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mqttClient/include/paho-mqtt/MQTTClient.h
mreenen 9e2a88bb5f convert to mqtt clock
2023-01-26 23:33:16 +01:00

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/*******************************************************************************
* Copyright (c) 2009, 2022 IBM Corp., Ian Craggs and others
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* https://www.eclipse.org/legal/epl-2.0/
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Ian Craggs - initial API and implementation and/or initial documentation
* Ian Craggs, Allan Stockdill-Mander - SSL updates
* Ian Craggs - multiple server connection support
* Ian Craggs - MQTT 3.1.1 support
* Ian Craggs - remove const from eyecatchers #168
*******************************************************************************/
/**
* @cond MQTTClient_internal
* @mainpage MQTT Client Library Internals
* In the beginning there was one MQTT C client library, MQTTClient, as implemented in MQTTClient.c
* This library was designed to be easy to use for applications which didn't mind if some of the calls
* blocked for a while. For instance, the MQTTClient_connect call will block until a successful
* connection has completed, or a connection has failed, which could be as long as the "connection
* timeout" interval, whose default is 30 seconds.
*
* However in mobile devices and other windowing environments, blocking on the GUI thread is a bad
* thing as it causes the user interface to freeze. Hence a new API, MQTTAsync, implemented
* in MQTTAsync.c, was devised. There are no blocking calls in this library, so it is well suited
* to GUI and mobile environments, at the expense of some extra complexity.
*
* Both libraries are designed to be sparing in the use of threads. So multiple client objects are
* handled by one or two threads, with a select call in Socket_getReadySocket(), used to determine
* when a socket has incoming data. This API is thread safe: functions may be called by multiple application
* threads, with the exception of ::MQTTClient_yield and ::MQTTClient_receive, which are intended
* for single threaded environments only.
*
* @endcond
* @cond MQTTClient_main
* @mainpage MQTT Client library for C (MQTTClient)
* © Copyright 2009, 2022 IBM Corp., Ian Craggs and others
*
* @brief An MQTT client library in C.
*
* These pages describe the original more synchronous API which might be
* considered easier to use. Some of the calls will block. For the new
* totally asynchronous API where no calls block, which is especially suitable
* for use in windowed environments, see the
* <a href="../../MQTTAsync/html/index.html">MQTT C Client Asynchronous API Documentation</a>.
* The MQTTClient API is not thread safe, whereas the MQTTAsync API is.
*
* An MQTT client application connects to MQTT-capable servers.
* A typical client is responsible for collecting information from a telemetry
* device and publishing the information to the server. It can also subscribe
* to topics, receive messages, and use this information to control the
* telemetry device.
*
* MQTT clients implement the published MQTT v3 protocol. You can write your own
* API to the MQTT protocol using the programming language and platform of your
* choice. This can be time-consuming and error-prone.
*
* To simplify writing MQTT client applications, this library encapsulates
* the MQTT v3 protocol for you. Using this library enables a fully functional
* MQTT client application to be written in a few lines of code.
* The information presented here documents the API provided
* by the MQTT Client library for C.
*
* <b>Using the client</b><br>
* Applications that use the client library typically use a similar structure:
* <ul>
* <li>Create a client object</li>
* <li>Set the options to connect to an MQTT server</li>
* <li>Set up callback functions if multi-threaded (asynchronous mode)
* operation is being used (see @ref async).</li>
* <li>Subscribe to any topics the client needs to receive</li>
* <li>Repeat until finished:</li>
* <ul>
* <li>Publish any messages the client needs to</li>
* <li>Handle any incoming messages</li>
* </ul>
* <li>Disconnect the client</li>
* <li>Free any memory being used by the client</li>
* </ul>
* Some simple examples are shown here:
* <ul>
* <li>@ref pubsync</li>
* <li>@ref pubasync</li>
* <li>@ref subasync</li>
* </ul>
* Additional information about important concepts is provided here:
* <ul>
* <li>@ref async</li>
* <li>@ref callbacks</li>
* <li>@ref wildcard</li>
* <li>@ref qos</li>
* <li>@ref tracing</li>
* </ul>
* @endcond
*/
/*
/// @cond EXCLUDE
*/
#if !defined(MQTTCLIENT_H)
#define MQTTCLIENT_H
#if defined(__cplusplus)
extern "C" {
#endif
#include <stdio.h>
/*
/// @endcond
*/
#include "MQTTExportDeclarations.h"
#include "MQTTProperties.h"
#include "MQTTReasonCodes.h"
#include "MQTTSubscribeOpts.h"
#if !defined(NO_PERSISTENCE)
#include "MQTTClientPersistence.h"
#endif
/**
* Return code: No error. Indicates successful completion of an MQTT client
* operation.
*/
#define MQTTCLIENT_SUCCESS 0
/**
* Return code: A generic error code indicating the failure of an MQTT client
* operation.
*/
#define MQTTCLIENT_FAILURE -1
/* error code -2 is MQTTCLIENT_PERSISTENCE_ERROR */
/**
* Return code: The client is disconnected.
*/
#define MQTTCLIENT_DISCONNECTED -3
/**
* Return code: The maximum number of messages allowed to be simultaneously
* in-flight has been reached.
*/
#define MQTTCLIENT_MAX_MESSAGES_INFLIGHT -4
/**
* Return code: An invalid UTF-8 string has been detected.
*/
#define MQTTCLIENT_BAD_UTF8_STRING -5
/**
* Return code: A NULL parameter has been supplied when this is invalid.
*/
#define MQTTCLIENT_NULL_PARAMETER -6
/**
* Return code: The topic has been truncated (the topic string includes
* embedded NULL characters). String functions will not access the full topic.
* Use the topic length value to access the full topic.
*/
#define MQTTCLIENT_TOPICNAME_TRUNCATED -7
/**
* Return code: A structure parameter does not have the correct eyecatcher
* and version number.
*/
#define MQTTCLIENT_BAD_STRUCTURE -8
/**
* Return code: A QoS value that falls outside of the acceptable range (0,1,2)
*/
#define MQTTCLIENT_BAD_QOS -9
/**
* Return code: Attempting SSL connection using non-SSL version of library
*/
#define MQTTCLIENT_SSL_NOT_SUPPORTED -10
/**
* Return code: unrecognized MQTT version
*/
#define MQTTCLIENT_BAD_MQTT_VERSION -11
/**
* Return code: protocol prefix in serverURI should be:
* @li @em tcp:// or @em mqtt:// - Insecure TCP
* @li @em ssl:// or @em mqtts:// - Encrypted SSL/TLS
* @li @em ws:// - Insecure websockets
* @li @em wss:// - Secure web sockets
* The TLS enabled prefixes (ssl, mqtts, wss) are only valid if a TLS
* version of the library is linked with.
*/
#define MQTTCLIENT_BAD_PROTOCOL -14
/**
* Return code: option not applicable to the requested version of MQTT
*/
#define MQTTCLIENT_BAD_MQTT_OPTION -15
/**
* Return code: call not applicable to the requested version of MQTT
*/
#define MQTTCLIENT_WRONG_MQTT_VERSION -16
/**
* Return code: 0 length will topic on connect
*/
#define MQTTCLIENT_0_LEN_WILL_TOPIC -17
/**
* Default MQTT version to connect with. Use 3.1.1 then fall back to 3.1
*/
#define MQTTVERSION_DEFAULT 0
/**
* MQTT version to connect with: 3.1
*/
#define MQTTVERSION_3_1 3
/**
* MQTT version to connect with: 3.1.1
*/
#define MQTTVERSION_3_1_1 4
/**
* MQTT version to connect with: 5
*/
#define MQTTVERSION_5 5
/**
* Bad return code from subscribe, as defined in the 3.1.1 specification
*/
#define MQTT_BAD_SUBSCRIBE 0x80
/**
* Initialization options
*/
typedef struct
{
/** The eyecatcher for this structure. Must be MQTG. */
char struct_id[4];
/** The version number of this structure. Must be 0 */
int struct_version;
/** 1 = we do openssl init, 0 = leave it to the application */
int do_openssl_init;
} MQTTClient_init_options;
#define MQTTClient_init_options_initializer { {'M', 'Q', 'T', 'G'}, 0, 0 }
/**
* 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)
*/
LIBMQTT_API void MQTTClient_global_init(MQTTClient_init_options* inits);
/**
* A handle representing an MQTT client. A valid client handle is available
* following a successful call to MQTTClient_create().
*/
typedef void* MQTTClient;
/**
* A value representing an MQTT message. A delivery token is returned to the
* client application when a message is published. The token can then be used to
* check that the message was successfully delivered to its destination (see
* MQTTClient_publish(),
* MQTTClient_publishMessage(),
* MQTTClient_deliveryComplete(),
* MQTTClient_waitForCompletion() and
* MQTTClient_getPendingDeliveryTokens()).
*/
typedef int MQTTClient_deliveryToken;
typedef int MQTTClient_token;
/**
* A structure representing the payload and attributes of an MQTT message. The
* message topic is not part of this structure (see MQTTClient_publishMessage(),
* MQTTClient_publish(), MQTTClient_receive(), MQTTClient_freeMessage()
* and MQTTClient_messageArrived()).
*/
typedef struct
{
/** The eyecatcher for this structure. must be MQTM. */
char struct_id[4];
/** The version number of this structure. Must be 0 or 1
* 0 indicates no message properties */
int struct_version;
/** The length of the MQTT message payload in bytes. */
int payloadlen;
/** A pointer to the payload of the MQTT message. */
void* payload;
/**
* The quality of service (QoS) assigned to the message.
* There are three levels of QoS:
* <DL>
* <DT><B>QoS0</B></DT>
* <DD>Fire and forget - the message may not be delivered</DD>
* <DT><B>QoS1</B></DT>
* <DD>At least once - the message will be delivered, but may be
* delivered more than once in some circumstances.</DD>
* <DT><B>QoS2</B></DT>
* <DD>Once and one only - the message will be delivered exactly once.</DD>
* </DL>
*/
int qos;
/**
* The retained flag serves two purposes depending on whether the message
* it is associated with is being published or received.
*
* <b>retained = true</b><br>
* For messages being published, a true setting indicates that the MQTT
* server should retain a copy of the message. The message will then be
* transmitted to new subscribers to a topic that matches the message topic.
* For subscribers registering a new subscription, the flag being true
* indicates that the received message is not a new one, but one that has
* been retained by the MQTT server.
*
* <b>retained = false</b> <br>
* For publishers, this indicates that this message should not be retained
* by the MQTT server. For subscribers, a false setting indicates this is
* a normal message, received as a result of it being published to the
* server.
*/
int retained;
/**
* The dup flag indicates whether or not this message is a duplicate.
* It is only meaningful when receiving QoS1 messages. When true, the
* client application should take appropriate action to deal with the
* duplicate message.
*/
int dup;
/** The message identifier is normally reserved for internal use by the
* MQTT client and server.
*/
int msgid;
/**
* The MQTT V5 properties associated with the message.
*/
MQTTProperties properties;
} MQTTClient_message;
#define MQTTClient_message_initializer { {'M', 'Q', 'T', 'M'}, 1, 0, NULL, 0, 0, 0, 0, MQTTProperties_initializer }
/**
* This is a callback function. The client application
* must provide an implementation of this function to enable asynchronous
* receipt of messages. The function is registered with the client library by
* passing it as an argument to MQTTClient_setCallbacks(). It is
* called by the client library when a new message that matches a client
* subscription has been received from the server. This function is executed on
* a separate thread to the one on which the client application is running.
* @param context A pointer to the <i>context</i> value originally passed to
* MQTTClient_setCallbacks(), which contains any application-specific context.
* @param topicName The topic associated with the received message.
* @param topicLen The length of the topic if there are one
* more NULL characters embedded in <i>topicName</i>, otherwise <i>topicLen</i>
* is 0. If <i>topicLen</i> is 0, the value returned by <i>strlen(topicName)</i>
* can be trusted. If <i>topicLen</i> is greater than 0, the full topic name
* can be retrieved by accessing <i>topicName</i> as a byte array of length
* <i>topicLen</i>.
* @param message The MQTTClient_message structure for the received message.
* This structure contains the message payload and attributes.
* @return This function must return 0 or 1 indicating whether or not
* the message has been safely received by the client application. <br>
* Returning 1 indicates that the message has been successfully handled.
* To free the message storage, ::MQTTClient_freeMessage must be called.
* To free the topic name storage, ::MQTTClient_free must be called.<br>
* Returning 0 indicates that there was a problem. In this
* case, the client library will reinvoke MQTTClient_messageArrived() to
* attempt to deliver the message to the application again.
* Do not free the message and topic storage when returning 0, otherwise
* the redelivery will fail.
*/
typedef int MQTTClient_messageArrived(void* context, char* topicName, int topicLen, MQTTClient_message* message);
/**
* This is a callback function. The client application
* must provide an implementation of this function to enable asynchronous
* notification of delivery of messages. The function is registered with the
* client library by passing it as an argument to MQTTClient_setCallbacks().
* It is called by the client library after the client application has
* published a message to the server. It indicates that the necessary
* handshaking and acknowledgements for the requested quality of service (see
* MQTTClient_message.qos) have been completed. This function is executed on a
* separate thread to the one on which the client application is running.
* <b>Note:</b>MQTTClient_deliveryComplete() is not called when messages are
* published at QoS0.
* @param context A pointer to the <i>context</i> value originally passed to
* MQTTClient_setCallbacks(), which contains any application-specific context.
* @param dt The ::MQTTClient_deliveryToken associated with
* the published message. Applications can check that all messages have been
* correctly published by matching the delivery tokens returned from calls to
* MQTTClient_publish() and MQTTClient_publishMessage() with the tokens passed
* to this callback.
*/
typedef void MQTTClient_deliveryComplete(void* context, MQTTClient_deliveryToken dt);
/**
* This is a callback function. The client application
* must provide an implementation of this function to enable asynchronous
* notification of the loss of connection to the server. The function is
* registered with the client library by passing it as an argument to
* MQTTClient_setCallbacks(). It is called by the client library if the client
* loses its connection to the server. The client application must take
* appropriate action, such as trying to reconnect or reporting the problem.
* This function is executed on a separate thread to the one on which the
* client application is running.
* @param context A pointer to the <i>context</i> value originally passed to
* MQTTClient_setCallbacks(), which contains any application-specific context.
* @param cause The reason for the disconnection.
* Currently, <i>cause</i> is always set to NULL.
*/
typedef void MQTTClient_connectionLost(void* context, char* cause);
/**
* 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 @ref async for more information.
*
* <b>Note:</b> The MQTT client must be disconnected when this function is
* called.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param context A pointer to any application-specific context. The
* the <i>context</i> pointer is passed to each of the callback functions to
* provide access to the context information in the callback.
* @param cl A pointer to an MQTTClient_connectionLost() callback
* function. You can set this to NULL if your application doesn't handle
* disconnections.
* @param 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.
* @param 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.
* @return ::MQTTCLIENT_SUCCESS if the callbacks were correctly set,
* ::MQTTCLIENT_FAILURE if an error occurred.
*/
LIBMQTT_API int MQTTClient_setCallbacks(MQTTClient handle, void* context, MQTTClient_connectionLost* cl,
MQTTClient_messageArrived* ma, MQTTClient_deliveryComplete* dc);
/**
* This is a callback function, which will be called when the a disconnect
* packet is received from the server. This applies to MQTT V5 and above only.
* @param context A pointer to the <i>context</i> value originally passed to
* ::MQTTClient_setDisconnected(), which contains any application-specific context.
* @param properties The MQTT V5 properties received with the disconnect, if any.
* @param reasonCode The MQTT V5 reason code received with the disconnect.
* Currently, <i>cause</i> is always set to NULL.
*/
typedef void MQTTClient_disconnected(void* context, MQTTProperties* properties,
enum MQTTReasonCodes reasonCode);
/**
* 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.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param context A pointer to any application-specific context. The
* the <i>context</i> pointer is passed to each of the callback functions to
* provide access to the context information in the callback.
* @param co A pointer to an MQTTClient_disconnected() callback
* function. NULL removes the callback setting.
* @return ::MQTTCLIENT_SUCCESS if the callbacks were correctly set,
* ::MQTTCLIENT_FAILURE if an error occurred.
*/
LIBMQTT_API int MQTTClient_setDisconnected(MQTTClient handle, void* context, MQTTClient_disconnected* co);
/**
* This is a callback function, the MQTT V5 version of MQTTClient_deliveryComplete().
* The client application
* must provide an implementation of this function to enable asynchronous
* notification of the completed delivery of messages.
* It is called by the client library after the client application has
* published a message to the server. It indicates that the necessary
* handshaking and acknowledgements for the requested quality of service (see
* MQTTClient_message.qos) have been completed. This function is executed on a
* separate thread to the one on which the client application is running.
* <b>Note:</b> It is not called when messages are published at QoS0.
* @param context A pointer to the <i>context</i> value originally passed to
* MQTTClient_setCallbacks(), which contains any application-specific context.
* @param dt The ::MQTTClient_deliveryToken associated with
* the published message. Applications can check that all messages have been
* correctly published by matching the delivery tokens returned from calls to
* MQTTClient_publish() and MQTTClient_publishMessage() with the tokens passed
* to this callback.
* @param packet_type the last received packet type for this completion. For QoS 1
* always PUBACK. For QoS 2 could be PUBREC or PUBCOMP.
* @param properties the MQTT V5 properties returned with the last packet from the server
* @param reasonCode the reason code returned from the server
*/
typedef void MQTTClient_published(void* context, int dt, int packet_type, MQTTProperties* properties,
enum MQTTReasonCodes reasonCode);
LIBMQTT_API int MQTTClient_setPublished(MQTTClient handle, void* context, MQTTClient_published* co);
/**
* 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().
* @param handle A pointer to an ::MQTTClient handle. The handle is
* populated with a valid client reference following a successful return from
* this function.
* @param serverURI A null-terminated string specifying the server to
* which the client will connect. It takes the form <i>protocol://host:port</i>.
* Currently, <i>protocol</i> must be:
* <br>
* @em tcp:// or @em mqtt:// - Insecure TCP
* <br>
* @em ssl:// or @em mqtts:// - Encrypted SSL/TLS
* <br>
* @em ws:// - Insecure websockets
* <br>
* @em wss:// - Secure web sockets
* <br>
* The TLS enabled prefixes (ssl, mqtts, wss) are only valid if a TLS
* version of the library is linked with.
* For <i>host</i>, 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 <i>tcp://localhost:1883</i>.
* @param clientId The client identifier passed to the server when the
* client connects to it. It is a null-terminated UTF-8 encoded string.
* @param persistence_type The type of persistence to be used by the client:
* <br>
* ::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.
* <br>
* ::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.
* <br>
* ::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.
* @param 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.
* @return ::MQTTCLIENT_SUCCESS if the client is successfully created, otherwise
* an error code is returned.
*/
LIBMQTT_API int MQTTClient_create(MQTTClient* handle, const char* serverURI, const char* clientId,
int persistence_type, void* persistence_context);
/** Options for the ::MQTTClient_createWithOptions call */
typedef struct
{
/** The eyecatcher for this structure. must be MQCO. */
char struct_id[4];
/** The version number of this structure. Must be 0 */
int struct_version;
/** Whether the MQTT version is 3.1, 3.1.1, or 5. To use V5, this must be set.
* MQTT V5 has to be chosen here, because during the create call the message persistence
* is initialized, and we want to know whether the format of any persisted messages
* is appropriate for the MQTT version we are going to connect with. Selecting 3.1 or
* 3.1.1 and attempting to read 5.0 persisted messages will result in an error on create. */
int MQTTVersion;
} MQTTClient_createOptions;
#define MQTTClient_createOptions_initializer { {'M', 'Q', 'C', 'O'}, 0, MQTTVERSION_DEFAULT }
/**
* 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().
* @param handle A pointer to an ::MQTTClient handle. The handle is
* populated with a valid client reference following a successful return from
* this function.
* @param serverURI A null-terminated string specifying the server to
* which the client will connect. It takes the form <i>protocol://host:port</i>.
* Currently, <i>protocol</i> must be <i>tcp</i> or <i>ssl</i>.
* For <i>host</i>, 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
* <i>tcp://localhost:1883</i>.
* @param clientId The client identifier passed to the server when the
* client connects to it. It is a null-terminated UTF-8 encoded string.
* @param persistence_type The type of persistence to be used by the client:
* <br>
* ::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.
* <br>
* ::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.
* <br>
* ::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.
* @param 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.
* @param options additional options for the create.
* @return ::MQTTCLIENT_SUCCESS if the client is successfully created, otherwise
* an error code is returned.
*/
LIBMQTT_API int MQTTClient_createWithOptions(MQTTClient* handle, const char* serverURI, const char* clientId,
int persistence_type, void* persistence_context, MQTTClient_createOptions* options);
/**
* MQTTClient_willOptions defines the MQTT "Last Will and Testament" (LWT) settings for
* the client. In the event that a client unexpectedly loses its connection to
* the server, the server publishes the LWT message to the LWT topic on
* behalf of the client. This allows other clients (subscribed to the LWT topic)
* to be made aware that the client has disconnected. To enable the LWT
* function for a specific client, a valid pointer to an MQTTClient_willOptions
* structure is passed in the MQTTClient_connectOptions structure used in the
* MQTTClient_connect() call that connects the client to the server. The pointer
* to MQTTClient_willOptions can be set to NULL if the LWT function is not
* required.
*/
typedef struct
{
/** The eyecatcher for this structure. must be MQTW. */
char struct_id[4];
/** The version number of this structure. Must be 0 or 1
0 means there is no binary payload option
*/
int struct_version;
/** The LWT topic to which the LWT message will be published. */
const char* topicName;
/** The LWT payload in string form. */
const char* message;
/**
* The retained flag for the LWT message (see MQTTClient_message.retained).
*/
int retained;
/**
* The quality of service setting for the LWT message (see
* MQTTClient_message.qos and @ref qos).
*/
int qos;
/** The LWT payload in binary form. This is only checked and used if the message option is NULL */
struct
{
int len; /**< binary payload length */
const void* data; /**< binary payload data */
} payload;
} MQTTClient_willOptions;
#define MQTTClient_willOptions_initializer { {'M', 'Q', 'T', 'W'}, 1, NULL, NULL, 0, 0, {0, NULL} }
#define MQTT_SSL_VERSION_DEFAULT 0
#define MQTT_SSL_VERSION_TLS_1_0 1
#define MQTT_SSL_VERSION_TLS_1_1 2
#define MQTT_SSL_VERSION_TLS_1_2 3
/**
* MQTTClient_sslProperties defines the settings to establish an SSL/TLS connection using the
* OpenSSL library. It covers the following scenarios:
* - Server authentication: The client needs the digital certificate of the server. It is included
* in a store containting trusted material (also known as "trust store").
* - Mutual authentication: Both client and server are authenticated during the SSL handshake. In
* addition to the digital certificate of the server in a trust store, the client will need its own
* digital certificate and the private key used to sign its digital certificate stored in a "key store".
* - Anonymous connection: Both client and server do not get authenticated and no credentials are needed
* to establish an SSL connection. Note that this scenario is not fully secure since it is subject to
* man-in-the-middle attacks.
*/
typedef struct
{
/** The eyecatcher for this structure. Must be MQTS */
char struct_id[4];
/** The version number of this structure. Must be 0, 1, 2, 3, 4 or 5.
* 0 means no sslVersion
* 1 means no verify, CApath
* 2 means no ssl_error_context, ssl_error_cb
* 3 means no ssl_psk_cb, ssl_psk_context, disableDefaultTrustStore
* 4 means no protos, protos_len
*/
int struct_version;
/** The file in PEM format containing the public digital certificates trusted by the client. */
const char* trustStore;
/** The file in PEM format containing the public certificate chain of the client. It may also include
* the client's private key.
*/
const char* keyStore;
/** If not included in the sslKeyStore, this setting points to the file in PEM format containing
* the client's private key.
*/
const char* privateKey;
/** The password to load the client's privateKey if encrypted. */
const char* privateKeyPassword;
/**
* The list of cipher suites that the client will present to the server during the SSL handshake. For a
* full explanation of the cipher list format, please see the OpenSSL on-line documentation:
* http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT
* If this setting is ommitted, its default value will be "ALL", that is, all the cipher suites -excluding
* those offering no encryption- will be considered.
* This setting can be used to set an SSL anonymous connection ("aNULL" string value, for instance).
*/
const char* enabledCipherSuites;
/** True/False option to enable verification of the server certificate **/
int enableServerCertAuth;
/** The SSL/TLS version to use. Specify one of MQTT_SSL_VERSION_DEFAULT (0),
* MQTT_SSL_VERSION_TLS_1_0 (1), MQTT_SSL_VERSION_TLS_1_1 (2) or MQTT_SSL_VERSION_TLS_1_2 (3).
* Only used if struct_version is >= 1.
*/
int sslVersion;
/**
* Whether to carry out post-connect checks, including that a certificate
* matches the given host name.
* Exists only if struct_version >= 2
*/
int verify;
/**
* From the OpenSSL documentation:
* If CApath is not NULL, it points to a directory containing CA certificates in PEM format.
* Exists only if struct_version >= 2
*/
const char* CApath;
/**
* Callback function for OpenSSL error handler ERR_print_errors_cb
* Exists only if struct_version >= 3
*/
int (*ssl_error_cb) (const char *str, size_t len, void *u);
/**
* Application-specific contex for OpenSSL error handler ERR_print_errors_cb
* Exists only if struct_version >= 3
*/
void* ssl_error_context;
/**
* Callback function for setting TLS-PSK options. Parameters correspond to that of
* SSL_CTX_set_psk_client_callback, except for u which is the pointer ssl_psk_context.
* Exists only if struct_version >= 4
*/
unsigned int (*ssl_psk_cb) (const char *hint, char *identity, unsigned int max_identity_len, unsigned char *psk, unsigned int max_psk_len, void *u);
/**
* Application-specific contex for ssl_psk_cb
* Exists only if struct_version >= 4
*/
void* ssl_psk_context;
/**
* Don't load default SSL CA. Should be used together with PSK to make sure
* regular servers with certificate in place is not accepted.
* Exists only if struct_version >= 4
*/
int disableDefaultTrustStore;
/**
* The protocol-lists must be in wire-format, which is defined as a vector of non-empty, 8-bit length-prefixed, byte strings.
* The length-prefix byte is not included in the length. Each string is limited to 255 bytes. A byte-string length of 0 is invalid.
* A truncated byte-string is invalid.
* Check documentation for SSL_CTX_set_alpn_protos
* Exists only if struct_version >= 5
*/
const unsigned char *protos;
/**
* The length of the vector protos vector
* Exists only if struct_version >= 5
*/
unsigned int protos_len;
} MQTTClient_SSLOptions;
#define MQTTClient_SSLOptions_initializer { {'M', 'Q', 'T', 'S'}, 5, NULL, NULL, NULL, NULL, NULL, 1, MQTT_SSL_VERSION_DEFAULT, 0, NULL, NULL, NULL, NULL, NULL, 0, NULL, 0 }
/**
* MQTTClient_libraryInfo is used to store details relating to the currently used
* library such as the version in use, the time it was built and relevant openSSL
* options.
* There is one static instance of this struct in MQTTClient.c
*/
typedef struct
{
const char* name;
const char* value;
} MQTTClient_nameValue;
/**
* This function returns version information about the library.
* no trace information will be returned.
* @return an array of strings describing the library. The last entry is a NULL pointer.
*/
LIBMQTT_API MQTTClient_nameValue* MQTTClient_getVersionInfo(void);
/**
* MQTTClient_connectOptions defines several settings that control the way the
* client connects to an MQTT server.
*
* <b>Note:</b> Default values are not defined for members of
* MQTTClient_connectOptions so it is good practice to specify all settings.
* If the MQTTClient_connectOptions structure is defined as an automatic
* variable, all members are set to random values and thus must be set by the
* client application. If the MQTTClient_connectOptions structure is defined
* as a static variable, initialization (in compliant compilers) sets all
* values to 0 (NULL for pointers). A #keepAliveInterval setting of 0 prevents
* correct operation of the client and so you <b>must</b> at least set a value
* for #keepAliveInterval.
*
* Suitable default values are set in the following initializers:
* - MQTTClient_connectOptions_initializer: for MQTT 3.1.1 non-WebSockets
* - MQTTClient_connectOptions_initializer5: for MQTT 5.0 non-WebSockets
* - MQTTClient_connectOptions_initializer_ws: for MQTT 3.1.1 WebSockets
* - MQTTClient_connectOptions_initializer5_ws: for MQTT 5.0 WebSockets
*/
typedef struct
{
/** The eyecatcher for this structure. must be MQTC. */
char struct_id[4];
/** The version number of this structure. Must be 0, 1, 2, 3, 4, 5, 6, 7 or 8.
* 0 signifies no SSL options and no serverURIs
* 1 signifies no serverURIs
* 2 signifies no MQTTVersion
* 3 signifies no returned values
* 4 signifies no binary password option
* 5 signifies no maxInflightMessages and cleanstart
* 6 signifies no HTTP headers option
* 7 signifies no HTTP proxy and HTTPS proxy options
*/
int struct_version;
/** The "keep alive" interval, measured in seconds, defines the maximum time
* that should pass without communication between the client and the server
* The client will ensure that at least one message travels across the
* network within each keep alive period. In the absence of a data-related
* message during the time period, the client sends a very small MQTT
* "ping" message, which the server will acknowledge. The keep alive
* interval enables the client to detect when the server is no longer
* available without having to wait for the long TCP/IP timeout.
*/
int keepAliveInterval;
/**
* This is a boolean value. The cleansession setting controls the behaviour
* of both the client and the server at connection and disconnection time.
* The client and server both maintain session state information. This
* information is used to ensure "at least once" and "exactly once"
* delivery, and "exactly once" receipt of messages. Session state also
* includes subscriptions created by an MQTT client. You can choose to
* maintain or discard state information between sessions.
*
* When cleansession is true, the state information is discarded at
* connect and disconnect. Setting cleansession to false keeps the state
* information. When you connect an MQTT client application with
* MQTTClient_connect(), the client identifies the connection using the
* client identifier and the address of the server. The server checks
* whether session information for this client
* has been saved from a previous connection to the server. If a previous
* session still exists, and cleansession=true, then the previous session
* information at the client and server is cleared. If cleansession=false,
* the previous session is resumed. If no previous session exists, a new
* session is started.
*/
int cleansession;
/**
* This is a boolean value that controls how many messages can be in-flight
* simultaneously. Setting <i>reliable</i> to true means that a published
* message must be completed (acknowledgements received) before another
* can be sent. Attempts to publish additional messages receive an
* ::MQTTCLIENT_MAX_MESSAGES_INFLIGHT return code. Setting this flag to
* false allows up to 10 messages to be in-flight. This can increase
* overall throughput in some circumstances.
*/
int reliable;
/**
* This is a pointer to an MQTTClient_willOptions structure. If your
* application does not make use of the Last Will and Testament feature,
* set this pointer to NULL.
*/
MQTTClient_willOptions* will;
/**
* MQTT servers that support the MQTT v3.1.1 protocol provide authentication
* and authorisation by user name and password. This is the user name
* parameter.
*/
const char* username;
/**
* MQTT servers that support the MQTT v3.1.1 protocol provide authentication
* and authorisation by user name and password. This is the password
* parameter.
*/
const char* password;
/**
* The time interval in seconds to allow a connect to complete.
*/
int connectTimeout;
/**
* The time interval in seconds after which unacknowledged publish requests are
* retried during a TCP session. With MQTT 3.1.1 and later, retries are
* not required except on reconnect. 0 turns off in-session retries, and is the
* recommended setting. Adding retries to an already overloaded network only
* exacerbates the problem.
*/
int retryInterval;
/**
* This is a pointer to an MQTTClient_SSLOptions structure. If your
* application does not make use of SSL, set this pointer to NULL.
*/
MQTTClient_SSLOptions* ssl;
/**
* The number of entries in the optional serverURIs array. Defaults to 0.
*/
int serverURIcount;
/**
* An optional array of null-terminated strings specifying the servers to
* which the client will connect. Each string takes the form <i>protocol://host:port</i>.
* <i>protocol</i> must be <i>tcp</i>, <i>ssl</i>, <i>ws</i> or <i>wss</i>.
* The TLS enabled prefixes (ssl, wss) are only valid if a TLS version of the library
* is linked with.
* For <i>host</i>, 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
* <i>tcp://localhost:1883</i>.
* If this list is empty (the default), the server URI specified on MQTTClient_create()
* is used.
*/
char* const* serverURIs;
/**
* Sets the version of MQTT to be used on the connect.
* MQTTVERSION_DEFAULT (0) = default: start with 3.1.1, and if that fails, fall back to 3.1
* MQTTVERSION_3_1 (3) = only try version 3.1
* MQTTVERSION_3_1_1 (4) = only try version 3.1.1
* MQTTVERSION_5 (5) = only try version 5.0
*/
int MQTTVersion;
/**
* Returned from the connect when the MQTT version used to connect is 3.1.1
*/
struct
{
const char* serverURI; /**< the serverURI connected to */
int MQTTVersion; /**< the MQTT version used to connect with */
int sessionPresent; /**< if the MQTT version is 3.1.1, the value of sessionPresent returned in the connack */
} returned;
/**
* Optional binary password. Only checked and used if the password option is NULL
*/
struct
{
int len; /**< binary password length */
const void* data; /**< binary password data */
} binarypwd;
/**
* The maximum number of messages in flight
*/
int maxInflightMessages;
/*
* MQTT V5 clean start flag. Only clears state at the beginning of the session.
*/
int cleanstart;
/**
* HTTP headers for websockets
*/
const MQTTClient_nameValue* httpHeaders;
/**
* HTTP proxy
*/
const char* httpProxy;
/**
* HTTPS proxy
*/
const char* httpsProxy;
} MQTTClient_connectOptions;
/** Initializer for connect options for MQTT 3.1.1 non-WebSocket connections */
#define MQTTClient_connectOptions_initializer { {'M', 'Q', 'T', 'C'}, 8, 60, 1, 1, NULL, NULL, NULL, 30, 0, NULL,\
0, NULL, MQTTVERSION_DEFAULT, {NULL, 0, 0}, {0, NULL}, -1, 0, NULL, NULL, NULL}
/** Initializer for connect options for MQTT 5.0 non-WebSocket connections */
#define MQTTClient_connectOptions_initializer5 { {'M', 'Q', 'T', 'C'}, 8, 60, 0, 1, NULL, NULL, NULL, 30, 0, NULL,\
0, NULL, MQTTVERSION_5, {NULL, 0, 0}, {0, NULL}, -1, 1, NULL, NULL, NULL}
/** Initializer for connect options for MQTT 3.1.1 WebSockets connections.
* The keepalive interval is set to 45 seconds to avoid webserver 60 second inactivity timeouts.
*/
#define MQTTClient_connectOptions_initializer_ws { {'M', 'Q', 'T', 'C'}, 8, 45, 1, 1, NULL, NULL, NULL, 30, 0, NULL,\
0, NULL, MQTTVERSION_DEFAULT, {NULL, 0, 0}, {0, NULL}, -1, 0, NULL, NULL, NULL}
/** Initializer for connect options for MQTT 5.0 WebSockets connections.
* The keepalive interval is set to 45 seconds to avoid webserver 60 second inactivity timeouts.
*/
#define MQTTClient_connectOptions_initializer5_ws { {'M', 'Q', 'T', 'C'}, 8, 45, 0, 1, NULL, NULL, NULL, 30, 0, NULL,\
0, NULL, MQTTVERSION_5, {NULL, 0, 0}, {0, NULL}, -1, 1, NULL, NULL, NULL}
/**
* 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().
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param options A pointer to a valid MQTTClient_connectOptions
* structure.
* @return ::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:<br><br>
* <b>1</b>: Connection refused: Unacceptable protocol version<br>
* <b>2</b>: Connection refused: Identifier rejected<br>
* <b>3</b>: Connection refused: Server unavailable<br>
* <b>4</b>: Connection refused: Bad user name or password<br>
* <b>5</b>: Connection refused: Not authorized<br>
* <b>6-255</b>: Reserved for future use<br>
*/
LIBMQTT_API int MQTTClient_connect(MQTTClient handle, MQTTClient_connectOptions* options);
/** MQTT version 5.0 response information */
typedef struct MQTTResponse
{
int version; /* the version number of this structure */
enum MQTTReasonCodes reasonCode; /* the MQTT 5.0 reason code returned */
int reasonCodeCount; /* the number of reason codes. Used for subscribeMany5 and unsubscribeMany5 */
enum MQTTReasonCodes* reasonCodes; /* a list of reason codes. Used for subscribeMany5 and unsubscribeMany5 */
MQTTProperties* properties; /* optionally, the MQTT 5.0 properties returned */
} MQTTResponse;
#define MQTTResponse_initializer {1, MQTTREASONCODE_SUCCESS, 0, NULL, NULL}
/**
* Frees the storage associated with the MQTT response.
* @param response the response structure to be freed
*/
LIBMQTT_API void MQTTResponse_free(MQTTResponse response);
/**
* 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().
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param options A pointer to a valid MQTTClient_connectOptions
* structure.
* @param connectProperties the MQTT 5.0 connect properties to use
* @param willProperties the MQTT 5.0 properties to set on the will message
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_connect5(MQTTClient handle, MQTTClient_connectOptions* options,
MQTTProperties* connectProperties, MQTTProperties* willProperties);
/**
* 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()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param timeout The client delays disconnection for up to this time (in
* milliseconds) in order to allow in-flight message transfers to complete.
* @return ::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
*/
LIBMQTT_API int MQTTClient_disconnect(MQTTClient handle, int timeout);
LIBMQTT_API int MQTTClient_disconnect5(MQTTClient handle, int timeout, enum MQTTReasonCodes reason, MQTTProperties* props);
/**
* This function allows the client application to test whether or not a
* client is currently connected to the MQTT server.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @return Boolean true if the client is connected, otherwise false.
*/
LIBMQTT_API int MQTTClient_isConnected(MQTTClient handle);
/* Subscribe is synchronous. QoS list parameter is changed on return to granted QoSs.
Returns return code, MQTTCLIENT_SUCCESS == success, non-zero some sort of error (TBD) */
/**
* This function attempts to subscribe a client to a single topic, which may
* contain wildcards (see @ref wildcard). This call also specifies the
* @ref qos requested for the subscription
* (see also MQTTClient_subscribeMany()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topic The subscription topic, which may include wildcards.
* @param qos The requested quality of service for the subscription.
* @return ::MQTTCLIENT_SUCCESS if the subscription request is successful.
* An error code is returned if there was a problem registering the
* subscription.
*/
LIBMQTT_API int MQTTClient_subscribe(MQTTClient handle, const char* topic, int qos);
/**
* This function attempts to subscribe an MQTT version 5.0 client to a single topic, which may
* contain wildcards (see @ref wildcard). This call also specifies the
* @ref qos requested for the subscription
* (see also MQTTClient_subscribeMany()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topic The subscription topic, which may include wildcards.
* @param qos The requested quality of service for the subscription.
* @param opts the MQTT 5.0 subscribe options to be used
* @param props the MQTT 5.0 properties to be used
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_subscribe5(MQTTClient handle, const char* topic, int qos,
MQTTSubscribe_options* opts, MQTTProperties* props);
/**
* This function attempts to subscribe a client to a list of topics, which may
* contain wildcards (see @ref wildcard). This call also specifies the
* @ref qos requested for each topic (see also MQTTClient_subscribe()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param count The number of topics for which the client is requesting
* subscriptions.
* @param topic An array (of length <i>count</i>) of pointers to
* topics, each of which may include wildcards.
* @param qos An array (of length <i>count</i>) of @ref qos
* values. qos[n] is the requested QoS for topic[n].
* @return ::MQTTCLIENT_SUCCESS if the subscription request is successful.
* An error code is returned if there was a problem registering the
* subscriptions.
*/
LIBMQTT_API int MQTTClient_subscribeMany(MQTTClient handle, int count, char* const* topic, int* qos);
/**
* This function attempts to subscribe an MQTT version 5.0 client to a list of topics, which may
* contain wildcards (see @ref wildcard). This call also specifies the
* @ref qos requested for each topic (see also MQTTClient_subscribe()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param count The number of topics for which the client is requesting
* subscriptions.
* @param topic An array (of length <i>count</i>) of pointers to
* topics, each of which may include wildcards.
* @param qos An array (of length <i>count</i>) of @ref qos
* values. qos[n] is the requested QoS for topic[n].
* @param opts the MQTT 5.0 subscribe options to be used
* @param props the MQTT 5.0 properties to be used
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_subscribeMany5(MQTTClient handle, int count, char* const* topic,
int* qos, MQTTSubscribe_options* opts, MQTTProperties* props);
/**
* This function attempts to remove an existing subscription made by the
* specified client.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topic The topic for the subscription to be removed, which may
* include wildcards (see @ref wildcard).
* @return ::MQTTCLIENT_SUCCESS if the subscription is removed.
* An error code is returned if there was a problem removing the
* subscription.
*/
LIBMQTT_API int MQTTClient_unsubscribe(MQTTClient handle, const char* topic);
/**
* This function attempts to remove an existing subscription made by the
* specified client using MQTT 5.0.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topic The topic for the subscription to be removed, which may
* include wildcards (see @ref wildcard).
* @param props the MQTT 5.0 properties to be used
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_unsubscribe5(MQTTClient handle, const char* topic, MQTTProperties* props);
/**
* This function attempts to remove existing subscriptions to a list of topics
* made by the specified client.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param count The number subscriptions to be removed.
* @param topic An array (of length <i>count</i>) of pointers to the topics of
* the subscriptions to be removed, each of which may include wildcards.
* @return ::MQTTCLIENT_SUCCESS if the subscriptions are removed.
* An error code is returned if there was a problem removing the subscriptions.
*/
LIBMQTT_API 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 using MQTT version 5.0.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param count The number subscriptions to be removed.
* @param topic An array (of length <i>count</i>) of pointers to the topics of
* the subscriptions to be removed, each of which may include wildcards.
* @param props the MQTT 5.0 properties to be used
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_unsubscribeMany5(MQTTClient handle, int count, char* const* topic, MQTTProperties* props);
/**
* 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 @ref async,
* ::MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topicName The topic associated with this message.
* @param payloadlen The length of the payload in bytes.
* @param payload A pointer to the byte array payload of the message.
* @param qos The @ref qos of the message.
* @param retained The retained flag for the message.
* @param 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.
* @return ::MQTTCLIENT_SUCCESS if the message is accepted for publication.
* An error code is returned if there was a problem accepting the message.
*/
LIBMQTT_API int MQTTClient_publish(MQTTClient handle, const char* topicName, int payloadlen, const void* payload, int qos, int retained,
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 @ref async,
* ::MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topicName The topic associated with this message.
* @param payloadlen The length of the payload in bytes.
* @param payload A pointer to the byte array payload of the message.
* @param qos The @ref qos of the message.
* @param retained The retained flag for the message.
* @param properties the MQTT 5.0 properties to be used
* @param 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.
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_publish5(MQTTClient handle, const char* topicName, int payloadlen, const void* payload,
int qos, int retained, MQTTProperties* properties, 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 @ref async,
* ::MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topicName The topic associated with this message.
* @param msg A pointer to a valid MQTTClient_message structure containing
* the payload and attributes of the message to be published.
* @param 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.
* @return ::MQTTCLIENT_SUCCESS if the message is accepted for publication.
* An error code is returned if there was a problem accepting the message.
*/
LIBMQTT_API int MQTTClient_publishMessage(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 @ref async,
* ::MQTTClient_waitForCompletion and MQTTClient_deliveryComplete()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param topicName The topic associated with this message.
* @param msg A pointer to a valid MQTTClient_message structure containing
* the payload and attributes of the message to be published.
* @param 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.
* @return the MQTT 5.0 response information: error codes and properties.
*/
LIBMQTT_API MQTTResponse MQTTClient_publishMessage5(MQTTClient handle, const char* topicName, MQTTClient_message* msg,
MQTTClient_deliveryToken* dt);
/**
* 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 @ref async.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param 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().
* @param timeout The maximum time to wait in milliseconds.
* @return ::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.
*/
LIBMQTT_API int MQTTClient_waitForCompletion(MQTTClient handle, MQTTClient_deliveryToken dt, unsigned long timeout);
/**
* This function sets a pointer to an array of delivery tokens for
* messages that are currently in-flight (pending completion).
*
* <b>Important note:</b> 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.
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param 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.
* @return ::MQTTCLIENT_SUCCESS if the function returns successfully.
* An error code is returned if there was a problem obtaining the list of
* pending tokens.
*/
LIBMQTT_API int MQTTClient_getPendingDeliveryTokens(MQTTClient handle, MQTTClient_deliveryToken **tokens);
/**
* 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.
*/
LIBMQTT_API void MQTTClient_yield(void);
/**
* 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 @ref 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()).
*
* <b>Important note:</b> The application must free() the memory allocated
* to the topic and the message when processing is complete (see
* MQTTClient_freeMessage()).
* @param handle A valid client handle from a successful call to
* MQTTClient_create().
* @param 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 <i>topicName</i> to point to the topic.
* @param 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
* <i>topicLen</i>.
* @param 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 <i>message</i> to point to the received message.
* The pointer is set to NULL if the timeout expires.
* @param timeout The length of time to wait for a message in milliseconds.
* @return ::MQTTCLIENT_SUCCESS or ::MQTTCLIENT_TOPICNAME_TRUNCATED if a
* message is received. ::MQTTCLIENT_SUCCESS can also indicate that the
* timeout expired, in which case <i>message</i> is NULL. An error code is
* returned if there was a problem trying to receive a message.
*/
LIBMQTT_API int MQTTClient_receive(MQTTClient handle, char** topicName, int* topicLen, MQTTClient_message** message,
unsigned long timeout);
/**
* 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. <b>Important
* note:</b> 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.
* @param msg The address of a pointer to the ::MQTTClient_message structure
* to be freed.
*/
LIBMQTT_API void MQTTClient_freeMessage(MQTTClient_message** msg);
/**
* 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.
* @param ptr The pointer to the client library storage to be freed.
*/
LIBMQTT_API void MQTTClient_free(void* ptr);
/**
* This function frees the memory allocated to an MQTT client (see
* MQTTClient_create()). It should be called when the client is no longer
* required.
* @param handle A pointer to the handle referring to the ::MQTTClient
* structure to be freed.
*/
LIBMQTT_API void MQTTClient_destroy(MQTTClient* handle);
enum MQTTCLIENT_TRACE_LEVELS
{
MQTTCLIENT_TRACE_MAXIMUM = 1,
MQTTCLIENT_TRACE_MEDIUM,
MQTTCLIENT_TRACE_MINIMUM,
MQTTCLIENT_TRACE_PROTOCOL,
MQTTCLIENT_TRACE_ERROR,
MQTTCLIENT_TRACE_SEVERE,
MQTTCLIENT_TRACE_FATAL,
};
/**
* This function sets the level of trace information which will be
* returned in the trace callback.
* @param level the trace level required
*/
LIBMQTT_API void MQTTClient_setTraceLevel(enum MQTTCLIENT_TRACE_LEVELS level);
/**
* This is a callback function prototype which must be implemented if you want
* to receive trace information. Do not invoke any other Paho API calls in this
* callback function - unpredictable behavior may result.
* @param level the trace level of the message returned
* @param message the trace message. This is a pointer to a static buffer which
* will be overwritten on each call. You must copy the data if you want to keep
* it for later.
*/
typedef void MQTTClient_traceCallback(enum MQTTCLIENT_TRACE_LEVELS level, char* message);
/**
* 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.
* @param callback a pointer to the function which will handle the trace information
*/
LIBMQTT_API void MQTTClient_setTraceCallback(MQTTClient_traceCallback* callback);
/**
* 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.
* @param handle A valid client handle from a successful call to MQTTClient_create().
* @param milliSeconds the maximum number of milliseconds to wait
* @return MQTTCLIENT_SUCCESS or MQTTCLIENT_FAILURE
*/
LIBMQTT_API int MQTTClient_setCommandTimeout(MQTTClient handle, unsigned long milliSeconds);
/**
* 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.
*/
LIBMQTT_API const char* MQTTClient_strerror(int code);
#if defined(__cplusplus)
}
#endif
#endif
/*!
* @cond MQTTClient_main
* @page async Asynchronous vs synchronous client applications
* This client library supports two modes of operation. These are referred to
* as <b>synchronous</b> and <b>asynchronous</b> modes. If your application
* calls MQTTClient_setCallbacks(), this puts the client into asynchronous
* mode, otherwise it operates in synchronous mode.
*
* In synchronous mode, the client application runs on a single thread.
* Messages are published using the MQTTClient_publish() and
* MQTTClient_publishMessage() functions. To determine that a QoS1 or QoS2
* (see @ref qos) message has been successfully delivered, the application
* must call the MQTTClient_waitForCompletion() function. An example showing
* synchronous publication is shown in @ref pubsync. Receiving messages in
* synchronous mode uses the MQTTClient_receive() function. Client applications
* must call either MQTTClient_receive() or MQTTClient_yield() relatively
* frequently in order to allow processing of acknowledgements and the MQTT
* "pings" that keep the network connection to the server alive.
*
* In asynchronous mode, the client application runs on several threads. The
* main program calls functions in the client library to publish and subscribe,
* just as for the synchronous mode. Processing of handshaking and maintaining
* the network connection is performed in the background, however.
* Notifications of status and message reception are provided to the client
* application using callbacks registered with the library by the call to
* MQTTClient_setCallbacks() (see MQTTClient_messageArrived(),
* MQTTClient_connectionLost() and MQTTClient_deliveryComplete()).
* This API is not thread safe however - it is not possible to call it from multiple
* threads without synchronization. You can use the MQTTAsync API for that.
*
* @page callbacks Callbacks
* You must not call a function from this API from within a callback otherwise
* a deadlock might result. The only exception to this is the ability to call
* connect within the connection lost callback, to allow a reconnect.
*
* When using MQTT 5.0, you can also call connect from within the disconnected
* callback, which is invoked when the MQTT server sends a disconnect packet.
* This server behaviour is allowed in MQTT 5.0, but not in MQTT 3.1.1, so the
* disconnected callback will never be invoked if you use MQTT 3.1.1.
*
* In particular, you must make a publish call within the message arrived callback.
* These restrictions are all lifted in the
* <a href="../../MQTTAsync/html/index.html">MQTTAsync API</a>.
*
* If no callbacks are assigned, this will include the message arrived callback.
* This could be done if the application is a pure publisher, and does
* not subscribe to any topics. If however messages are received, and no message
* arrived callback is set, or receive not called, then those messages will accumulate
* and take up memory, as there is no place for them to be delivered.
* It is up to the application to protect against this situation.
*
* @page wildcard Subscription wildcards
* Every MQTT message includes a topic that classifies it. MQTT servers use
* topics to determine which subscribers should receive messages published to
* the server.
*
* Consider the server receiving messages from several environmental sensors.
* Each sensor publishes its measurement data as a message with an associated
* topic. Subscribing applications need to know which sensor originally
* published each received message. A unique topic is thus used to identify
* each sensor and measurement type. Topics such as SENSOR1TEMP,
* SENSOR1HUMIDITY, SENSOR2TEMP and so on achieve this but are not very
* flexible. If additional sensors are added to the system at a later date,
* subscribing applications must be modified to receive them.
*
* To provide more flexibility, MQTT supports a hierarchical topic namespace.
* This allows application designers to organize topics to simplify their
* management. Levels in the hierarchy are delimited by the '/' character,
* such as SENSOR/1/HUMIDITY. Publishers and subscribers use these
* hierarchical topics as already described.
*
* For subscriptions, two wildcard characters are supported:
* <ul>
* <li>A '#' character represents a complete sub-tree of the hierarchy and
* thus must be the last character in a subscription topic string, such as
* SENSOR/#. This will match any topic starting with SENSOR/, such as
* SENSOR/1/TEMP and SENSOR/2/HUMIDITY.</li>
* <li> A '+' character represents a single level of the hierarchy and is
* used between delimiters. For example, SENSOR/+/TEMP will match
* SENSOR/1/TEMP and SENSOR/2/TEMP.</li>
* </ul>
* Publishers are not allowed to use the wildcard characters in their topic
* names.
*
* Deciding on your topic hierarchy is an important step in your system design.
*
* @page qos Quality of service
* The MQTT protocol provides three qualities of service for delivering
* messages between clients and servers: "at most once", "at least once" and
* "exactly once".
*
* Quality of service (QoS) is an attribute of an individual message being
* published. An application sets the QoS for a specific message by setting the
* MQTTClient_message.qos field to the required value.
*
* A subscribing client can set the maximum quality of service a server uses
* to send messages that match the client subscriptions. The
* MQTTClient_subscribe() and MQTTClient_subscribeMany() functions set this
* maximum. The QoS of a message forwarded to a subscriber thus might be
* different to the QoS given to the message by the original publisher.
* The lower of the two values is used to forward a message.
*
* The three levels are:
*
* <b>QoS0, At most once:</b> The message is delivered at most once, or it
* may not be delivered at all. Its delivery across the network is not
* acknowledged. The message is not stored. The message could be lost if the
* client is disconnected, or if the server fails. QoS0 is the fastest mode of
* transfer. It is sometimes called "fire and forget".
*
* The MQTT protocol does not require servers to forward publications at QoS0
* to a client. If the client is disconnected at the time the server receives
* the publication, the publication might be discarded, depending on the
* server implementation.
*
* <b>QoS1, At least once:</b> The message is always delivered at least once.
* It might be delivered multiple times if there is a failure before an
* acknowledgment is received by the sender. The message must be stored
* locally at the sender, until the sender receives confirmation that the
* message has been published by the receiver. The message is stored in case
* the message must be sent again.
*
* <b>QoS2, Exactly once:</b> The message is always delivered exactly once.
* The message must be stored locally at the sender, until the sender receives
* confirmation that the message has been published by the receiver. The
* message is stored in case the message must be sent again. QoS2 is the
* safest, but slowest mode of transfer. A more sophisticated handshaking
* and acknowledgement sequence is used than for QoS1 to ensure no duplication
* of messages occurs.
* @page pubsync Synchronous publication example
@code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#define ADDRESS "tcp://mqtt.eclipseprojects.io:1883"
#define CLIENTID "ExampleClientPub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to create client, return code %d\n", rc);
exit(EXIT_FAILURE);
}
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
pubmsg.payload = PAYLOAD;
pubmsg.payloadlen = (int)strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
if ((rc = MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to publish message, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Waiting for up to %d seconds for publication of %s\n"
"on topic %s for client with ClientID: %s\n",
(int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
printf("Message with delivery token %d delivered\n", token);
if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
printf("Failed to disconnect, return code %d\n", rc);
MQTTClient_destroy(&client);
return rc;
}
* @endcode
*
* @page pubasync Asynchronous publication example
@code{.c}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#if !defined(_WIN32)
#include <unistd.h>
#else
#include <windows.h>
#endif
#define ADDRESS "tcp://mqtt.eclipseprojects.io:1883"
#define CLIENTID "ExampleClientPub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
MQTTClient_deliveryToken deliveredtoken;
void delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery confirmed\n", dt);
deliveredtoken = dt;
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: %.*s\n", message->payloadlen, (char*)message->payload);
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to create client, return code %d\n", rc);
rc = EXIT_FAILURE;
goto exit;
}
if ((rc = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to set callbacks, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
pubmsg.payload = PAYLOAD;
pubmsg.payloadlen = (int)strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
deliveredtoken = 0;
if ((rc = MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to publish message, return code %d\n", rc);
rc = EXIT_FAILURE;
}
else
{
printf("Waiting for publication of %s\n"
"on topic %s for client with ClientID: %s\n",
PAYLOAD, TOPIC, CLIENTID);
while (deliveredtoken != token)
{
#if defined(_WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
}
}
if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to disconnect, return code %d\n", rc);
rc = EXIT_FAILURE;
}
destroy_exit:
MQTTClient_destroy(&client);
exit:
return rc;
}
* @endcode
* @page subasync Asynchronous subscription example
@code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#define ADDRESS "tcp://mqtt.eclipseprojects.io:1883"
#define CLIENTID "ExampleClientSub"
#define TOPIC "MQTT Examples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
volatile MQTTClient_deliveryToken deliveredtoken;
void delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery confirmed\n", dt);
deliveredtoken = dt;
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: %.*s\n", message->payloadlen, (char*)message->payload);
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
if ((rc = MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to create client, return code %d\n", rc);
rc = EXIT_FAILURE;
goto exit;
}
if ((rc = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to set callbacks, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
rc = EXIT_FAILURE;
goto destroy_exit;
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
if ((rc = MQTTClient_subscribe(client, TOPIC, QOS)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to subscribe, return code %d\n", rc);
rc = EXIT_FAILURE;
}
else
{
int ch;
do
{
ch = getchar();
} while (ch!='Q' && ch != 'q');
if ((rc = MQTTClient_unsubscribe(client, TOPIC)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to unsubscribe, return code %d\n", rc);
rc = EXIT_FAILURE;
}
}
if ((rc = MQTTClient_disconnect(client, 10000)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to disconnect, return code %d\n", rc);
rc = EXIT_FAILURE;
}
destroy_exit:
MQTTClient_destroy(&client);
exit:
return rc;
}
* @endcode
* @page tracing Tracing
*
* Runtime tracing is controlled by environment variables.
*
* Tracing is switched on by setting MQTT_C_CLIENT_TRACE. A value of ON, or stdout, prints to
* stdout, any other value is interpreted as a file name to use.
*
* The amount of trace detail is controlled with the MQTT_C_CLIENT_TRACE_LEVEL environment
* variable - valid values are ERROR, PROTOCOL, MINIMUM, MEDIUM and MAXIMUM
* (from least to most verbose).
*
* The variable MQTT_C_CLIENT_TRACE_MAX_LINES limits the number of lines of trace that are output
* to a file. Two files are used at most, when they are full, the last one is overwritten with the
* new trace entries. The default size is 1000 lines.
*
* ### MQTT Packet Tracing
*
* A feature that can be very useful is printing the MQTT packets that are sent and received. To
* achieve this, use the following environment variable settings:
* @code
MQTT_C_CLIENT_TRACE=ON
MQTT_C_CLIENT_TRACE_LEVEL=PROTOCOL
* @endcode
* The output you should see looks like this:
* @code
20130528 155936.813 3 stdout-subscriber -> CONNECT cleansession: 1 (0)
20130528 155936.813 3 stdout-subscriber <- CONNACK rc: 0
20130528 155936.813 3 stdout-subscriber -> SUBSCRIBE msgid: 1 (0)
20130528 155936.813 3 stdout-subscriber <- SUBACK msgid: 1
20130528 155941.818 3 stdout-subscriber -> DISCONNECT (0)
* @endcode
* where the fields are:
* 1. date
* 2. time
* 3. socket number
* 4. client id
* 5. direction (-> from client to server, <- from server to client)
* 6. packet details
*
* ### Default Level Tracing
*
* This is an extract of a default level trace of a call to connect:
* @code
19700101 010000.000 (1152206656) (0)> MQTTClient_connect:893
19700101 010000.000 (1152206656) (1)> MQTTClient_connectURI:716
20130528 160447.479 Connecting to serverURI localhost:1883
20130528 160447.479 (1152206656) (2)> MQTTProtocol_connect:98
20130528 160447.479 (1152206656) (3)> MQTTProtocol_addressPort:48
20130528 160447.479 (1152206656) (3)< MQTTProtocol_addressPort:73
20130528 160447.479 (1152206656) (3)> Socket_new:599
20130528 160447.479 New socket 4 for localhost, port 1883
20130528 160447.479 (1152206656) (4)> Socket_addSocket:163
20130528 160447.479 (1152206656) (5)> Socket_setnonblocking:73
20130528 160447.479 (1152206656) (5)< Socket_setnonblocking:78 (0)
20130528 160447.479 (1152206656) (4)< Socket_addSocket:176 (0)
20130528 160447.479 (1152206656) (4)> Socket_error:95
20130528 160447.479 (1152206656) (4)< Socket_error:104 (115)
20130528 160447.479 Connect pending
20130528 160447.479 (1152206656) (3)< Socket_new:683 (115)
20130528 160447.479 (1152206656) (2)< MQTTProtocol_connect:131 (115)
* @endcode
* where the fields are:
* 1. date
* 2. time
* 3. thread id
* 4. function nesting level
* 5. function entry (>) or exit (<)
* 6. function name : line of source code file
* 7. return value (if there is one)
*
* ### Memory Allocation Tracing
*
* Setting the trace level to maximum causes memory allocations and frees to be traced along with
* the default trace entries, with messages like the following:
* @code
20130528 161819.657 Allocating 16 bytes in heap at file /home/icraggs/workspaces/mqrtc/mqttv3c/src/MQTTPacket.c line 177 ptr 0x179f930
20130528 161819.657 Freeing 16 bytes in heap at file /home/icraggs/workspaces/mqrtc/mqttv3c/src/MQTTPacket.c line 201, heap use now 896 bytes
* @endcode
* When the last MQTT client object is destroyed, if the trace is being recorded
* and all memory allocated by the client library has not been freed, an error message will be
* written to the trace. This can help with fixing memory leaks. The message will look like this:
* @code
20130528 163909.208 Some memory not freed at shutdown, possible memory leak
20130528 163909.208 Heap scan start, total 880 bytes
20130528 163909.208 Heap element size 32, line 354, file /home/icraggs/workspaces/mqrtc/mqttv3c/src/MQTTPacket.c, ptr 0x260cb00
20130528 163909.208 Content
20130528 163909.209 Heap scan end
* @endcode
* @endcond
*/
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