code: public void updateBytesSent(long num) {
          Iterator<ByteBuffer> iter = buffers.iterator();
  
          while (iter.hasNext()) {
              ByteBuffer cur = iter.next();
              if (cur.hasRemaining()) {
                  break;
              }
              iter.remove();
          }
      }
docs: Indicate that some data has been flushed to the network
  @param num ignored for now. This is because each individual {@link java.nio.ByteBuffer} keeps track
  of how many of its bytes were sent