// SocketIoProcessor.doFlush() will reset it after write is finished
// because the buffer will be passed with messageSent event.
((ByteBuffer) writeRequest.getMessage()).mark();
synchronized (writeRequestQueue) {
writeRequestQueue.push(writeRequest);
if (writeRequestQueue.size() == 1
&& session.getTrafficMask().isWritable()) {
// Notify DatagramService only when writeRequestQueue was empty.
s.getManagerDelegate().flushSession(s);
}