BitTube::read now handles EAGAIN

        len = ::read(mReceiveFd, vaddr, size);

        err = len < 0 ? errno : 0;

    } while (err == EINTR);

    if (err == EAGAIN || err == EWOULDBLOCK) {

        // EAGAIN means that we have non-blocking I/O but there was

        // no data to be read. Nothing the client should care about.

        return 0;

    }

    return err == 0 ? len : -err;

}