SocketImpl設置選項中的套接字關閉異常

Question

我試圖設置套接字的SO_KEEPALIVE時間。

我創建了一個類SocketBuilder來構建帶有SocketImpl的套接字實例。源代碼如下，

public class SocketBuilder { 

    private static SocketImpl si; 

    public static Socket createCVPSocket() throws Exception { 
     if (si == null) { 
      init(); 
     } 
     return new CSocket(si); 
    }  


    private static void init() throws SocketException { 
     @SuppressWarnings("rawtypes") 
     Constructor cons = null; 
     try { 
      cons = Class.forName("java.net.SocksSocketImpl") 
        .getDeclaredConstructor(); 
     } catch (NoSuchMethodException | SecurityException 
       | ClassNotFoundException e) { 
      throw new RuntimeException(
        "Not able to access socket implementation."); 
     } 
     cons.setAccessible(true); 
     SocketImpl si = null; 
     try { 
      si = (SocketImpl) cons.newInstance(); 
     } catch (InstantiationException | IllegalAccessException 
       | IllegalArgumentException | InvocationTargetException e) { 
      throw new RuntimeException("Not able to create instance of socket."); 
     } 
     if (si != null) { 
      si.setOption(SocketImpl.SO_KEEPALIVE, new Integer(60)); 
     } 
    } 

    private static class CSocket extends Socket { 
     protected CSocket(SocketImpl si) throws SocketException, Exception { 
      super(si); 
     } 
    } 
    public static void main(String[] args) { 
     try { 
      Socket sock = SocketBuilder.createCVPSocket(); 
      System.out.println(sock); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
    } 
} 

我得到java.net.SocketException: Socket Closed異常。如果我刪除行si.setOption(SocketImpl.SO_KEEPALIVE, new Integer(60));它工作正常。但我想設置SocketImpl.SO_KEEPALIVE。我怎樣才能設置插座的SO_KEEPALIVE？

Answer 1

有在你的代碼中的一些錯誤：

1. SocketImpl si = null;這個聲明重疊類字段只

2. setOption作品在套接字打開/連接

3. 時，你必須關閉套接字完成

   import java.lang.reflect.Constructor; 
   import java.lang.reflect.InvocationTargetException; 
   import java.net.*; 
   
   public class SocketBuilder { 
   private static SocketImpl si; 
   
   public static Socket createCVPSocket() throws Exception { 
       if (si == null) { 
        init(); 
       } 
       return new CSocket(si); 
   }  
   
   
   private static void init() throws SocketException { 
       @SuppressWarnings("rawtypes") 
       Constructor cons = null; 
       try { 
        cons = Class.forName("java.net.SocksSocketImpl") 
          .getDeclaredConstructor(); 
       } catch (NoSuchMethodException | SecurityException 
         | ClassNotFoundException e) { 
        throw new RuntimeException(
          "Not able to access socket implementation."); 
       } 
       cons.setAccessible(true); 
       si = null; 
       try { 
        si = (SocketImpl) cons.newInstance(); 
       } catch (InstantiationException | IllegalAccessException 
         | IllegalArgumentException | InvocationTargetException e) { 
        throw new RuntimeException("Not able to create instance of socket."); 
       } 
   
   } 
   
   private static class CSocket extends Socket { 
       protected CSocket(SocketImpl si) throws SocketException, Exception { 
        super(si); 
        super.bind(new InetSocketAddress("127.0.0.1", 8888)); 
   
        si.setOption(SocketImpl.SO_KEEPALIVE, Boolean.TRUE); 
       } 
   } 
   public static void main(String[] args) { 
       try { 
        Socket sock = SocketBuilder.createCVPSocket(); 
        System.out.println(sock); 
       } catch (Exception e) { 
        e.printStackTrace(); 
       } 
   } 
   

   }

Answer 2

如果你看一下AbstractPlainSocketImpl#setOption方法的源代碼，

public void setOption(int opt, Object val) throws SocketException { 
     if (isClosedOrPending()) { 
      throw new SocketException("Socket Closed"); 
     } 
// Rest of the code removed for brevity 
} 

你可以看到有設置選項前的isClosedOrPending檢查。

/* 
* Return true if already closed or close is pending 
*/ 
public boolean isClosedOrPending() { 
    /* 
    * Lock on fdLock to ensure that we wait if a 
    * close is in progress. 
    */ 
    synchronized (fdLock) { 
     if (closePending || (fd == null)) { 
      return true; 
     } else { 
      return false; 
     } 
    } 
} 

在你的情況，因爲你只是創建一個插座，它不會有任何相關的FD。這就是你得到這個錯誤的原因。