IotMqtt_SerializeConnect

Generate a CONNECT packet from the given parameters.

IotMqttError_t IotMqtt_SerializeConnect( const IotMqttConnectInfo_t * pConnectInfo,
                                         size_t remainingLength,
                                         uint8_t * pBuffer,
                                         size_t bufferSize );

Parameters

[in]	pConnectInfo	User-provided CONNECT information.
[in]	remainingLength	remaining length of the packet to be serialized.
[in,out]	pBuffer	User provided buffer where the CONNECT packet is written.
[in]	bufferSize	Size of the buffer pointed to by pBuffer.

Returns

IOT_MQTT_SUCCESS or IOT_MQTT_NO_MEMORY.

Note

pBuffer must be allocated by caller. Use IotMqtt_GetConnectPacketSize to determine the required size.

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

Example

// Example code below shows how IotMqtt_SerializeConnect() should be used to serialize
// MQTT connect packet and send it to MQTT broker.
// Example uses static memory but dynamically allocated memory can be used as well.
// Get size requirement for the connect packet.

#define mqttexampleSHARED_BUFFER_SIZE 100
static ucSharedBuffer[mqttexampleSHARED_BUFFER_SIZE];
void sendConnectPacket( int xMQTTSocket )
{
   IotMqttConnectInfo_t xConnectInfo;
   size_t xRemainingLength = 0;
   size_t xPacketSize = 0;
   IotMqttError_t xResult;
   size_t xSentBytes = 0;
   // Get size requirement for MQTT connect packet.
   xResult = IotMqtt_GetConnectPacketSize( &xConnectInfo, &xRemainingLength, &xPacketSize );
   IotMqtt_Assert( xResult == IOT_MQTT_SUCCESS );
   // Make sure the packet size is less than static buffer size
   IotMqtt_Assert( xPacketSize < mqttexampleSHARED_BUFFER_SIZE );
   // Serialize MQTT connect packet into provided buffer
   xResult = IotMqtt_SerializeConnect( &xConnectInfo, xRemainingLength, ucSharedBuffer, xPacketSize );
   IotMqtt_Assert( xResult == IOT_MQTT_SUCCESS );
   // xMQTTSocket here is posix socket created and connected to MQTT broker outside of this function.
   xSentBytes = send( xMQTTSocket, ( void * ) ucSharedBuffer, xPacketSize, 0 );
   IotMqtt_Assert( xSentBytes == xPacketSize );
}