See above: it would be much more useful to return number of replies received, rather than number of messages sent, as that's the number we are most interested in. Otherwise, if we e.g. sent 5 messages but received 1 reply, you're essentially not telling the user how far can he index the reply pointer.
Apologies, just noticed that rte_mp_reply has nb_messages in it. So if we are getting number of replies along with reply, this API should too switch to 0/-1 on success/failure respectively, as the number of sent messages also becomes meaningless to the user.
-- Thanks, Anatoly
