1async(3)                   Library Functions Manual                   async(3)
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NAME

6       async - Asynchronous vs synchronous client applications This client
7       library supports two modes of operation. These are referred to as
8       synchronous and asynchronous modes. If your application calls
9       MQTTClient_setCallbacks(), this puts the client into asynchronous mode,
10       otherwise it operates in synchronous mode.
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12       In synchronous mode, the client application runs on a single thread.
13       Messages are published using the MQTTClient_publish() and
14       MQTTClient_publishMessage() functions. To determine that a QoS1 or QoS2
15       (see Quality of service) message has been successfully delivered, the
16       application must call the MQTTClient_waitForCompletion() function. An
17       example showing synchronous publication is shown in Synchronous
18       publication example. Receiving messages in synchronous mode uses the
19       MQTTClient_receive() function. Client applications must call either
20       MQTTClient_receive() or MQTTClient_yield() relatively frequently in
21       order to allow processing of acknowledgements and the MQTT 'pings' that
22       keep the network connection to the server alive.
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24       In asynchronous mode, the client application runs on several threads.
25       The main program calls functions in the client library to publish and
26       subscribe, just as for the synchronous mode. Processing of handshaking
27       and maintaining the network connection is performed in the background,
28       however. Notifications of status and message reception are provided to
29       the client application using callbacks registered with the library by
30       the call to MQTTClient_setCallbacks() (see MQTTClient_messageArrived(),
31       MQTTClient_connectionLost() and MQTTClient_deliveryComplete()). This
32       API is not thread safe however - it is not possible to call it from
33       multiple threads without synchronization. You can use the MQTTAsync API
34       for that.
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38Paho MQTT C Client Library      Thu Jul 22 2021                       async(3)
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