AWS IoT Device SDK C:
MQTT
MQTT 3.1.1 client library
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Parameter to an MQTT callback function. More...
#include <iot_mqtt_types.h>
Data Fields | |
IotMqttConnection_t | mqttConnection |
The MQTT connection associated with this completed operation, incoming PUBLISH, or disconnect. More... | |
union { | |
struct { | |
IotMqttOperationType_t type | |
Type of operation that completed. | |
IotMqttOperation_t reference | |
Reference to the operation that completed. | |
IotMqttError_t result | |
Result of operation, e.g. succeeded or failed. | |
} operation | |
struct { | |
const char * pTopicFilter | |
Topic filter that matched the message. | |
uint16_t topicFilterLength | |
Length of pTopicFilter . | |
IotMqttPublishInfo_t info | |
PUBLISH message received from the server. | |
} message | |
IotMqttDisconnectReason_t disconnectReason | |
Why the MQTT connection was disconnected. | |
} | u |
Valid member depends on callback type. | |
Parameter to an MQTT callback function.
Parameter for: MQTT callback functions
The MQTT library passes this struct to a registered callback whenever an operation completes, a message is received on a topic filter, or an MQTT connection is disconnected.
The members of this struct are different based on the callback trigger. If the callback function was triggered for completed operation, the operation
member is valid. Otherwise, if the callback was triggered because of a server-to-client PUBLISH, the message
member is valid. Finally, if the callback was triggered because of a disconnect, the disconnectReason
member is valid.
For an incoming PUBLISH, the message.pTopicFilter
parameter provides the subscription topic filter that matched the topic name in the PUBLISH. Because topic filters may use MQTT wildcards, the topic filter may be different from the topic name. This pointer must be treated as read-only; the topic filter must not be modified. Additionally, the topic filter may go out of scope as soon as the callback function returns, so it must be copied if it is needed at a later time.
IotMqttConnection_t IotMqttCallbackParam_t::mqttConnection |
The MQTT connection associated with this completed operation, incoming PUBLISH, or disconnect.
MQTT API functions are safe to call from a callback for completed operations or incoming PUBLISH messages. However, blocking function calls (including IotMqtt_Wait) are not recommended (though still safe). Do not call any API functions from a disconnect callback.