer 1

socket變量只有在客戶端發出請求後纔會分配。如果您在此之前致電closePorts()，程序仍會等待socket = serverSocket.accept();，並且socket.close()將拋出NullPointerException，因爲socket仍然爲空。對於ServerSocket.accept（）的描述，請參閱http://docs.oracle.com/javase/7/docs/api/java/net/ServerSocket.html#accept()。

Answer 2

沒有提供一個直接的解決方案，但沒有引發異常，因爲你的代碼正在吞噬它們。空的抓塊從來都不是好習慣。至少，使用e.printStackTrace（）打印捕獲到的異常的堆棧跟蹤

Answer 3

這裏沒有類重新加載，也不需要關閉現有客戶端接受的套接字。只需關閉ServerSocket並在新端口上重新創建即可。