Controlling sending rate over UDP socket

Question

Hello,
After some NIO study, i finally managed to send and receive UDP data from a single thread. Here is my code
so far:
try {
      DatagramChannel channel = DatagramChannel.open();
      channel.configureBlocking(false);
     channel.socket().bind(localAddress);
      boolean flag = true;
      int LIMIT = 1000;
      Selector selector = Selector.open();
      channel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
      ByteBuffer buffer = ByteBuffer.allocate(4);
      int n = 0;
      int numbersRead = 0;
      while (flag) {
        selector.select();
        Set readyKeys = selector.selectedKeys();
          Iterator iterator = readyKeys.iterator();
          while (iterator.hasNext()) {
            SelectionKey key = (SelectionKey) iterator.next();
            iterator.remove();
            if (key.isReadable()) {
              buffer.clear();
              channel.read(buffer);
              buffer.flip();
              numbersRead++;
            } else if (key.isWritable()) {
              n = queue.poll();
              buffer.clear();
              buffer.putInt(n);
              buffer.flip();
              channel.write(buffer);
              System.out.println("Wrote: " + n);
             if (n == LIMIT) {
                // All packets have been written; switch to read-only mode
                key.interestOps(SelectionKey.OP_READ);
    }  // end try
    catch (IOException ex) {
      System.err.println(ex);
    }  // end catchThis thread both receives and send integers from/to my UDP echo server. Another thread acts as data generator and add data to ConcurentLinkedQueue. The sending thread poll the data from the queue and sends it.
Right now, the thread is sending at full speed.
I would like to know how i can control the sending rate ?
I would like to be able to specify a given rate like 50 packets per second, 100 packets per seconds...?
Of course i can always slow down the sending part by adding Thread.sleep(someValue) before or after sending..
but this way i am not sure what is the real rate achieved.
any advises would be welcome.
thanks
sepi
Edited by: sepi_seb on Dec 17, 2007 6:50 PM

Answer 1

hi
thanks for your reply.
I have some difficulties calculating the amount of time i need to sleep to achieve a proper sending speed.
basically it takes 16ms to send 20 requests so 1250req/s. Hoe can i regulate this accurately.
I added this kind of code in my sending part: Every 50 requests i execute this code.For some reason i get a divided by zero exception at the line marked in bold.
it happens at the second execution of this code.
     if(count == 50){
              count = 0;
              elapsedTime = System.currentTimeMillis() - startTime;
              System.out.println(elapsedTime);
              *sendingRate = (50 * 1000) / elapsedTime;*
              System.out.println("sending at:" + sendingRate + " req/s");
              if(sendingRate > speed){
                long diff = sendingRate - speed;
                long sleepTime = (diff * elapsedTime) / 50;
                try {
                  Thread.sleep(sleepTime);
                } catch (InterruptedException e) {
      }any comments are welcome
thanks
sebastien