Does Paho MQTT Asynchronous C Client Buffer Received Messages? #1381
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Can someone help me with this question? It's not really clear from the documentation what happens if you block too long in the messageArrived callback. |
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The application shouldn't spend much time in any of the callbacks, including messageArrived. In general that means no blocking operations. There is a message queue for outbound messages, but not for those inbound. When the messageArrived callback is running, some of the internal client library operations will be blocked - for instance any other call to messageArrived. You can return 0 from the messageArrived callback, indicating a failure, and the callback will be reinvoked. But this is not very efficient, and is only intended for error situations. |
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The application shouldn't spend much time in any of the callbacks, including messageArrived. In general that means no blocking operations. There is a message queue for outbound messages, but not for those inbound. When the messageArrived callback is running, some of the internal client library operations will be blocked - for instance any other call to messageArrived.
You can return 0 from the messageArrived callback, indicating a failure, and the callback will be reinvoked. But this is not very efficient, and is only intended for error situations.