lightning <>
Thu, 31 Jan 2008 21:09:28 -0800 (PST)
I use a selector to manage the unblocking DatagramChannel,
When I got the event that I can read from the channel
I call this method.

What I wanna know is - Is this method perform an I/O operation
at lower-layer or just copy bits from a place in the memory.

If it is the former, do I need to use multithread to invoke receive()
to make better performance???

this is part of my code:

            selector =;
            SelectionKey key = channel.register(selector, channel.validOps());

            while (run) {


                if (key.isValid() && key.isReadable()) {

                    ByteBuffer buffer = ByteBuffer
                    InetSocketAddress sock = (InetSocketAddress) channel
                    if (sock == null)
          "received No." + receivedDatagramCount
                            + " datagram");
                    String ip = sock.getAddress().getHostAddress();
                    int port = sock.getPort();
                    if (!Crypt.decrypt(buffer.array(), buffer.position())) {
                        log.warn("checksum error!");

                    P2IHeaderInfo header = P2IHeaderInfo.getInstance(buffer);

                    DispatchData data = new DispatchData(header, buffer, ip,
                            port, receivedDatagramCount);
                    Task task = new Task(Task.DISPATCH, data);
                if (key.isValid() && key.isWritable()) {

                    for(ToSendData data=resps.poll();data != null;data=resps.poll())
                                    String ip = data.getIp();
                        int port = data.getPort();
                        ByteBuffer buffer = data.getBuffer();
                        Crypt.encrypt(buffer.array(), buffer.remaining());
                        byte[] x = new byte[buffer.remaining()];
                        System.arraycopy(buffer.array(), 0, x, 0, buffer
              "Server sends No." + sendDatagramCount
                                + " datagram: ");
                        channel.send(buffer, new InetSocketAddress(ip, port));
                // }

        } catch (Exception ex) {
        } finally {
            if (selector != null) {
                try {
                } catch (IOException e) {
                    // TODO Auto-generated catch block
            if (channel != null) {
                try {
                } catch (IOException e) {
                    // TODO Auto-generated catch block

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