IotMqtt_GetIncomingMQTTPacketTypeAndLength

Extract MQTT packet type and length from incoming packet.

IotMqttError_t IotMqtt_GetIncomingMQTTPacketTypeAndLength( IotMqttPacketInfo_t * pIncomingPacket,
                                                           IotMqttGetNextByte_t getNextByte,
                                                           IotNetworkConnection_t pNetworkConnection );

Parameters

[in,out]	pIncomingPacket	Pointer to IotMqttPacketInfo_t structure where type, remaining length and packet identifier are stored.
[in]	getNextByte	Pointer to platform specific function which is used to extract type and length from incoming received stream (see example ).
[in]	pNetworkConnection	Pointer to platform specific network connection which is used by getNextByte to receive network data

Returns

IOT_MQTT_SUCCESS on successful extraction of type and length, IOT_MQTT_BAD_RESPONSE on failure.

Note

This call is part of serializer API used for implementing light-weight MQTT client.

Example

// Example code below shows how to implement getNextByte function with posix sockets.
// Note: IotMqttGetNextByte_t typedef IotMqttError_t (* IotMqttGetNextByte_t)( IotNetworkConnection_t pNetworkContext,
//                                              uint8_t * pNextByte );
// Note: It is assumed that socket is already created and connected,

IotMqttError_t getNextByte( IotNetworkConnection_t pContext,
                          uint8_t * pNextByte )
{
     int socket = ( int ) ( *pvContext );
     int receivedBytes;
     IotMqttError_t result;

     receivedBytes = recv( socket, ( void * ) pNextByte, sizeof( uint8_t ), 0 );

     if( receivedBytes == sizeof( uint8_t ) )
     {
         result = IOT_MQTT_SUCCESS;
     }
     else
     {
         result = IOT_MQTT_TIMEOUT;
     }

      return result;
}

// Example below shows how IotMqtt_GetIncomingMQTTPacketTypeAndLength() is used to extract type
// and length from incoming ping response.
// xMQTTSocket here is posix socket created and connected to MQTT broker outside of this function.
void getTypeAndLengthFromIncomingMQTTPingResponse( int xMQTTSocket )
{
   IotMqttPacketInfo_t xIncomingPacket;
   IotMqttError_t xResult = IotMqtt_GetIncomingMQTTPacketTypeAndLength( &xIncomingPacket, getNextByte, ( IotNetworkConnection_t ) xMQTTSocket );
   IotMqtt_Assert( xResult == IOT_MQTT_SUCCESS );
   IotMqtt_Assert( xIncomingPacket.type == MQTT_PACKET_TYPE_PINGRESP );
}