Hi All, I want to use Boost ASIO as an event manager in a server which, among other things, asynchronously writes into a file. I use open() to create my file and then try to assign it to a posix::stream_descriptor object. However, the following simple code throws an "Operation not permitted" exception. int main () { boost::asio::io_service ioService; int fd = open("./asio_sample.txt", O_WRONLY | O_CREAT | O_ASYNC | O_NONBLOCK, S_IRUSR | S_IWUSR | S_IRGRP); assert(fd != -1); boost::asio::posix::stream_descriptor descriptor(ioService); descriptor.assign(fd); return 0; } I traced down the epoll_reactor::register_descriptor() where the function fails to add the descriptor to the poll list. Any idea what I am doing wrong? I would appreciate any comment. Cheers, Nader