The qnx_reply function is a wrap of the C function Reply. Any message that you receive using the qnx_receive function should be replied to. This function should only be used if you are also using qnx_receive. The event handling functions next_event, next_event_nb, and PtMainLoop are the preferred choice for Gamma programs since that automatically handle receiving, replying, and signal, timer, Cascade DataHub events, and Photon messages.
The errno possile values for this function are:
EAGAIN Out of queue packets to network manager
EFAULT Invalid message
EINTR Function call interrupted by signal
EINVAL invalud virtual circuit buffer
ENOMEM not enough memory for operation
ESRCH the process ID does not exist