Why do I get a CancelledKeyException?
<p>Why do I get an error of Cancelled Key Exception? Can anyone please help me? What part of the code of the client went wrong?</p>

<pre><code>java.nio.channels.CancelledKeyException
at sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:73)
at sun.nio.ch.SelectionKeyImpl.interestOps(SelectionKeyImpl.java:82)
at viaNIO.clientasync2.write(clientasync2.java:130)
at viaNIO.clientasync2.run(clientasync2.java:53)
at java.lang.Thread.run(Thread.java:745)

java.nio.channels.CancelledKeyException
at sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:73)
at sun.nio.ch.SelectionKeyImpl.readyOps(SelectionKeyImpl.java:87)
at java.nio.channels.SelectionKey.isReadable(SelectionKey.java:289)
at viaNIO.clientasync2.run(clientasync2.java:55)
at java.lang.Thread.run(Thread.java:745)
</code></pre>

<p>Here is the code for the Client:</p>

<pre><code>        while (!Thread.interrupted()) {

            selector.select();

            Iterator&lt;SelectionKey&gt; keys = selector.selectedKeys().iterator();

            while (keys.hasNext()) {
                SelectionKey key = keys.next();
                keys.remove();

                if (key.isValid()) {
                    if (key.isConnectable()) {
                        System.out.println("Connected to the server");
                        connect(key);
                    }
                    if (key.isWritable()) {
                        System.out.println("Writing to the server");
                        write(key);
                    }
                    if (key.isReadable()) {
                        System.out.println("Reading from the server");
                        read(key);
                    }
                }
            }
        }
</code></pre>

<p>Here is the updated Code:</p>

<pre><code>   while (!Thread.interrupted()) {

            selector.select();

            Iterator&lt;SelectionKey&gt; keys = selector.selectedKeys().iterator();

            while (keys.hasNext()) {
                SelectionKey key = keys.next();
                keys.remove();

                if (key.isValid() &amp;&amp; key.isConnectable()) {
                    connect(key);
                } else {
                    if (key.isValid() &amp;&amp; key.isWritable()) {
                        System.out.println("Writing to the server");
                        write(key);
                    }
                    if (key.isValid() &amp;&amp; key.isReadable()) {
                        System.out.println("Reading from the server");
                        read(key);
                    }
                }
            }
        }
</code></pre>

<p>This is also my code for the write method</p>

<pre><code> private void write(SelectionKey key) throws IOException {
    SocketChannel socket = (SocketChannel) key.channel();
    RandomAccessFile aFile = null;
    try {
        File f = new File("D:/test.rar");
        aFile = new RandomAccessFile(f, "r");
        ByteBuffer buffer = ByteBuffer.allocate(300000000);

        FileChannel inChannel = aFile.getChannel();
        while (inChannel.read(buffer) &gt; 0) {
            buffer.flip();
            socket.write(buffer);
            buffer.clear();
        }
        aFile.close();
        socket.close();
        inChannel.close();
        Thread.sleep(1000);

        key.interestOps(SelectionKey.OP_READ);
    } catch (Exception e) {
        e.printStackTrace();
    }
}
</code></pre>

<p>The code for the read method</p>

<pre><code>  private void read(SelectionKey key) throws IOException {
    SocketChannel channel = (SocketChannel) key.channel();
    ByteBuffer readBuffer = ByteBuffer.allocate(1000);
    readBuffer.clear();
    int length;
    try {
        length = channel.read(readBuffer);
    } catch (IOException e) {
        System.out.println("Reading problem, closing connection");
        key.cancel();
        channel.close();
        return;
    }
    if (length == -1) {
        System.out.println("Nothing was read from server");
        channel.close();
        key.cancel();
        return;
    }
    readBuffer.flip();
    byte[] buff = new byte[1024];
    readBuffer.get(buff, 0, length);
    System.out.println("Server said: " + new String(buff));
    if (readCnt != 1) {
        key.interestOps(SelectionKey.OP_WRITE);
        readCnt++;
    } else {
        key.cancel();
        close();
    }
}
</code></pre>

<p>The code for the connect method</p>

<pre><code> private void connect(SelectionKey key) throws IOException {
    SocketChannel channel = (SocketChannel) key.channel();
    if (channel.isConnectionPending()) {
        channel.finishConnect();
    }
    channel.configureBlocking(false);
    channel.register(selector, SelectionKey.OP_READ);
}
</code></pre>