receiver& connection::create_receiver(const std::string &addr, bool dynamic, handler *h)
{
    return default_session().create_receiver(addr, dynamic, h);
}
receiver connection::open_receiver(const std::string &addr, const receiver_options &opts)
{
    return default_session().open_receiver(addr, opts);
}
sender& connection::create_sender(const std::string &addr, handler *h) {
    return default_session().create_sender(addr, h);
}