Thank
you for your reply Ian.
I
was not thinking in servers sending unsolicited messages but
clients only sending messages. I mean, it would be a real
use case to have a device (temperature sensor for example)
that only wants to publish data to the broker. In that cases
it would be a waste of time/resources to have a callback for
received messages since we know that the devices shouldn’t
receive anything (actually it could be solved configuring an
empty function as messageArrived callback, but it is
estrange for me to have in my code an empty function that
simply does nothing).
I
don’t know if we are talking about the same use case.
Thank
you so much for your time.
Adrián
M.
Hi Adrian,
that was a deliberate decision on my part. If no
messageArrived callback is set, then no incoming messages can
be sent to the application. This would cause the library a
dilemma, so I felt it a good idea to insist on a
messageArrived callback being implemented.
Also, I do know that some MQTT servers can send unsolicited
messages to a client.
Ian
On 09/23/2016 10:31 AM, Moran Adrian
wrote:
Hi all,
with the current
version of C Paho client is not possible to confirm
messages delivery without setting the messageArrived
callback.
File src/MQTTAsync.c
--> Function MQTTAsync_setCallbacks()
---------------------------------------------------------------------------
if (m == NULL || ma ==
NULL || m->c->connect_state != 0)
rc = MQTTASYNC_FAILURE;
else
{
m->context = context;
m->cl = cl;
m->ma = ma;
m->dc = dc;
}
Why is needed ma
(messageArrived) callback to be set to work with dc
(deliveryComplete) callback? I will just replace if
condition by the following one:
if (m == NULL ||
m->c->connect_state !=
0)
I think that
subscription and publication are completely independent
tasks, so I don’t know if it is a bug or something I don’t
have clear enough.
Thank you so much,
Adrián M.
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--
Ian Craggs
icraggs@xxxxxxxxxx IBM United Kingdom
Paho Project Lead; Committer on Mosquitto
