Moved to http://pubsubclient.knolleary.net/
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nick • November 14, 2013
To properly assure qos 1 delivery, the client needs to store the message until it receives the acknowledgement from the server. This allows it to resend the message if it does not get that ack.
By ‘store’, that could simply mean in memory, or in some non-volatile storage.
If it is in memory only, then it will be lost if the Arduino resets. It also uses up scarce memory.
If you have an SD card shield, that could provide non-volatile storage.
Sticking to qos 0, doing the subscribe-to-verify trick would work.
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