FULL PRODUCT VERSION :
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) Server VM (build 1.6.0_03-b05, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
1. Linux hostname 2.4.21-27.ELsmp #1 SMP Wed Dec 1 21:59:02 EST 2004 i686 i686 i386 GNU/Linux

2. HP-UX hostname2 B.11.23 U ia64 2718609364 unlimited-user license


A DESCRIPTION OF THE PROBLEM :
The NIO selector wakes up infinitely in this situation..

0. server waits for connection
1. client connects and write message
2. server accepts and register OP_READ
3. server reads message and remove OP_READ from interest op set
4. client close the connection
5. server write message (without any reading.. surely OP_READ is not set)
6. server's select wakes up infinitely with return value 0


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
First run the TestServer.
 java -cp . TestServer 7777

In another console, run the TestClient
 java -cp . TestClient 192.168.1.34 7777



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expected nothing will happen (the selector should not woke up).

ACTUAL -
In windows, it worked as I expected but, in Linux and HP/UX the selector goes into the infinite loop.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
TestServer.java

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.util.*;
import java.util.logging.*;

public class TestServer {
    private static final long SLEEP_PERIOD = 5000L; // 5 seconds
    private static final int BUFFER_SIZE = 8192;
    private int port;

    public TestServer(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws Throwable {
if (args.length < 1) {
System.err.println("Usage : java TestServer <port>");
System.exit(0);
}

        new TestServer(Integer.parseInt(args[0])).start();
    }

    public void start() throws Throwable {
ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);

        ServerSocketChannel serverChannel = ServerSocketChannel.open();
        serverChannel.configureBlocking(false);
        ServerSocket server = serverChannel.socket();
        server.bind(new InetSocketAddress(port));

        Selector selector = Selector.open();
        serverChannel.register(selector, SelectionKey.OP_ACCEPT);
        SocketChannel clientChannel = null;

        System.out.println("0. SERVER STARTED TO LISTEN");
        boolean writeNow = false;

while (true) {
try {
// wait for selection
int numKeys = selector.select();

                if (numKeys == 0) {
                    System.err.println("select wakes up with zero!!!");
                }

Iterator it = selector.selectedKeys().iterator();
while (it.hasNext()) {
SelectionKey selected = (SelectionKey) it.next();
int ops = selected.interestOps();

                    try {
                        // process new connection
                        if ((ops & SelectionKey.OP_ACCEPT) != 0) {
                            clientChannel = serverChannel.accept();
                            clientChannel.configureBlocking(false);

                            // register channel to selector
                            clientChannel.register(selector, SelectionKey.OP_READ, null);
                            System.out.println("2. SERVER ACCEPTED AND REGISTER READ OP : client - " + clientChannel.socket().getInetAddress());
                        }

                        if ((ops & SelectionKey.OP_READ) != 0) {
                            // read client message
                            System.out.println("3. SERVER READ DATA FROM client - " + clientChannel.socket().getInetAddress());
                            readClient((SocketChannel) selected.channel(), buffer);

                            // deregister OP_READ
                            System.out.println("PREV SET : " + selected.interestOps());
                            selected.interestOps(selected.interestOps() & ~SelectionKey.OP_READ);
                            System.out.println("NEW SET : " + selected.interestOps());

                            Thread.sleep(SLEEP_PERIOD * 2);
                            new WriterThread(clientChannel).start();
                        }

                    } finally {
                        // remove from selected key set
                        it.remove();
                    }
}
} catch (IOException e) {
System.err.println("IO Error : " + e.getMessage());
}
}
    }


    public void readClient(SocketChannel channel, ByteBuffer buffer) throws IOException {
        try {
            buffer.clear();

            int nRead = channel.read(buffer);

            if (nRead < 0) {
                channel.close();
                return;
            }

            if (buffer.position() != 0) {
                int size = buffer.position();
                buffer.flip();
                byte[] bytes = new byte[size];
                buffer.get(bytes);
                System.out.println("RECVED : " + new String(bytes));
            }
        } catch (IOException e) {
            System.err.println("IO Error : " + e.getMessage());
            channel.close();
        }
    }

    static class WriterThread extends Thread {
        private SocketChannel clientChannel;
        public WriterThread(SocketChannel clientChannel) {
            this.clientChannel = clientChannel;
        }

        public void run() {
            try {
                writeClient(clientChannel);
                System.out.println("5. SERVER WRITE DATA TO client - " + clientChannel.socket().getInetAddress());
            } catch (IOException e) {
                System.err.println("5. SERVER WRITE DATA FAILED : " + e);
            }
        }

        public void writeClient(SocketChannel channel) throws IOException {
            try {
                ByteBuffer buffer = ByteBuffer.wrap("zwxydfdssdfsd".getBytes());
                int total = buffer.limit();

                int totalWrote = 0;
                int nWrote = 0;

                while ((nWrote = channel.write(buffer)) >= 0) {
                    totalWrote += nWrote;
                    if (totalWrote == total) {
                        break;
                    }
                }
            } catch (IOException e) {
                System.err.println("IO Error : " + e.getMessage());
                channel.close();
            }
        }


    }
}


TestClient.java

import java.util.logging.*;
import java.io.*;
import java.net.*;

public class TestClient {
    private static final long SLEEP_PERIOD = 5000L; // 5 seconds
    private String host;
    private int port;

    public TestClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public static void main(String[] args) throws Throwable {
if (args.length < 2 || args[0].equals("127.0.0.1") || args[0].equals("localhost")) {
System.err.println("Usage : java TestClient <host name> <port> (host name should not be localhost)");
System.exit(0);
}

        new TestClient(args[0], Integer.parseInt(args[1])).start();
    }

    public void start() throws Throwable {
        Socket socket = new Socket(host, port);

BufferedReader in = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
PrintWriter out = new PrintWriter(
new OutputStreamWriter(socket.getOutputStream()),
true /* auto flush */);

        out.println("abcdef");

        System.out.println("1. CLIENT CONNECTED AND WROTE MESSAGE");

        Thread.sleep(SLEEP_PERIOD);

// socket.shutdownOutput();
        socket.close();

        System.out.println("4. CLIENT SHUTDOWN OUTPUT");

        Thread.sleep(SLEEP_PERIOD * 3);
    }
}


---------- END SOURCE ----------