Synchronous API implementation. More...

#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include "MQTTClient.h"
#include "MQTTPersistence.h"
#include "utf-8.h"
#include "MQTTProtocol.h"
#include "MQTTProtocolOut.h"
#include "Thread.h"
#include "SocketBuffer.h"
#include "StackTrace.h"
#include "Heap.h"
#include "OsWrapper.h"
#include "VersionInfo.h"
#include "WebSocket.h"
#include "Proxy.h"

Include dependency graph for MQTTClient.c:

Data Structures
struct	qEntry

struct	MQTTClients

struct	props_rc_parms

Macros
#define	URI_SSL "ssl://"

#define	URI_MQTTS "mqtts://"

#define	URI_TCP "tcp://"

#define	URI_MQTT "mqtt://"

#define	URI_WS "ws://"

#define	URI_WSS "wss://"

#define	WINAPI

#define	MAX_INFO_STRINGS 8

Functions
int	MQTTClient_init (void)

void	MQTTClient_global_init (MQTTClient_init_options *inits)
	Global init of mqtt library. More...

static void	MQTTClient_terminate (void)

static void	MQTTClient_emptyMessageQueue (Clients *client)

static int	MQTTClient_deliverMessage (int rc, MQTTClients m, char topicName, int topicLen, MQTTClient_message **message)

static int	clientSockCompare (void a, void b)
	List callback function for comparing clients by socket. More...

static thread_return_type WINAPI	connectionLost_call (void *context)
	Wrapper function to call connection lost on a separate thread. More...

static thread_return_type WINAPI	MQTTClient_run (void *n)

static int	MQTTClient_stop (void)

static void	MQTTClient_closeSession (Clients client, enum MQTTReasonCodes reason, MQTTProperties props)

static int	MQTTClient_cleanSession (Clients *client)

static MQTTResponse	MQTTClient_connectURIVersion (MQTTClient handle, MQTTClient_connectOptions options, const char serverURI, int MQTTVersion, START_TIME_TYPE start, ELAPSED_TIME_TYPE millisecsTimeout, MQTTProperties connectProperties, MQTTProperties willProperties)

static MQTTResponse	MQTTClient_connectURI (MQTTClient handle, MQTTClient_connectOptions options, const char serverURI, MQTTProperties connectProperties, MQTTProperties willProperties)

static int	MQTTClient_disconnect1 (MQTTClient handle, int timeout, int call_connection_lost, int stop, enum MQTTReasonCodes reason, MQTTProperties *props)
	mqttclient_mutex must be locked when you call this function, if multi threaded

static int	MQTTClient_disconnect_internal (MQTTClient handle, int timeout)
	mqttclient_mutex must be locked when you call this function, if multi threaded

static void	MQTTClient_retry (void)

static MQTTPacket *	MQTTClient_cycle (SOCKET sock, ELAPSED_TIME_TYPE timeout, int rc)

static MQTTPacket *	MQTTClient_waitfor (MQTTClient handle, int packet_type, int *rc, int64_t timeout)

static void	MQTTProtocol_checkPendingWrites (void)
	See if any pending writes have been completed, and cleanup if so. More...

static void	MQTTClient_writeComplete (SOCKET socket, int rc)

int	MQTTClient_createWithOptions (MQTTClient handle, const char serverURI, const char clientId, int persistence_type, void persistence_context, MQTTClient_createOptions *options)
	A version of :MQTTClient_create() with additional options. More...

int	MQTTClient_create (MQTTClient handle, const char serverURI, const char clientId, int persistence_type, void persistence_context)
	This function creates an MQTT client ready for connection to the specified server and using the specified persistent storage (see MQTTClient_persistence). More...

void	MQTTClient_destroy (MQTTClient *handle)
	This function frees the memory allocated to an MQTT client (see MQTTClient_create()). More...

void	MQTTClient_freeMessage (MQTTClient_message **message)
	This function frees memory allocated to an MQTT message, including the additional memory allocated to the message payload. More...

void	MQTTClient_free (void *memory)
	This function frees memory allocated by the MQTT C client library, especially the topic name. More...

void	MQTTResponse_free (MQTTResponse response)
	Frees the storage associated with the MQTT response. More...

int	MQTTClient_setDisconnected (MQTTClient handle, void context, MQTTClient_disconnected disconnected)
	Sets the MQTTClient_disconnected() callback function for a client. More...

static thread_return_type WINAPI	call_disconnected (void *context)
	Wrapper function to call disconnected on a separate thread. More...

int	MQTTClient_setPublished (MQTTClient handle, void context, MQTTClient_published published)

int	MQTTClient_setCallbacks (MQTTClient handle, void context, MQTTClient_connectionLost cl, MQTTClient_messageArrived ma, MQTTClient_deliveryComplete dc)
	This function sets the callback functions for a specific client. More...

void	Protocol_processPublication (Publish publish, Clients client, int allocatePayload)

void	setRetryLoopInterval (int keepalive)

MQTTResponse	MQTTClient_connectAll (MQTTClient handle, MQTTClient_connectOptions options, MQTTProperties connectProperties, MQTTProperties *willProperties)

int	MQTTClient_connect (MQTTClient handle, MQTTClient_connectOptions *options)
	This function attempts to connect a previously-created client (see MQTTClient_create()) to an MQTT server using the specified options. More...

MQTTResponse	MQTTClient_connect5 (MQTTClient handle, MQTTClient_connectOptions options, MQTTProperties connectProperties, MQTTProperties *willProperties)
	Attempts to connect a previously-created client (see MQTTClient_create()) to an MQTT server using MQTT version 5.0 and the specified options. More...

void	MQTTProtocol_closeSession (Clients *c, int sendwill)
	mqttclient_mutex must be locked when you call this function, if multi threaded

int	MQTTClient_disconnect (MQTTClient handle, int timeout)
	This function attempts to disconnect the client from the MQTT server. More...

int	MQTTClient_disconnect5 (MQTTClient handle, int timeout, enum MQTTReasonCodes reason, MQTTProperties *props)

int	MQTTClient_isConnected (MQTTClient handle)
	This function allows the client application to test whether or not a client is currently connected to the MQTT server. More...

MQTTResponse	MQTTClient_subscribeMany5 (MQTTClient handle, int count, char const topic, int qos, MQTTSubscribe_options opts, MQTTProperties *props)
	This function attempts to subscribe an MQTT version 5.0 client to a list of topics, which may contain wildcards (see wildcard). More...

int	MQTTClient_subscribeMany (MQTTClient handle, int count, char const topic, int *qos)
	This function attempts to subscribe a client to a list of topics, which may contain wildcards (see wildcard). More...

MQTTResponse	MQTTClient_subscribe5 (MQTTClient handle, const char topic, int qos, MQTTSubscribe_options opts, MQTTProperties *props)
	This function attempts to subscribe an MQTT version 5.0 client to a single topic, which may contain wildcards (see wildcard). More...

int	MQTTClient_subscribe (MQTTClient handle, const char *topic, int qos)
	This function attempts to subscribe a client to a single topic, which may contain wildcards (see wildcard). More...

MQTTResponse	MQTTClient_unsubscribeMany5 (MQTTClient handle, int count, char const topic, MQTTProperties *props)
	This function attempts to remove existing subscriptions to a list of topics made by the specified client using MQTT version 5.0. More...

int	MQTTClient_unsubscribeMany (MQTTClient handle, int count, char const topic)
	This function attempts to remove existing subscriptions to a list of topics made by the specified client. More...

MQTTResponse	MQTTClient_unsubscribe5 (MQTTClient handle, const char topic, MQTTProperties props)
	This function attempts to remove an existing subscription made by the specified client using MQTT 5.0. More...

int	MQTTClient_unsubscribe (MQTTClient handle, const char *topic)
	This function attempts to remove an existing subscription made by the specified client. More...

MQTTResponse	MQTTClient_publish5 (MQTTClient handle, const char topicName, int payloadlen, const void payload, int qos, int retained, MQTTProperties properties, MQTTClient_deliveryToken deliveryToken)
	Attempts to publish a message to a given topic using MQTT version 5.0 (see also MQTTClient_publishMessage5()). More...

int	MQTTClient_publish (MQTTClient handle, const char topicName, int payloadlen, const void payload, int qos, int retained, MQTTClient_deliveryToken *deliveryToken)
	This function attempts to publish a message to a given topic (see also MQTTClient_publishMessage()). More...

MQTTResponse	MQTTClient_publishMessage5 (MQTTClient handle, const char topicName, MQTTClient_message message, MQTTClient_deliveryToken *deliveryToken)
	Attempts to publish a message to the given topic using MQTT version 5.0 (see also MQTTClient_publish5()). More...

int	MQTTClient_publishMessage (MQTTClient handle, const char topicName, MQTTClient_message message, MQTTClient_deliveryToken *deliveryToken)
	This function attempts to publish a message to a given topic (see also MQTTClient_publish()). More...

int	MQTTClient_receive (MQTTClient handle, char *topicName, int topicLen, MQTTClient_message **message, unsigned long timeout)
	This function performs a synchronous receive of incoming messages. More...

void	MQTTClient_yield (void)
	When implementing a single-threaded client, call this function periodically to allow processing of message retries and to send MQTT keepalive pings. More...

int	MQTTClient_waitForCompletion (MQTTClient handle, MQTTClient_deliveryToken mdt, unsigned long timeout)
	This function is called by the client application to synchronize execution of the main thread with completed publication of a message. More...

int	MQTTClient_getPendingDeliveryTokens (MQTTClient handle, MQTTClient_deliveryToken **tokens)
	This function sets a pointer to an array of delivery tokens for messages that are currently in-flight (pending completion). More...

void	MQTTClient_setTraceLevel (enum MQTTCLIENT_TRACE_LEVELS level)
	This function sets the level of trace information which will be returned in the trace callback. More...

void	MQTTClient_setTraceCallback (MQTTClient_traceCallback *callback)
	This function sets the trace callback if needed. More...

int	MQTTClient_setCommandTimeout (MQTTClient handle, unsigned long milliSeconds)
	Sets the timeout value for un/subscribe commands when waiting for the un/suback response from the server. More...

MQTTClient_nameValue *	MQTTClient_getVersionInfo (void)
	This function returns version information about the library. More...

const char *	MQTTClient_strerror (int code)
	Returns a pointer to the string representation of the error or NULL. More...

Variables
const char *	client_timestamp_eye = "MQTTClientV3_Timestamp " BUILD_TIMESTAMP

const char *	client_version_eye = "MQTTClientV3_Version " CLIENT_VERSION

static ClientStates	ClientState

ClientStates *	bstate = &ClientState

MQTTProtocol	state

static pthread_mutex_t	mqttclient_mutex_store = PTHREAD_MUTEX_INITIALIZER

static mutex_type	mqttclient_mutex = &mqttclient_mutex_store

static pthread_mutex_t	socket_mutex_store = PTHREAD_MUTEX_INITIALIZER

static mutex_type	socket_mutex = &socket_mutex_store

static pthread_mutex_t	subscribe_mutex_store = PTHREAD_MUTEX_INITIALIZER

static mutex_type	subscribe_mutex = &subscribe_mutex_store

static pthread_mutex_t	unsubscribe_mutex_store = PTHREAD_MUTEX_INITIALIZER

static mutex_type	unsubscribe_mutex = &unsubscribe_mutex_store

static pthread_mutex_t	connect_mutex_store = PTHREAD_MUTEX_INITIALIZER

static mutex_type	connect_mutex = &connect_mutex_store

static volatile int	library_initialized = 0

static List *	handles = NULL

static int	running = 0

static int	tostop = 0

static thread_id_type	run_id = 0

static int	retryLoopIntervalms = 5000

Detailed Description

Synchronous API implementation.

Function Documentation

◆ call_disconnected()

static thread_return_type WINAPI call_disconnected ( void * context )

static

Wrapper function to call disconnected on a separate thread.

A separate thread is needed to allow the disconnected function to make API calls (e.g. connect)

Parameters

context a pointer to the relevant client

Returns: thread_return_type standard thread return value - not used here

◆ clientSockCompare()

static int clientSockCompare	(	void *	a,
		void *	b
	)

static

List callback function for comparing clients by socket.

Parameters

a	first integer value
b	second integer value

Returns: boolean indicating whether a and b are equal

◆ connectionLost_call()

static thread_return_type WINAPI connectionLost_call ( void * context )

static

Wrapper function to call connection lost on a separate thread.

A separate thread is needed to allow the connectionLost function to make API calls (e.g. connect)

Parameters

context a pointer to the relevant client

Returns: thread_return_type standard thread return value - not used here

◆ MQTTClient_connect()

int MQTTClient_connect	(	MQTTClient	handle,
		MQTTClient_connectOptions *	options
	)

This function attempts to connect a previously-created client (see MQTTClient_create()) to an MQTT server using the specified options.

If you want to enable asynchronous message and status notifications, you must call MQTTClient_setCallbacks() prior to MQTTClient_connect().

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
options	A pointer to a valid MQTTClient_connectOptions structure.

Returns: ::MQTTCLIENT_SUCCESS if the client successfully connects to the server. An error code is returned if the client was unable to connect to the server. Error codes greater than 0 are returned by the MQTT protocol:

1: Connection refused: Unacceptable protocol version
2: Connection refused: Identifier rejected
3: Connection refused: Server unavailable
4: Connection refused: Bad user name or password
5: Connection refused: Not authorized
6-255: Reserved for future use

◆ MQTTClient_connect5()

MQTTResponse MQTTClient_connect5	(	MQTTClient	handle,
		MQTTClient_connectOptions *	options,
		MQTTProperties *	connectProperties,
		MQTTProperties *	willProperties
	)

Attempts to connect a previously-created client (see MQTTClient_create()) to an MQTT server using MQTT version 5.0 and the specified options.

If you want to enable asynchronous message and status notifications, you must call MQTTClient_setCallbacks() prior to MQTTClient_connect().

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
options	A pointer to a valid MQTTClient_connectOptions structure.
connectProperties	the MQTT 5.0 connect properties to use
willProperties	the MQTT 5.0 properties to set on the will message

Returns: the MQTT 5.0 response information: error codes and properties.

◆ MQTTClient_create()

int MQTTClient_create	(	MQTTClient *	handle,
		const char *	serverURI,
		const char *	clientId,
		int	persistence_type,
		void *	persistence_context
	)

This function creates an MQTT client ready for connection to the specified server and using the specified persistent storage (see MQTTClient_persistence).

◆ MQTTClient_createWithOptions()

int MQTTClient_createWithOptions	(	MQTTClient *	handle,
		const char *	serverURI,
		const char *	clientId,
		int	persistence_type,
		void *	persistence_context,
		MQTTClient_createOptions *	options
	)

A version of :MQTTClient_create() with additional options.

This function creates an MQTT client ready for connection to the specified server and using the specified persistent storage (see MQTTClient_persistence). See also MQTTClient_destroy().

Parameters

handle	A pointer to an ::MQTTClient handle. The handle is populated with a valid client reference following a successful return from this function.
serverURI	A null-terminated string specifying the server to which the client will connect. It takes the form protocol://host:port. Currently, protocol must be tcp or ssl. For host, you can specify either an IP address or a host name. For instance, to connect to a server running on the local machines with the default MQTT port, specify tcp://localhost:1883.
clientId	The client identifier passed to the server when the client connects to it. It is a null-terminated UTF-8 encoded string.
persistence_type	The type of persistence to be used by the client: MQTTCLIENT_PERSISTENCE_NONE: Use in-memory persistence. If the device or system on which the client is running fails or is switched off, the current state of any in-flight messages is lost and some messages may not be delivered even at QoS1 and QoS2. MQTTCLIENT_PERSISTENCE_DEFAULT: Use the default (file system-based) persistence mechanism. Status about in-flight messages is held in persistent storage and provides some protection against message loss in the case of unexpected failure. MQTTCLIENT_PERSISTENCE_USER: Use an application-specific persistence implementation. Using this type of persistence gives control of the persistence mechanism to the application. The application has to implement the MQTTClient_persistence interface.
persistence_context	If the application uses MQTTCLIENT_PERSISTENCE_NONE persistence, this argument is unused and should be set to NULL. For MQTTCLIENT_PERSISTENCE_DEFAULT persistence, it should be set to the location of the persistence directory (if set to NULL, the persistence directory used is the working directory). Applications that use MQTTCLIENT_PERSISTENCE_USER persistence set this argument to point to a valid MQTTClient_persistence structure.
options	additional options for the create.

Returns: ::MQTTCLIENT_SUCCESS if the client is successfully created, otherwise an error code is returned.

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◆ MQTTClient_destroy()

void MQTTClient_destroy ( MQTTClient * handle )

This function frees the memory allocated to an MQTT client (see MQTTClient_create()).

It should be called when the client is no longer required.

Parameters

handle A pointer to the handle referring to the ::MQTTClient structure to be freed.

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◆ MQTTClient_disconnect()

int MQTTClient_disconnect	(	MQTTClient	handle,
		int	timeout
	)

This function attempts to disconnect the client from the MQTT server.

In order to allow the client time to complete handling of messages that are in-flight when this function is called, a timeout period is specified. When the timeout period has expired, the client disconnects even if there are still outstanding message acknowledgements. The next time the client connects to the same server, any QoS 1 or 2 messages which have not completed will be retried depending on the cleansession settings for both the previous and the new connection (see MQTTClient_connectOptions.cleansession and MQTTClient_connect()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
timeout	The client delays disconnection for up to this time (in milliseconds) in order to allow in-flight message transfers to complete.

Returns: ::MQTTCLIENT_SUCCESS if the client successfully disconnects from the server. An error code is returned if the client was unable to disconnect from the server

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◆ MQTTClient_free()

void MQTTClient_free ( void * ptr )

This function frees memory allocated by the MQTT C client library, especially the topic name.

This is needed on Windows when the client libary and application program have been compiled with different versions of the C compiler. It is thus good policy to always use this function when freeing any MQTT C client- allocated memory.

Parameters

ptr	The pointer to the client library storage to be freed.

◆ MQTTClient_freeMessage()

void MQTTClient_freeMessage ( MQTTClient_message ** msg )

This function frees memory allocated to an MQTT message, including the additional memory allocated to the message payload.

The client application calls this function when the message has been fully processed. Important note: This function does not free the memory allocated to a message topic string. It is the responsibility of the client application to free this memory using the MQTTClient_free() library function.

Parameters

msg	The address of a pointer to the MQTTClient_message structure to be freed.

◆ MQTTClient_getPendingDeliveryTokens()

int MQTTClient_getPendingDeliveryTokens	(	MQTTClient	handle,
		MQTTClient_deliveryToken **	tokens
	)

This function sets a pointer to an array of delivery tokens for messages that are currently in-flight (pending completion).

Important note: The memory used to hold the array of tokens is malloc()'d in this function. The client application is responsible for freeing this memory when it is no longer required.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
tokens	The address of a pointer to an ::MQTTClient_deliveryToken. When the function returns successfully, the pointer is set to point to an array of tokens representing messages pending completion. The last member of the array is set to -1 to indicate there are no more tokens. If no tokens are pending, the pointer is set to NULL.

Returns: ::MQTTCLIENT_SUCCESS if the function returns successfully. An error code is returned if there was a problem obtaining the list of pending tokens.

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◆ MQTTClient_getVersionInfo()

MQTTClient_nameValue* MQTTClient_getVersionInfo ( void )

This function returns version information about the library.

no trace information will be returned.

Returns: an array of strings describing the library. The last entry is a NULL pointer.

◆ MQTTClient_global_init()

void MQTTClient_global_init ( MQTTClient_init_options * inits )

Global init of mqtt library.

Call once on program start to set global behaviour. do_openssl_init - if mqtt library should initialize OpenSSL (1) or rely on the caller to do it before using the library (0)

◆ MQTTClient_isConnected()

int MQTTClient_isConnected ( MQTTClient handle )

This function allows the client application to test whether or not a client is currently connected to the MQTT server.

Parameters

handle A valid client handle from a successful call to MQTTClient_create().

Returns: Boolean true if the client is connected, otherwise false.

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◆ MQTTClient_publish()

int MQTTClient_publish	(	MQTTClient	handle,
		const char *	topicName,
		int	payloadlen,
		const void *	payload,
		int	qos,
		int	retained,
		MQTTClient_deliveryToken *	dt
	)

This function attempts to publish a message to a given topic (see also MQTTClient_publishMessage()).

An ::MQTTClient_deliveryToken is issued when this function returns successfully. If the client application needs to test for succesful delivery of QoS1 and QoS2 messages, this can be done either asynchronously or synchronously (see async, MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topicName	The topic associated with this message.
payloadlen	The length of the payload in bytes.
payload	A pointer to the byte array payload of the message.
qos	The qos of the message.
retained	The retained flag for the message.
dt	A pointer to an ::MQTTClient_deliveryToken. This is populated with a token representing the message when the function returns successfully. If your application does not use delivery tokens, set this argument to NULL.

Returns: ::MQTTCLIENT_SUCCESS if the message is accepted for publication. An error code is returned if there was a problem accepting the message.

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◆ MQTTClient_publish5()

MQTTResponse MQTTClient_publish5	(	MQTTClient	handle,
		const char *	topicName,
		int	payloadlen,
		const void *	payload,
		int	qos,
		int	retained,
		MQTTProperties *	properties,
		MQTTClient_deliveryToken *	dt
	)

Attempts to publish a message to a given topic using MQTT version 5.0 (see also MQTTClient_publishMessage5()).

An ::MQTTClient_deliveryToken is issued when this function returns successfully. If the client application needs to test for succesful delivery of QoS1 and QoS2 messages, this can be done either asynchronously or synchronously (see async, MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topicName	The topic associated with this message.
payloadlen	The length of the payload in bytes.
payload	A pointer to the byte array payload of the message.
qos	The qos of the message.
retained	The retained flag for the message.
properties	the MQTT 5.0 properties to be used
dt	A pointer to an ::MQTTClient_deliveryToken. This is populated with a token representing the message when the function returns successfully. If your application does not use delivery tokens, set this argument to NULL.

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_publishMessage()

int MQTTClient_publishMessage	(	MQTTClient	handle,
		const char *	topicName,
		MQTTClient_message *	msg,
		MQTTClient_deliveryToken *	dt
	)

This function attempts to publish a message to a given topic (see also MQTTClient_publish()).

An ::MQTTClient_deliveryToken is issued when this function returns successfully. If the client application needs to test for succesful delivery of QoS1 and QoS2 messages, this can be done either asynchronously or synchronously (see async, MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topicName	The topic associated with this message.
msg	A pointer to a valid MQTTClient_message structure containing the payload and attributes of the message to be published.
dt	A pointer to an ::MQTTClient_deliveryToken. This is populated with a token representing the message when the function returns successfully. If your application does not use delivery tokens, set this argument to NULL.

Returns: ::MQTTCLIENT_SUCCESS if the message is accepted for publication. An error code is returned if there was a problem accepting the message.

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◆ MQTTClient_publishMessage5()

MQTTResponse MQTTClient_publishMessage5	(	MQTTClient	handle,
		const char *	topicName,
		MQTTClient_message *	msg,
		MQTTClient_deliveryToken *	dt
	)

Attempts to publish a message to the given topic using MQTT version 5.0 (see also MQTTClient_publish5()).

An ::MQTTClient_deliveryToken is issued when this function returns successfully. If the client application needs to test for succesful delivery of QoS1 and QoS2 messages, this can be done either asynchronously or synchronously (see async, MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topicName	The topic associated with this message.
msg	A pointer to a valid MQTTClient_message structure containing the payload and attributes of the message to be published.
dt	A pointer to an ::MQTTClient_deliveryToken. This is populated with a token representing the message when the function returns successfully. If your application does not use delivery tokens, set this argument to NULL.

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_receive()

int MQTTClient_receive	(	MQTTClient	handle,
		char **	topicName,
		int *	topicLen,
		MQTTClient_message **	message,
		unsigned long	timeout
	)

This function performs a synchronous receive of incoming messages.

It should be used only when the client application has not set callback methods to support asynchronous receipt of messages (see async and MQTTClient_setCallbacks()). Using this function allows a single-threaded client subscriber application to be written. When called, this function blocks until the next message arrives or the specified timeout expires (see also MQTTClient_yield()).

Important note: The application must free() the memory allocated to the topic and the message when processing is complete (see MQTTClient_freeMessage()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topicName	The address of a pointer to a topic. This function allocates the memory for the topic and returns it to the application by setting topicName to point to the topic.
topicLen	The length of the topic. If the return code from this function is ::MQTTCLIENT_TOPICNAME_TRUNCATED, the topic contains embedded NULL characters and the full topic should be retrieved by using topicLen.
message	The address of a pointer to the received message. This function allocates the memory for the message and returns it to the application by setting message to point to the received message. The pointer is set to NULL if the timeout expires.
timeout	The length of time to wait for a message in milliseconds.

Returns: ::MQTTCLIENT_SUCCESS or ::MQTTCLIENT_TOPICNAME_TRUNCATED if a message is received. ::MQTTCLIENT_SUCCESS can also indicate that the timeout expired, in which case message is NULL. An error code is returned if there was a problem trying to receive a message.

◆ MQTTClient_setCallbacks()

int MQTTClient_setCallbacks	(	MQTTClient	handle,
		void *	context,
		MQTTClient_connectionLost *	cl,
		MQTTClient_messageArrived *	ma,
		MQTTClient_deliveryComplete *	dc
	)

This function sets the callback functions for a specific client.

If your client application doesn't use a particular callback, set the relevant parameter to NULL. Calling MQTTClient_setCallbacks() puts the client into multi-threaded mode. Any necessary message acknowledgements and status communications are handled in the background without any intervention from the client application. See async for more information.

Note: The MQTT client must be disconnected when this function is called.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
context	A pointer to any application-specific context. The the context pointer is passed to each of the callback functions to provide access to the context information in the callback.
cl	A pointer to an MQTTClient_connectionLost() callback function. You can set this to NULL if your application doesn't handle disconnections.
ma	A pointer to an MQTTClient_messageArrived() callback function. This callback function must be set when you call MQTTClient_setCallbacks(), as otherwise there would be nowhere to deliver any incoming messages.
dc	A pointer to an MQTTClient_deliveryComplete() callback function. You can set this to NULL if your application publishes synchronously or if you do not want to check for successful delivery.

Returns: ::MQTTCLIENT_SUCCESS if the callbacks were correctly set, ::MQTTCLIENT_FAILURE if an error occurred.

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◆ MQTTClient_setCommandTimeout()

int MQTTClient_setCommandTimeout	(	MQTTClient	handle,
		unsigned long	milliSeconds
	)

Sets the timeout value for un/subscribe commands when waiting for the un/suback response from the server.

Values less than 5000 are not allowed.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
milliSeconds	the maximum number of milliseconds to wait

Returns: MQTTCLIENT_SUCCESS or MQTTCLIENT_FAILURE

◆ MQTTClient_setDisconnected()

int MQTTClient_setDisconnected	(	MQTTClient	handle,
		void *	context,
		MQTTClient_disconnected *	co
	)

Sets the MQTTClient_disconnected() callback function for a client.

This will be called if a disconnect packet is received from the server. Only valid for MQTT V5 and above.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
context	A pointer to any application-specific context. The the context pointer is passed to each of the callback functions to provide access to the context information in the callback.
co	A pointer to an MQTTClient_disconnected() callback function. NULL removes the callback setting.

Returns: ::MQTTCLIENT_SUCCESS if the callbacks were correctly set, ::MQTTCLIENT_FAILURE if an error occurred.

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◆ MQTTClient_setTraceCallback()

void MQTTClient_setTraceCallback ( MQTTClient_traceCallback * callback )

This function sets the trace callback if needed.

If set to NULL, no trace information will be returned. The default trace level is MQTTASYNC_TRACE_MINIMUM.

Parameters

callback a pointer to the function which will handle the trace information

◆ MQTTClient_setTraceLevel()

void MQTTClient_setTraceLevel ( enum MQTTCLIENT_TRACE_LEVELS level )

This function sets the level of trace information which will be returned in the trace callback.

Parameters

level the trace level required

◆ MQTTClient_strerror()

const char* MQTTClient_strerror ( int code )

Returns a pointer to the string representation of the error or NULL.

Do not free after use. Returns NULL if the error code is unknown.

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◆ MQTTClient_subscribe()

int MQTTClient_subscribe	(	MQTTClient	handle,
		const char *	topic,
		int	qos
	)

This function attempts to subscribe a client to a single topic, which may contain wildcards (see wildcard).

This call also specifies the qos requested for the subscription (see also MQTTClient_subscribeMany()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topic	The subscription topic, which may include wildcards.
qos	The requested quality of service for the subscription.

Returns: ::MQTTCLIENT_SUCCESS if the subscription request is successful. An error code is returned if there was a problem registering the subscription.

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◆ MQTTClient_subscribe5()

MQTTResponse MQTTClient_subscribe5	(	MQTTClient	handle,
		const char *	topic,
		int	qos,
		MQTTSubscribe_options *	opts,
		MQTTProperties *	props
	)

This function attempts to subscribe an MQTT version 5.0 client to a single topic, which may contain wildcards (see wildcard).

This call also specifies the qos requested for the subscription (see also MQTTClient_subscribeMany()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topic	The subscription topic, which may include wildcards.
qos	The requested quality of service for the subscription.
opts	the MQTT 5.0 subscribe options to be used
props	the MQTT 5.0 properties to be used

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_subscribeMany()

int MQTTClient_subscribeMany	(	MQTTClient	handle,
		int	count,
		char const	topic,
		int *	qos
	)

This function attempts to subscribe a client to a list of topics, which may contain wildcards (see wildcard).

This call also specifies the qos requested for each topic (see also MQTTClient_subscribe()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
count	The number of topics for which the client is requesting subscriptions.
topic	An array (of length count) of pointers to topics, each of which may include wildcards.
qos	An array (of length count) of qos values. qos[n] is the requested QoS for topic[n].

Returns: ::MQTTCLIENT_SUCCESS if the subscription request is successful. An error code is returned if there was a problem registering the subscriptions.

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◆ MQTTClient_subscribeMany5()

MQTTResponse MQTTClient_subscribeMany5	(	MQTTClient	handle,
		int	count,
		char const	topic,
		int *	qos,
		MQTTSubscribe_options *	opts,
		MQTTProperties *	props
	)

This function attempts to subscribe an MQTT version 5.0 client to a list of topics, which may contain wildcards (see wildcard).

This call also specifies the qos requested for each topic (see also MQTTClient_subscribe()).

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
count	The number of topics for which the client is requesting subscriptions.
topic	An array (of length count) of pointers to topics, each of which may include wildcards.
qos	An array (of length count) of qos values. qos[n] is the requested QoS for topic[n].
opts	the MQTT 5.0 subscribe options to be used
props	the MQTT 5.0 properties to be used

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_unsubscribe()

int MQTTClient_unsubscribe	(	MQTTClient	handle,
		const char *	topic
	)

This function attempts to remove an existing subscription made by the specified client.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topic	The topic for the subscription to be removed, which may include wildcards (see wildcard).

Returns: ::MQTTCLIENT_SUCCESS if the subscription is removed. An error code is returned if there was a problem removing the subscription.

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◆ MQTTClient_unsubscribe5()

MQTTResponse MQTTClient_unsubscribe5	(	MQTTClient	handle,
		const char *	topic,
		MQTTProperties *	props
	)

This function attempts to remove an existing subscription made by the specified client using MQTT 5.0.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
topic	The topic for the subscription to be removed, which may include wildcards (see wildcard).
props	the MQTT 5.0 properties to be used

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_unsubscribeMany()

int MQTTClient_unsubscribeMany	(	MQTTClient	handle,
		int	count,
		char const	topic
	)

This function attempts to remove existing subscriptions to a list of topics made by the specified client.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
count	The number subscriptions to be removed.
topic	An array (of length count) of pointers to the topics of the subscriptions to be removed, each of which may include wildcards.

Returns: ::MQTTCLIENT_SUCCESS if the subscriptions are removed. An error code is returned if there was a problem removing the subscriptions.

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◆ MQTTClient_unsubscribeMany5()

MQTTResponse MQTTClient_unsubscribeMany5	(	MQTTClient	handle,
		int	count,
		char const	topic,
		MQTTProperties *	props
	)

This function attempts to remove existing subscriptions to a list of topics made by the specified client using MQTT version 5.0.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
count	The number subscriptions to be removed.
topic	An array (of length count) of pointers to the topics of the subscriptions to be removed, each of which may include wildcards.
props	the MQTT 5.0 properties to be used

Returns: the MQTT 5.0 response information: error codes and properties.

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◆ MQTTClient_waitForCompletion()

int MQTTClient_waitForCompletion	(	MQTTClient	handle,
		MQTTClient_deliveryToken	dt,
		unsigned long	timeout
	)

This function is called by the client application to synchronize execution of the main thread with completed publication of a message.

When called, MQTTClient_waitForCompletion() blocks execution until the message has been successful delivered or the specified timeout has expired. See async.

Parameters

handle	A valid client handle from a successful call to MQTTClient_create().
dt	The ::MQTTClient_deliveryToken that represents the message being tested for successful delivery. Delivery tokens are issued by the publishing functions MQTTClient_publish() and MQTTClient_publishMessage().
timeout	The maximum time to wait in milliseconds.

Returns: ::MQTTCLIENT_SUCCESS if the message was successfully delivered. An error code is returned if the timeout expires or there was a problem checking the token.

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◆ MQTTClient_yield()

void MQTTClient_yield ( void )

When implementing a single-threaded client, call this function periodically to allow processing of message retries and to send MQTT keepalive pings.

If the application is calling MQTTClient_receive() regularly, then it is not necessary to call this function.

◆ MQTTProtocol_checkPendingWrites()

static void MQTTProtocol_checkPendingWrites ( void )

static

See if any pending writes have been completed, and cleanup if so.

Cleaning up means removing any publication data that was stored because the write did not originally complete.

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◆ MQTTResponse_free()

void MQTTResponse_free ( MQTTResponse response )

Frees the storage associated with the MQTT response.

Parameters

response the response structure to be freed

Variable Documentation

◆ ClientState

ClientStates ClientState

static

Initial value:

=
{
        CLIENT_VERSION, 
        NULL 
}

Data Structures

Macros

Functions

Variables

Detailed Description

Function Documentation

◆ call_disconnected()

◆ clientSockCompare()

◆ connectionLost_call()

◆ MQTTClient_connect()

◆ MQTTClient_connect5()

◆ MQTTClient_create()

◆ MQTTClient_createWithOptions()

◆ MQTTClient_destroy()

◆ MQTTClient_disconnect()

◆ MQTTClient_free()

◆ MQTTClient_freeMessage()

◆ MQTTClient_getPendingDeliveryTokens()

◆ MQTTClient_getVersionInfo()

◆ MQTTClient_global_init()

◆ MQTTClient_isConnected()

◆ MQTTClient_publish()

◆ MQTTClient_publish5()

◆ MQTTClient_publishMessage()

◆ MQTTClient_publishMessage5()

◆ MQTTClient_receive()

◆ MQTTClient_setCallbacks()

◆ MQTTClient_setCommandTimeout()

◆ MQTTClient_setDisconnected()

◆ MQTTClient_setTraceCallback()

◆ MQTTClient_setTraceLevel()

◆ MQTTClient_strerror()

◆ MQTTClient_subscribe()

◆ MQTTClient_subscribe5()

◆ MQTTClient_subscribeMany()

◆ MQTTClient_subscribeMany5()

◆ MQTTClient_unsubscribe()

◆ MQTTClient_unsubscribe5()

◆ MQTTClient_unsubscribeMany()

◆ MQTTClient_unsubscribeMany5()

◆ MQTTClient_waitForCompletion()

◆ MQTTClient_yield()

◆ MQTTProtocol_checkPendingWrites()

◆ MQTTResponse_free()

Variable Documentation

◆ ClientState