I'm not guessing anymore. I proved it to myself a while back, another
poster also acknowledged that shutdown calls work, and now I took a
saturday morning off to prove my point. You fail to acknowledge that
the shutdown() calls can work and demonstratably Channel.close()
sometimes does not. I believe the shutdown() calls are clearer -
certainly from a JavaDoc standpoint that is true.  Regardless, here's
the proof.

The code below is taken from the bug report link above - I only changed
the package and one print statement after my code in the finally block.
My system is Suse Pro 9.2 Linux, using the default jvm
/usr/lib/jvm/java-1.4.2-sun-1.4.2.05 . The default smtp server is
postfix, which by default only accepts connections from localhost.

Conclusions:

- Channel.close() does not work aa the bug report stated
- shutdownOutput() works just fine ;-) , ie via 'netstat -an | grep
CLOSE_WAIT'
- without socket.close() , isConnected() return true always, with
socket.close() about half the time the code returns false, but as
Gordon eloquently once said:

- isConnected() and isInputShutdown() cannot be relied upon to say
   anything meaningful about the state of the actual connection.

I put some simple System.currentTimeMillis() in to profile - care to
take the pepsi challege with selectNow() ?

Don't bogart - I mean it is good stuff man ;-).

Best likewise,
iksrazal

package com.whitezone;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.channels.SocketChannel;
import java.util.StringTokenizer;

// Test case code for file descriptor leak.
// The following should produce somewhere near 150 sockets in
CLOSE_WAIT state.
//
// The problem appears to be in
sun.nio.ch.SocketAdapter.SocketInputStream.read(ByteBuffer);
//

public class TestClose implements Runnable {

   public static final String SMTP_HOSTNAME = "localhost";

    public void run()
    {
       InetSocketAddress sockAddr = new
InetSocketAddress(SMTP_HOSTNAME, 25);
        SocketChannel sChannel = null;
        Socket socket = null;
        try
        {
            sChannel = SocketChannel.open();
            sChannel.connect(sockAddr);

           //  I've noticed that if I remove this line the problem no
longer happens
            sChannel.socket().setSoTimeout(5000);

            socket = sChannel.socket();

            BufferedReader lineRdr = new BufferedReader(new
InputStreamReader(socket.getInputStream()));

            String result = null;
            do
            {
               // before performing the first readline the channel is
unregistered
                System.err.println("before first readline: isOpen =
"+sChannel.isOpen()+" isRegistered="+sChannel.isRegistered());

                result = lineRdr.readLine();
                System.err.println("<- "+result);

               // after performing it is registered.
                System.err.println("after first readline: isOpen =
"+sChannel.isOpen()+" isRegistered="+sChannel.isRegistered());

            } while(result != null && result.length() > 0 &&
result.matches("^[1-5][0-9]{2}-"));

            if(result == null || result.length() == 0)
            {
                System.err.println("Received truncated response from SMTP server "
+ sockAddr.getHostName());
                return;
            }

            // Tokenize the last line result
            //
            StringTokenizer t = new StringTokenizer(result);
            int rc = Integer.parseInt(t.nextToken());
            if(rc != 220) return;

            //
            // Send the QUIT command causing the server side to close its end of
the connection
            //
            String cmd = "QUIT\r\n";
            socket.getOutputStream().write(cmd.getBytes());
            System.err.println("-> "+cmd);
            do
            {
                result = lineRdr.readLine();
                System.err.println("<- "+result);
            } while(result != null && result.length() > 0 &&
result.matches("^[1-5][0-9]{2}-"));

            if(result == null || result.length() == 0)
            {
                System.err.println("Received truncated response from SMTP server "
+ sockAddr.getHostName());
                return;
            }

        }
       catch (Exception e) {
           e.printStackTrace();
       }
        finally
        {
           try {

               System.err.println("before close: isOpen =
"+sChannel.isOpen()+" isRegistered="+sChannel.isRegistered());

               System.err.println("Closing SMTP socket channel
"+sChannel);
               System.err.println("channel.socket().isConnected = "+
sChannel.socket().isConnected());
               if (sChannel != null) {
                   //sChannel.close();
                       long start = System.currentTimeMillis();
                       System.currentTimeMillis();
                       Socket socket_close = sChannel.socket();
                       // by socket_close.shutdownOutput() itself,
CLOSE_WAIT issue fixed
                       socket_close.shutdownOutput();
                       // with socket_close.close() , isConnected
returns false sometimes
                       socket_close.close();
                       long end = System.currentTimeMillis();
                   System.err.println("Closed SMTP socket channel
"+sChannel+", Execution time was "+(end-start)+" ms.");

                   // The socket is still connected here.
                   System.err.println("\n\nAFTER shutdownOutput
channel.socket().isConnected = "+sChannel.socket().isConnected());
               }
           }
           catch (Exception e) {
              System.err.println("Exception on close:");
              e.printStackTrace();
           }
        }

        return;
    }

    public static void main(String[] args) {
       TestClose test = new TestClose();
       for(int i = 0; i < 150; i++) {
        // this bug seems only to appear if different threads are
reading the channels
           Thread thread = new Thread(test);
           thread.start();
           try {thread.join(); } catch(InterruptedException e) {   }
       }

       System.err.println("Going to sleep.... run netstat -an | grep
CLOSE_WAIT ");
       while(true) {
           try { Thread.sleep(10000); } catch(InterruptedException e) {}
       }
    }
}