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paho.mqtt.cpp/include/mqtt/async_client.h

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/////////////////////////////////////////////////////////////////////////////
/// @file async_client.h
/// Declaration of MQTT async_client class
/// @date May 1, 2013
/// @author Frank Pagliughi
/////////////////////////////////////////////////////////////////////////////
/*******************************************************************************
* Copyright (c) 2013-2024 Frank Pagliughi <fpagliughi@mindspring.com>
*
* 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
* http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Frank Pagliughi - initial implementation and documentation
* Frank Pagliughi - MQTT v5 support
*******************************************************************************/
#ifndef __mqtt_async_client_h
#define __mqtt_async_client_h
#include <functional>
#include <list>
#include <memory>
#include <stdexcept>
#include <tuple>
#include <vector>
#include "MQTTAsync.h"
#include "mqtt/callback.h"
#include "mqtt/create_options.h"
#include "mqtt/delivery_token.h"
#include "mqtt/exception.h"
#include "mqtt/iaction_listener.h"
#include "mqtt/iasync_client.h"
#include "mqtt/iclient_persistence.h"
#include "mqtt/message.h"
#include "mqtt/properties.h"
#include "mqtt/string_collection.h"
#include "mqtt/thread_queue.h"
#include "mqtt/token.h"
#include "mqtt/types.h"
namespace mqtt {
// OBSOLETE: The legacy constants that lacked the "PAHO_MQTTPP_" prefix
// clashed with #define's from other libraries and will be removed at the
// next major version upgrade.
#if defined(PAHO_MQTTPP_VERSIONS)
/** The version number for the client library. */
const uint32_t PAHO_MQTTPP_VERSION = 0x01050000;
/** The version string for the client library */
const string PAHO_MQTTPP_VERSION_STR("Paho MQTT C++ (mqttpp) v. 1.5.0");
/** Copyright notice for the client library */
const string PAHO_MQTTPP_COPYRIGHT("Copyright (c) 2013-2024 Frank Pagliughi");
#else
/** The version number for the client library. */
const uint32_t VERSION = 0x01050000;
/** The version string for the client library */
const string VERSION_STR("Paho MQTT C++ (mqttpp) v. 1.5.0");
/** Copyright notice for the client library */
const string COPYRIGHT("Copyright (c) 2013-2024 Frank Pagliughi");
#endif
/////////////////////////////////////////////////////////////////////////////
/**
* Client for talking to an MQTT server using non-blocking
* methods that allow an operation to run in the background.
*
* The location of the server is specified as a URI string with the
* following schemas supported to specify the type and security used for the
* connection:
* @li @em "mqtt://" - A standard (insecure) connection over TCP. (Also,
* "tcp://")
* @li @em "mqtts://" - A secure connection using SSL/TLS sockets. (Also
* "ssl://")
* @li @em "ws://" - A standard (insecure) WebSocket connection.
* @li @em "wss:// - A secure websocket connection using SSL/TLS.
*
* The secure connection types assume that the library was built with
* OpenSSL support, otherwise requesting a secure connection will result in
* an error.
*
* The communication methods of this class - `connect()`, `publish()`,
* `subscribe()`, etc. - are all asynchronous. They create the request for
* the server, but return immediately, before a response is received back
* from the server.
*
* These methods return a `Token` to the caller which is akin to a C++
* std::future. The caller can keep the Token, then use it later to block
* until the asynchronous operation is complete and retrieve the result of
* the operation, including any response from the server.
*
* Alternately, the application can choose to set callbacks to be fired when
* each operation completes. This can be used to create an event-driven
* architecture, but is more complex in that it forces the user to avoid any
* blocking operations and manually handle thread synchronization (since
* the callbacks run in a separate thread managed by the library).
*/
class async_client : public virtual iasync_client
{
public:
/** Smart/shared pointer for an object of this class */
using ptr_t = std::shared_ptr<async_client>;
/** Type for a thread-safe queue to consume messages synchronously */
using consumer_queue_type = std::unique_ptr<thread_queue<const_message_ptr>>;
/** Handler type for registering an individual message callback */
using message_handler = std::function<void(const_message_ptr)>;
/** Handler type for when a connection is made or lost */
using connection_handler = std::function<void(const string& cause)>;
/** Handler type for when a disconnect packet is received */
using disconnected_handler = std::function<void(const properties&, ReasonCode)>;
/** Handler for updating connection data before an auto-reconnect. */
using update_connection_handler = std::function<bool(connect_data&)>;
private:
/** Lock guard type for this class */
using guard = std::unique_lock<std::mutex>;
/** Unique lock type for this class */
using unique_lock = std::unique_lock<std::mutex>;
/** Object monitor mutex */
mutable std::mutex lock_;
/** The underlying C-lib client. */
MQTTAsync cli_;
/** The options used to create the client */
const create_options createOpts_;
/** The MQTT protocol version of the connection */
int mqttVersion_;
/** A user persistence wrapper (if any) */
std::unique_ptr<MQTTClient_persistence> persist_{};
/** Callback supplied by the user (if any) */
callback* userCallback_{};
/** Connection handler */
connection_handler connHandler_;
/** Connection lost handler */
connection_handler connLostHandler_;
/** Disconnected handler */
disconnected_handler disconnectedHandler_;
/** Update connect data/options */
update_connection_handler updateConnectionHandler_;
/** Message handler */
message_handler msgHandler_;
/** Cached options from the last connect */
connect_options connOpts_;
/** Copy of connect token (for re-connects) */
token_ptr connTok_;
/** A list of tokens that are in play */
std::list<token_ptr> pendingTokens_;
/** A list of delivery tokens that are in play */
std::list<delivery_token_ptr> pendingDeliveryTokens_;
/** A queue of messages for consumer API */
consumer_queue_type que_;
/** Callbacks from the C library */
static void on_connected(void* context, char* cause);
static void on_connection_lost(void* context, char* cause);
static void on_disconnected(
void* context, MQTTProperties* cprops, MQTTReasonCodes reasonCode
);
static int on_message_arrived(
void* context, char* topicName, int topicLen, MQTTAsync_message* msg
);
static void on_delivery_complete(void* context, MQTTAsync_token tok);
static int on_update_connection(void* context, MQTTAsync_connectData* cdata);
/** Manage internal list of active tokens */
friend class token;
virtual void add_token(token_ptr tok);
virtual void add_token(delivery_token_ptr tok);
virtual void remove_token(token* tok) override;
virtual void remove_token(token_ptr tok) { remove_token(tok.get()); }
void remove_token(delivery_token_ptr tok) { remove_token(tok.get()); }
/** Non-copyable */
async_client() = delete;
async_client(const async_client&) = delete;
async_client& operator=(const async_client&) = delete;
/** Checks a function return code and throws on error. */
static void check_ret(int rc) {
if (rc != MQTTASYNC_SUCCESS)
throw exception(rc);
}
/**
* Create an async_client that can be used to communicate with an MQTT
* server, which allows for off-line message buffering.
* This allows the caller to specify a user-defined persistence object,
* or use no persistence.
* @param opts The create options
* @throw exception if an argument is invalid
*/
void create();
public:
/**
* Create an async_client that can be used to communicate with an MQTT
* server.
* This uses file-based persistence in the specified directory.
* @param serverURI the address of the server to connect to, specified
* as a URI.
* @param clientId a client identifier that is unique on the server
* being connected to
* @throw exception if an argument is invalid
*/
explicit async_client(const string& serverURI, const string& clientId = string{})
: async_client(serverURI, clientId, NO_PERSISTENCE) {}
/**
* Create an async_client that can be used to communicate with an MQTT
* server.
* This allows the caller to specify a user-defined persistence object,
* or use no persistence.
* @param serverURI the address of the server to connect to, specified
* as a URI.
* @param clientId a client identifier that is unique on the server
* being connected to
* @param persistence The user persistence structure. If this is null,
* then no persistence is used.
* @throw exception if an argument is invalid
*/
async_client(
const string& serverURI, const string& clientId, const persistence_type& persistence
)
: createOpts_{serverURI, clientId, persistence} {
create();
}
/**
* Create an async_client that can be used to communicate with an MQTT
* server, which allows for off-line message buffering.
* This uses file-based persistence in the specified directory.
* @param serverURI the address of the server to connect to, specified
* as a URI.
* @param clientId a client identifier that is unique on the server
* being connected to
* @param maxBufferedMessages the maximum number of messages allowed to
* be buffered while not connected
* @param persistDir The directory to use for persistence data
* @throw exception if an argument is invalid
*/
async_client(
const string& serverURI, const string& clientId, int maxBufferedMessages,
const persistence_type& persistence
)
: createOpts_{serverURI, clientId, maxBufferedMessages, persistence} {
create();
}
/**
* Create an async_client that can be used to communicate with an MQTT
* server, which allows for off-line message buffering.
* This uses file-based persistence in the specified directory.
* @param serverURI the address of the server to connect to, specified
* as a URI.
* @param clientId a client identifier that is unique on the server
* being connected to
* @param opts The create options
* @param persistDir The directory to use for persistence data
* @throw exception if an argument is invalid
*/
async_client(
const string& serverURI, const string& clientId, const create_options& opts,
const persistence_type& persistence
)
: createOpts_{serverURI, clientId, opts, persistence} {
create();
}
/**
* Create an async_client that can be used to communicate with an MQTT
* server, which allows for off-line message buffering.
* This allows the caller to specify a user-defined persistence object,
* or use no persistence.
* @param opts The create options
* @throw exception if an argument is invalid
*/
async_client(const create_options& opts) : createOpts_{opts} { create(); }
/**
* Destructor
*/
~async_client() override;
/**
* Sets a callback listener to use for events that happen
* asynchronously.
* @param cb callback receiver which will be invoked for certain
* asynchronous events
*/
void set_callback(callback& cb) override;
/**
* Stops callbacks.
* This is not normally called by the application. It should be used
* cautiously as it may cause the application to lose messages.
*/
void disable_callbacks() override;
/**
* Callback for when a connection is made.
* @param cb Callback functor for when the connection is made.
*/
void set_connected_handler(connection_handler cb) /*override*/;
/**
* Callback for when a connection is lost.
* @param cb Callback functor for when the connection is lost.
*/
void set_connection_lost_handler(connection_handler cb) /*override*/;
/**
* Callback for when a disconnect packet is received from the server.
* @param cb Callback for when the disconnect packet is received.
*/
void set_disconnected_handler(disconnected_handler cb) /*override*/;
/**
* Sets the callback for when a message arrives from the broker.
* Note that the application can only have one message handler which can
* be installed individually using this method, or installled as a
* listener object.
* @param cb The callback functor to register with the library.
*/
void set_message_callback(message_handler cb) /*override*/;
/**
* Sets a callback to allow the application to update the connection
* data on automatic reconnects.
* @param cb The callback functor to register with the library.
*/
void set_update_connection_handler(update_connection_handler cb);
/**
* Connects to an MQTT server using the default options.
* @return token used to track and wait for the connect to complete. The
* token will be passed to any callback that has been set.
* @throw exception for non security related problems
* @throw security_exception for security related problems
*/
token_ptr connect() override;
/**
* Connects to an MQTT server using the provided connect options.
* @param options a set of connection parameters that override the
* defaults.
* @return token used to track and wait for the connect to complete. The
* token will be passed to any callback that has been set.
* @throw exception for non security related problems
* @throw security_exception for security related problems
*/
token_ptr connect(connect_options options) override;
/**
* Connects to an MQTT server using the specified options.
* @param options a set of connection parameters that override the
* defaults.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback listener that will be notified when the connect
* completes.
* @return token used to track and wait for the connect to complete. The
* token will be passed to any callback that has been set.
* @throw exception for non security related problems
* @throw security_exception for security related problems
*/
token_ptr connect(connect_options options, void* userContext, iaction_listener& cb)
override;
/**
*
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback listener that will be notified when the connect
* completes.
* @return token used to track and wait for the connect to complete. The
* token will be passed to any callback that has been set.
* @throw exception for non security related problems
* @throw security_exception for security related problems
*/
token_ptr connect(void* userContext, iaction_listener& cb) override {
return connect(connect_options{}, userContext, cb);
}
/**
* Reconnects the client using options from the previous connect.
* The client must have previously called connect() for this to work.
* @return token used to track the progress of the reconnect.
*/
token_ptr reconnect() override;
/**
* Disconnects from the server.
* @return token used to track and wait for the disconnect to complete.
* The token will be passed to any callback that has been set.
* @throw exception for problems encountered while disconnecting
*/
token_ptr disconnect() override { return disconnect(disconnect_options()); }
/**
* Disconnects from the server.
* @param opts Options for disconnecting.
* @return token used to track and wait for the disconnect to complete.
* The token will be passed to any callback that has been set.
* @throw exception for problems encountered while disconnecting
*/
token_ptr disconnect(disconnect_options opts) override;
/**
* Disconnects from the server.
* @param timeout the amount of time in milliseconds to allow for
* existing work to finish before disconnecting. A value
* of zero or less means the client will not quiesce.
* @return Token used to track and wait for disconnect to complete. The
* token will be passed to the callback methods if a callback is
* set.
* @throw exception for problems encountered while disconnecting
*/
token_ptr disconnect(int timeout) override {
return disconnect(disconnect_options(timeout));
}
/**
* Disconnects from the server.
* @param timeout the amount of time in milliseconds to allow for
* existing work to finish before disconnecting. A value
* of zero or less means the client will not quiesce.
* @return Token used to track and wait for disconnect to complete. The
* token will be passed to the callback methods if a callback is
* set.
* @throw exception for problems encountered while disconnecting
*/
template <class Rep, class Period>
token_ptr disconnect(const std::chrono::duration<Rep, Period>& timeout) {
// TODO: check range
return disconnect((int)to_milliseconds_count(timeout));
}
/**
* Disconnects from the server.
* @param timeout the amount of time in milliseconds to allow for
* existing work to finish before disconnecting. A value
* of zero or less means the client will not quiesce.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback listener that will be notified when the disconnect
* completes.
* @return token_ptr Token used to track and wait for disconnect to
* complete. The token will be passed to the callback methods if
* a callback is set.
* @throw exception for problems encountered while disconnecting
*/
token_ptr disconnect(int timeout, void* userContext, iaction_listener& cb) override;
/**
* Disconnects from the server.
* @param timeout the amount of time in milliseconds to allow for
* existing work to finish before disconnecting. A value
* of zero or less means the client will not quiesce.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback listener that will be notified when the disconnect
* completes.
* @return token_ptr Token used to track and wait for disconnect to
* complete. The token will be passed to the callback methods if
* a callback is set.
* @throw exception for problems encountered while disconnecting
*/
template <class Rep, class Period>
token_ptr disconnect(
const std::chrono::duration<Rep, Period>& timeout, void* userContext,
iaction_listener& cb
) {
// TODO: check range
return disconnect((int)to_milliseconds_count(timeout), userContext, cb);
}
/**
* Disconnects from the server.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback listener that will be notified when the disconnect
* completes.
* @return token_ptr Token used to track and wait for disconnect to
* complete. The token will be passed to the callback methods if
* a callback is set.
* @throw exception for problems encountered while disconnecting
*/
token_ptr disconnect(void* userContext, iaction_listener& cb) override {
return disconnect(0L, userContext, cb);
}
/**
* Returns the delivery token for the specified message ID.
* @return delivery_token
*/
delivery_token_ptr get_pending_delivery_token(int msgID) const override;
/**
* Returns the delivery tokens for any outstanding publish operations.
* @return delivery_token[]
*/
std::vector<delivery_token_ptr> get_pending_delivery_tokens() const override;
/**
* Returns the client ID used by this client.
* @return The client ID used by this client.
*/
string get_client_id() const override { return createOpts_.get_client_id(); }
/**
* Returns the address of the server used by this client.
* @return The server's address, as a URI String.
*/
string get_server_uri() const override { return createOpts_.get_server_uri(); }
/**
* Gets the MQTT version used by the client.
* @return The MQTT version used by the client
* @li MQTTVERSION_DEFAULT (0) = default: start with 3.1.1, and if
* that fails, fall back to 3.1
* @li MQTTVERSION_3_1 (3) = only try version 3.1
* @li MQTTVERSION_3_1_1 (4) = only try version 3.1.1
* @li MQTTVERSION_5 (5) = only try version 5
*/
int mqtt_version() const noexcept { return mqttVersion_; }
/**
* Gets a copy of the connect options that were last used in a request
* to connect to the broker.
* @returns The last connect options that were used.
*/
connect_options get_connect_options() const {
guard g(lock_);
return connOpts_;
}
/**
* Determines if this client is currently connected to the server.
* @return true if connected, false otherwise.
*/
bool is_connected() const override { return to_bool(MQTTAsync_isConnected(cli_)); }
/**
* Publishes a message to a topic on the server
* @param topic The topic to deliver the message to
* @param payload the bytes to use as the message payload
* @param n the number of bytes in the payload
* @param qos the Quality of Service to deliver the message at. Valid
* values are 0, 1 or 2.
* @param retained whether or not this message should be retained by the
* server.
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(
string_ref topic, const void* payload, size_t n, int qos, bool retained
) override;
/**
* Publishes a message to a topic on the server
* @param topic The topic to deliver the message to
* @param payload the bytes to use as the message payload
* @param n the number of bytes in the payload
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(string_ref topic, const void* payload, size_t n) override {
return publish(
std::move(topic), payload, n, message::DFLT_QOS, message::DFLT_RETAINED
);
}
/**
* Publishes a message to a topic on the server
* @param topic The topic to deliver the message to
* @param payload the bytes to use as the message payload
* @param qos the Quality of Service to deliver the message at. Valid
* values are 0, 1 or 2.
* @param retained whether or not this message should be retained by the
* server.
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(string_ref topic, binary_ref payload, int qos, bool retained)
override;
/**
* Publishes a message to a topic on the server
* @param topic The topic to deliver the message to
* @param payload the bytes to use as the message payload
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(string_ref topic, binary_ref payload) override {
return publish(
std::move(topic), std::move(payload), message::DFLT_QOS, message::DFLT_RETAINED
);
}
/**
* Publishes a message to a topic on the server
* @param topic The topic to deliver the message to
* @param payload the bytes to use as the message payload
* @param n the number of bytes in the payload
* @param qos the Quality of Service to deliver the message at. Valid
* values are 0, 1 or 2.
* @param retained whether or not this message should be retained by the
* server.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(
string_ref topic, const void* payload, size_t n, int qos, bool retained,
void* userContext, iaction_listener& cb
) override;
/**
* Publishes a message to a topic on the server Takes an Message
* message and delivers it to the server at the requested quality of
* service.
* @param msg the message to deliver to the server
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(const_message_ptr msg) override;
/**
* Publishes a message to a topic on the server.
* @param msg the message to deliver to the server
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb callback optional listener that will be notified when message
* delivery has completed to the requested quality of
* service
* @return token used to track and wait for the publish to complete. The
* token will be passed to callback methods if set.
*/
delivery_token_ptr publish(const_message_ptr msg, void* userContext, iaction_listener& cb)
override;
/**
* Subscribe to a topic, which may include wildcards.
* @param topicFilter the topic to subscribe to, which can include
* wildcards.
* @param qos The quality of service for the subscription
* @param opts The MQTT v5 subscribe options for the topic
* @param props The MQTT v5 properties.
* @return token used to track and wait for the subscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr subscribe(
const string& topicFilter, int qos,
const subscribe_options& opts = subscribe_options(),
const properties& props = properties()
) override;
/**
* Subscribe to a topic, which may include wildcards.
* @param topicFilter the topic to subscribe to, which can include
* wildcards.
* @param qos the maximum quality of service at which to subscribe.
* Messages published at a lower quality of service will be
* received at the published QoS. Messages published at a
* higher quality of service will be received using the QoS
* specified on the subscribe.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb listener that will be notified when subscribe has completed
* @param opts The MQTT v5 subscribe options for the topic
* @param props The MQTT v5 properties.
* @return token used to track and wait for the subscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr subscribe(
const string& topicFilter, int qos, void* userContext, iaction_listener& cb,
const subscribe_options& opts = subscribe_options(),
const properties& props = properties()
) override;
/**
* Subscribe to multiple topics, each of which may include wildcards.
* @param topicFilters
* @param qos the maximum quality of service at which to subscribe.
* Messages published at a lower quality of service will be
* received at the published QoS. Messages published at a
* higher quality of service will be received using the QoS
* specified on the subscribe.
* @param opts The MQTT v5 subscribe options (one for each topic)
* @param props The MQTT v5 properties.
* @return token used to track and wait for the subscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr subscribe(
const_string_collection_ptr topicFilters, const qos_collection& qos,
const std::vector<subscribe_options>& opts = std::vector<subscribe_options>(),
const properties& props = properties()
) override;
/**
* Subscribes to multiple topics, each of which may include wildcards.
* @param topicFilters
* @param qos the maximum quality of service at which to subscribe.
* Messages published at a lower quality of service will be
* received at the published QoS. Messages published at a
* higher quality of service will be received using the QoS
* specified on the subscribe.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb listener that will be notified when subscribe has completed
* @param opts The MQTT v5 subscribe options (one for each topic)
* @param props The MQTT v5 properties.
* @return token used to track and wait for the subscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr subscribe(
const_string_collection_ptr topicFilters, const qos_collection& qos,
void* userContext, iaction_listener& cb,
const std::vector<subscribe_options>& opts = std::vector<subscribe_options>(),
const properties& props = properties()
) override;
/**
* Requests the server unsubscribe the client from a topic.
* @param topicFilter the topic to unsubscribe from. It must match a
* topicFilter specified on an earlier subscribe.
* @param props The MQTT v5 properties.
* @return token used to track and wait for the unsubscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr unsubscribe(const string& topicFilter, const properties& props = properties())
override;
/**
* Requests the server unsubscribe the client from one or more topics.
* @param topicFilters one or more topics to unsubscribe from. Each
* topicFilter must match one specified on an
* earlier subscribe.
* @param props The MQTT v5 properties.
* @return token used to track and wait for the unsubscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr unsubscribe(
const_string_collection_ptr topicFilters, const properties& props = properties()
) override;
/**
* Requests the server unsubscribe the client from one or more topics.
* @param topicFilters
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb listener that will be notified when unsubscribe has
* completed
* @param props The MQTT v5 properties.
* @return token used to track and wait for the unsubscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr unsubscribe(
const_string_collection_ptr topicFilters, void* userContext, iaction_listener& cb,
const properties& props = properties()
) override;
/**
* Requests the server unsubscribe the client from a topics.
* @param topicFilter the topic to unsubscribe from. It must match a
* topicFilter specified on an earlier subscribe.
* @param userContext optional object used to pass context to the
* callback. Use @em nullptr if not required.
* @param cb listener that will be notified when unsubscribe has
* completed
* @param props The MQTT v5 properties.
* @return token used to track and wait for the unsubscribe to complete.
* The token will be passed to callback methods if set.
*/
token_ptr unsubscribe(
const string& topicFilter, void* userContext, iaction_listener& cb,
const properties& props = properties()
) override;
/**
* Start consuming messages.
* This initializes the client to receive messages through a queue that
* can be read synchronously.
*/
void start_consuming() override;
/**
* Stop consuming messages.
* This shuts down the internal callback and discards any unread
* messages.
*/
void stop_consuming() override;
/**
* Read the next message from the queue.
* This blocks until a new message arrives.
* @return The message and topic.
*/
const_message_ptr consume_message() override { return que_->get(); }
/**
* Try to read the next message from the queue without blocking.
* @param msg Pointer to the value to receive the message
* @return @em true is a message was read, @em false if no message was
* available.
*/
bool try_consume_message(const_message_ptr* msg) override { return que_->try_get(msg); }
/**
* Waits a limited time for a message to arrive.
* @param msg Pointer to the value to receive the message
* @param relTime The maximum amount of time to wait for a message.
* @return @em true if a message was read, @em false if a timeout
* occurred.
*/
template <typename Rep, class Period>
bool try_consume_message_for(
const_message_ptr* msg, const std::chrono::duration<Rep, Period>& relTime
) {
return que_->try_get_for(msg, relTime);
}
/**
* Waits a limited time for a message to arrive.
* @param relTime The maximum amount of time to wait for a message.
* @return A shared pointer to the message that was received. It will be
* empty on timeout.
*/
template <typename Rep, class Period>
const_message_ptr try_consume_message_for(
const std::chrono::duration<Rep, Period>& relTime
) {
const_message_ptr msg;
que_->try_get_for(&msg, relTime);
return msg;
}
/**
* Waits until a specific time for a message to appear.
* @param msg Pointer to the value to receive the message
* @param absTime The time point to wait until, before timing out.
* @return @em true if a message was read, @em false if a timeout
* occurred.
*/
template <class Clock, class Duration>
bool try_consume_message_until(
const_message_ptr* msg, const std::chrono::time_point<Clock, Duration>& absTime
) {
return que_->try_get_until(msg, absTime);
}
/**
* Waits until a specific time for a message to appear.
* @param absTime The time point to wait until, before timing out.
* @return The message, if read, an empty pointer if not.
*/
template <class Clock, class Duration>
const_message_ptr try_consume_message_until(
const std::chrono::time_point<Clock, Duration>& absTime
) {
const_message_ptr msg;
que_->try_get_until(&msg, absTime);
return msg;
}
};
/** Smart/shared pointer to an asynchronous MQTT client object */
using async_client_ptr = async_client::ptr_t;
/////////////////////////////////////////////////////////////////////////////
} // namespace mqtt
#endif // __mqtt_async_client_h
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