MQTTAgent_Init

Perform any initialization the MQTT agent requires before it can be used. Must be called before any other function.

MQTTStatus_t MQTTAgent_Init( MQTTAgentContext_t * pMqttAgentContext,
                             const MQTTAgentMessageInterface_t * pMsgInterface,
                             const MQTTFixedBuffer_t * pNetworkBuffer,
                             const TransportInterface_t * pTransportInterface,
                             MQTTGetCurrentTimeFunc_t getCurrentTimeMs,
                             MQTTAgentIncomingPublishCallback_t incomingCallback,
                             void * pIncomingPacketContext );

Parameters

[in]	pMqttAgentContext	Pointer to struct to initialize.
[in]	pMsgInterface	Command interface to use for allocating and sending commands.
[in]	pNetworkBuffer	Pointer to network buffer to use.
[in]	pTransportInterface	Transport interface to use with the MQTT library. See https://www.freertos.org/network-interface.html
[in]	getCurrentTimeMs	Pointer to a function that returns a count value that increments every millisecond.
[in]	incomingCallback	The callback to execute when receiving publishes.
[in]	pIncomingPacketContext	A pointer to a context structure defined by the application writer.

Note

The pIncomingPacketContext context provided for the incoming publish callback MUST remain in scope throughout the period that the agent task is running.

Returns

Appropriate status code from MQTT_Init().

Example

// Function for obtaining a timestamp.
uint32_t getTimeStampMs();
// Callback function for receiving packets.
void incomingPublishCallback( MQTTAgentContext_t * pMqttAgentContext,
                              uint16_t packetId,
                              MQTTPublishInfo_t * pPublishInfo );
// Platform function for network send interface.
int32_t networkSend( NetworkContext_t * pContext, const void * pBuffer, size_t bytes );
// Platform for network receive interface.
int32_t networkRecv( NetworkContext_t * pContext, void * pBuffer, size_t bytes );
 
// Platform function for Agent Message Send.
bool agentSendMessage( MQTTAgentMessageContext_t * pMsgCtx,
                       MQTTAgentCommand_t * const * pCommandToSend,
                       uint32_t blockTimeMs );
// Platform function for Agent Message Receive.
bool agentReceiveMessage( MQTTAgentMessageContext_t * pMsgCtx,
                          MQTTAgentCommand_t ** pCommandToSend,
                          uint32_t blockTimeMs );
// Platform function to Get Agent Command.
MQTTAgentCommand_t * getCommand( uint32_t blockTimeMs );
// Platform function to Release Agent Command.
bool releaseCommand( MQTTAgentCommand_t * pCommandToRelease );
 
// Variables used in this example.
MQTTAgentMessageInterface_t messageInterface;
MQTTAgentMessageContext_t messageContext;
MQTTAgentContext_t agentContext;
TransportInterface_t transport;
// Buffer for storing outgoing and incoming MQTT packets.
MQTTFixedBuffer_t fixedBuffer;
uint8_t buffer[ 1024 ];
MQTTStatus_t status;
 
// Set transport interface members.
transport.pNetworkContext = &someTransportContext;
transport.send = networkSend;
transport.recv = networkRecv;
 
// Set agent message interface members.
messageInterface.pMsgCtx = &messageContext;
messageInterface.send = agentSendMessage;
messageInterface.recv = agentReceiveMessage;
messageInterface.getCommand = getCommand;
messageInterface.releaseCommand = releaseCommand;
 
// Set buffer members.
fixedBuffer.pBuffer = buffer;
fixedBuffer.size = 1024;
 
status = MQTTAgent_Init( &agentContext,
                         &messageInterface,
                         &networkBuffer,
                         &transportInterface,
                         stubGetTime,
                         stubPublishCallback,
                         incomingPacketContext );
 
if( status == MQTTSuccess )
{
   // Do something with agentContext. The transport and message interfaces, and
   // fixedBuffer structs were copied into the context, so the original structs
   // do not need to stay in scope.
}