MQTT_DeserializePublish

MQTTStatus_t MQTT_DeserializePublish( const MQTTPacketInfo_t * pIncomingPacket,
                                      uint16_t * pPacketId,
                                      MQTTPublishInfo_t * pPublishInfo,
                                      MQTTPropBuilder_t * propBuffer,
                                      uint32_t maxPacketSize,
                                      uint16_t topicAliasMax );

Deserialize an MQTT PUBLISH packet.

Parameters

[in]	pIncomingPacket	MQTTPacketInfo_t containing the buffer.
[out]	pPacketId	The packet ID obtained from the buffer.
[out]	pPublishInfo	Struct containing information about the publish.
[in]	propBuffer	Buffer to hold the properties.
[in]	maxPacketSize	Maximum packet size.
[in]	topicAliasMax	Maximum topic alias specified in the CONNECT packet.

Returns

• MQTTBadParameter if invalid parameters are passed
• MQTTBadResponse if invalid packet is read
• MQTTSuccess otherwise.

Example

// TransportRecv_t function for reading from the network.
int32_t socket_recv(
     NetworkContext_t * pNetworkContext,
     void * pBuffer,
     size_t bytesToRecv
);
// Some context to be used with the above transport receive function.
NetworkContext_t networkContext;
 
// Other variables used in this example.
MQTTStatus_t status;
MQTTPacketInfo_t incomingPacket;
MQTTPublishInfo_t publishInfo = { 0 };
MQTTPropBuilder_t propBuffer ;
uint16_t packetId;
uint32_t maxPacketSize = pContext->connectionProperties.maxPacketSize;
uint16_t topicAliasMax = pContext->connectionProperties.topicAliasMax;
 
int32_t bytesRecvd;
// A buffer to hold remaining data of the incoming packet.
uint8_t buffer[ BUFFER_SIZE ];
 
// Populate all fields of the incoming packet.
status = MQTT_GetIncomingPacketTypeAndLength(
     socket_recv,
     &networkContext,
     &incomingPacket
);
assert( status == MQTTSuccess );
assert( incomingPacket.remainingLength <= BUFFER_SIZE );
bytesRecvd = socket_recv(
     &networkContext,
     ( void * ) buffer,
     incomingPacket.remainingLength
);
incomingPacket.pRemainingData = buffer;
 
// Deserialize the publish information if the incoming packet is a publish.
if( ( incomingPacket.type & 0xF0 ) == MQTT_PACKET_TYPE_PUBLISH )
{
     status = MQTT_DeserializePublish( &incomingPacket, &packetId, &publishInfo,
                                       &propBuffer, maxPacketSize, topicAliasMax );
     if( status == MQTTSuccess )
     {
         // The deserialized publish information can now be used from `publishInfo`.
     }
}