MQTT Client: mqtt_client_ctx_cbs Struct Reference

Notifies the client application about an ACK or a response from the server. Following are the messages that are notified by the client LIB to the application.

CONNACK, PINGRSP, PUBACK, PUBCOMP, SUBACK, UNSUBACK

Parameters:

[in]

app

application to which this ACK message is targeted

See also:

mqtt_client_ctx_create

Parameters:

[in]	msg_type	Type of the MQTT messsage
[in]	msg_id	transaction identity of the message
[in]	buf	refers to contents of message and depends on msg_type
[in]	len	length of the buf

Returns:

none

Note:

The size of the buf parameter i.e len is non-zero for the SUBACK and CONNACK messages. For SUBACK the buf carries an array of QOS responses provided by the server. For CONNACK, the buf carries variable header contents. Helper macro VHB_CONNACK_RC( ) and VHB_CONNACK_SP( ) can be used to access contents provided by the server. For all other messages, the value of len parameter is zero.

The parameter msg_id is not relevant for the messages CONNACK and PINGRSP and is set to zero.

Notifies the client application about the termination of connection with the server. After servicing this callback, the application can destroy associated context if it no longer required

Parameters:

[in]

app

application whose connection got terminated

See also:

mqtt_client_ctx_create

Parameters:

[in]

cause

reason that created disconnection (LIBRARY Generated Error Codes)

Provides a PUBLISH message from server to the client application. The application can utilize the associated set of helper macros to get references to the topic and the data information contained in the message. Helper Macros for RX PUBLISH

Depending upon the QoS level of the message, the MQTT client library shall dispatch the correponding acknowlegement (PUBACK or PUBREC) to the server, thereby, relieving application of this support.

If the application completes the processing of the packet within the implementation of this callback routine, then a value of 'true' must be returned to the client LIB 'context'. The library, in this case, does not handover the packet to application and instead, frees it up on return from this routine.

If the application intends to defer the processing of the PUBLISH message to a different execution task, then it must takeover the owernship of the packet by returning a value of 'false' to the client LIB 'context. In this arrangement, the client LIB 'context' hands over the packet to the application. The responsibility of storing, managing and eventually freeing up the packet back to the pool, now, lies with the app.

Parameters:

[in]

app

application to which this PUBLISH message is targeted

See also:

mqtt_client_ctx_create

Parameters:

[in]	dup	asserted to indicate a DUPLICATE PUBLISH
[in]	qos	quality of Service of the PUBLISH message
[in]	retain	Asserted to indicate message at new subscription
[in]	mqp	Packet Buffer that holds the PUBLISH message

Returns:

true to indicate that processing of the packet has been completed and it can freed-up and returned back to the pool by the library. Otherwise, false.