java - SocketImpl Setoption 中的套接字关闭异常

Question

我正在尝试设置套接字的SO_KEEPALIVE时间。

我创建了一个类 SocketBuilder 来使用 SocketImpl 构建套接字实例。源代码如下，

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();
        }
    }
}

我收到 java.net.SocketException: Socket Closed 异常。如果我删除行 si.setOption(SocketImpl.SO_KEEPALIVE, new Integer(60)); 则它可以正常工作。但我想设置 SocketImpl.SO_KEEPALIVE 。如何设置套接字的SO_KEEPALIVE？

Answer 1

您的代码中存在一些错误:

1. SocketImpl si = null; 此声明与您的类字段重叠

2. setOption 仅在套接字打开/连接时有效

3. 完成后必须关闭套接字

   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();
       }
   }
   

   }