[paho-dev] MQTT C asynchronous token

[Frank Pagliughi <fpagliughi@xxxxxxxxxxxxxx>]

Hello Ian, and all,

I'm trying to wrap up the next rev of the C++ library, and have one nagging issue that I believe I inquired about last time. In the C library, the MQTTAsync_send() and MQTTAsync_sendMessage() functions claim:

An MQTTAsync_token is issued when this function returns successfully.

I can't find how to get this MQTTAsyncToken value until the callback which happens after the message is delivered.

The problem is that, like the Java client, the C++ client has a publish() function which returns a token, and that token is supposed to know the message ID of the outgoing packet. It is reported via:

int     itoken::get_message_id();

So, to implement this I need the Message ID (MQTTAsyncToken) as soon as the message is queued - before returning from the publish() function.

It seems that the latest version of the ...err... asynchronous mode of the synchronous library has everything I would need to publish messages, since the publish functions take a pointer to an MQTTClient_deliveryToken

int MQTTClient_publish(MQTTClient handle, char *topicName, int payloadlen,
                       void *payload, int qos, int retained,
                       MQTTClient_deliveryToken *dt)

That would be perfect!  I would switch over to the synchronous library, but there are not corresponding asynchronous  versions of connect() and disconnect().

If those existed, I (we?) wouldn't need the asynchronous library at all.

Thanks,
Frank