MQTT Class

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A lightweight, fully-featured MQTT client implementation.

Syntax

class ipworksmq.MQTT

Remarks

The MQTT class provides a lightweight, fully-featured MQTT client implementation with support for versions 3.1.1 and 5.0. The class supports plaintext and TLS-enabled connections over both standard TCP and WebSockets.

Connecting

When connecting to an MQTT server, the class sends the following information:

• The values of the client_id, clean_session, and keep_alive_interval properties.
• The value of the user property (if non-empty).
• The value of the password property (if non-empty).
• The values of the will_topic and will_message properties and the WillQOS and WillRetain configuration settings.
• MQTT 5 specific values from ClientTopicAliasMax, SessionExpInterval, ConnectProperties and WillProperties.

If clean_session is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to clean_session, save_session, and restore_session for more information about MQTT sessions and session state persistence; refer to will_topic, will_message, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example mqtt1.ClientId = "testClient"; mqtt1.CleanSession = true; mqtt1.KeepAliveInterval = 30; mqtt1.WillTopic = "wills/" + mqtt1.ClientId; mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!"; mqtt1.ConnectTo("mqtt.test-server.com", 1883);

Topic Subscriptions

When subscribing, pass one or more topic filters and QoS levels to indicate the topics to subscribe to and the desired QoS level(s). Topic filters may contain wildcards in order to match multiple topics on the server.

Subscribe Examples // Subscribed event handler. mqtt1.OnSubscribed += (s, e) => { if (e.ResponseCode <= 2) Console.WriteLine("Subscribed to " + e.TopicFilter + " at QoS " + e.QOS + "."); else Console.WriteLine("Failed to subscribe to " + e.TopicFilter + "."); }; // Basic, subscribe to some topic filters, all at the same QoS level. mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 2); // A bit more advanced, subscribe to the same topic filters, but at different QoS levels. mqtt1.Config("TopicQOSArray=1,2,2"); // The 0 is ignored here since we've specified individual QoS values explicitly. mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 0);

After subscribing to topics, any messages received will cause the on_message_in, and potentially also the on_message_ack, events to fire. Refer to those events for more information about processing steps for inbound messages.

When unsubscribing, pass the exact same topic filter that was used to subscribe.

Unsubscribe Example // Unsubscribe from topic filters; have to use the exact same strings as before. If this // was to be called after calling the code example shown for the Subscribe() method, we // would still be subscribed to the "home" topic filter. mqtt1.Unsubscribe("home/floor1/+/temperature,home/floor2/#");

Refer to subscribe and unsubscribe for more information about subscriptions and topic filters.

Publishing Messages

publish_message is used to publish a message with a string payload, while publish_data is used to publish a message with a raw data payload. Both also accept the name of a topic to publish to, and a QoS level at which to publish.

Publish Examples // Publish a simple string-based message. mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!"); // Publish a raw data message. byte[] catPicture = ...; mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);

Refer to publish_data and publish_message for more information about message publishing and processing steps for outbound messages, as well as topic naming.

MQTT 5 Notes

MQTT 5 is similar to v3.1.1, with a few changes and several new features. Major differences include:

• The Clean Session flag functionality is divided into two properties to allow for finer control over session state data: the Clean Start flag (see clean_session) and the new SessionExpInterval.
• All response packets (CONNACK, PUBACK, PUBREC, PUBREL, PUBCOMP, SUBACK, UNSUBACK, DISCONNECT) now contain a reason code describing why operations succeeded or failed. See on_message_ack, on_subscribed, on_unsubscribed, and DisconnectReasonCode for details.
• The Request / Response pattern is formalized by the addition of the ResponseTopic. Additional properties such as correlation data and be specified via OutgoingMessageProperties and ConnectProperties.
• New subscription features: Shared Subscriptions, Subscription Options, and SubscriptionIdentifier (see subscribe for details).
• Topic Aliases can be sent by both client and server to refer to topic filters by shorter numerical identifiers in order to save bandwidth (see TopicAlias, ServerTopicAliasMax and ClientTopicAliasMax).
• Servers can communicate what features it supports in ConnAckProperties.
• More: message expiration (OutgoingMessageProperties), Receive Maximums and Maximum Packet Sizes (ConnectProperties and ConnAckProperties), and a Will Delay interval (WillProperties) are all supported.

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

clean_session Property

Determines whether a clean session is used once connected.

Syntax

def get_clean_session() -> bool: ...
def set_clean_session(value: bool) -> None: ...

clean_session = property(get_clean_session, set_clean_session)

Default Value

TRUE

Remarks

This property determines whether or not the class should instruct the server to use a clean session when it connects. (Note that this property must be set to the desired value before calling connect.)

By default, clean_session is true, so the server will discard any state data previously associated with the current client_id once the class has connected successfully. In addition, the server will not save any state data when the class disconnects.

Setting clean_session to False before connecting will cause the server to re-associate any previously stored state data for the current client_id. The server will also save any state data that exists when the class is disconnected.

The server-side session state consists of:

• whether a session is present (see SessionPresent),
• client subscriptions (including subscription identifiers in MQTT 5),
• QoS 1 and 2 messages sent to the client pending transmission or completed acknowledgment (and optionally pending QoS 0 messages),
• QoS 2 messages received from the client but not completely acknowledged, and
• the SessionExpInterval (in MQTT 5).

Note that retained messages are not deleted as a result of a session ending, but are not part of the session state.

Client-Side Session State

When setting clean_session to False, it is important that the restore_session method be used to load any previously saved (client-side) session data from a previous session before calling connect. (Successful calls to restore_session will automatically set clean_session to False.)

Similarly, once disconnected, save the string returned by save_session for later use. The saved session information may be used when connecting with clean_session set to False at a later time.

The client-side session state consists of:

• QoS 1 and QoS 2 messages which have been sent to the Server, but have not been completely acknowledged, and
• QoS 2 messages which have been received from the Server, but have not been completely acknowledged.

Refer to save_session and restore_session for more information.

MQTT 5 Notes

In MQTT 5, the "Clean Session" flag from v3.1.1 is split into a "Clean Start" flag indicating that the server should discard previously saved session data from this connection, and a SessionExpInterval controlling the length of time the server should preserve the session data after disconnection.

In MQTT 5, this property acts only as the "Clean Start" flag. It determines whether or not the class should instruct the server to discard any previously stored session data associated with the current client_id and start a new clean session.

For more information on session expiration in MQTT 5, see the SessionExpInterval config. Setting clean_session to True in v3.1.1 is equivalent to setting clean_session to True AND setting SessionExpInterval to 0 in MQTT 5.

As with MQTT 3.1.1, it is important for the client to save and restore its own session data on connection and disconnection depending on the value of clean_session, and to manage its preservation depending on SessionExpInterval.

client_id Property

A string that uniquely identifies this instance of the class to the server.

Syntax

def get_client_id() -> str: ...
def set_client_id(value: str) -> None: ...

client_id = property(get_client_id, set_client_id)

Default Value

""

Remarks

The client_id string is used by the server to uniquely identify each client that is connected to it. In MQTT 5, when the SessionExpInterval config is set to a positive value, the server will also associate it with any session state data that needs to be saved for the length of time specified when the class is disconnected.

If client_id is empty when connect is called, the class's behavior depends on value of clean_session. If clean_session is True, the class will automatically generate a unique value for client_id before connecting. If clean_session is False, the class fails with an error.

connected Property

Triggers a connection or disconnection.

Syntax

def get_connected() -> bool: ...
def set_connected(value: bool) -> None: ...

connected = property(get_connected, set_connected)

Default Value

FALSE

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the class attempt to connect to the host identified by the remote_host property. If successful, after the connection is achieved the value of the property changes to True and the on_connected event is fired.

Setting this property to False closes the connection.

By default the class will connect in plaintext. To enable SSL set ssl_enabled to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with ws:// (plaintext) or wss:// (SSL). For instance, ws://test.mosquitto.org.

When connecting to an MQTT server, the class sends the following information:

• The values of the client_id, clean_session, and keep_alive_interval properties.
• The value of the user property (if non-empty).
• The value of the password property (if non-empty).
• The values of the will_topic and will_message properties and the WillQOS and WillRetain configuration settings.
• MQTT 5 specific values from ClientTopicAliasMax, SessionExpInterval, ConnectProperties and WillProperties.

If clean_session is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to clean_session, save_session, and restore_session for more information about MQTT sessions and session state persistence; refer to will_topic, will_message, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example mqtt1.ClientId = "testClient"; mqtt1.CleanSession = true; mqtt1.KeepAliveInterval = 30; mqtt1.WillTopic = "wills/" + mqtt1.ClientId; mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!"; mqtt1.RemoteHost = "mqtt.test-server.com"; mqtt1.RemotePort = 1883; mqtt1.Connect();

firewall_auto_detect Property

This property tells the class whether or not to automatically detect and use firewall system settings, if available.

Syntax

def get_firewall_auto_detect() -> bool: ...
def set_firewall_auto_detect(value: bool) -> None: ...

firewall_auto_detect = property(get_firewall_auto_detect, set_firewall_auto_detect)

Default Value

FALSE

Remarks

This property tells the class whether or not to automatically detect and use firewall system settings, if available.

firewall_type Property

This property determines the type of firewall to connect through.

Syntax

def get_firewall_type() -> int: ...
def set_firewall_type(value: int) -> None: ...

firewall_type = property(get_firewall_type, set_firewall_type)

Default Value

0

Remarks

This property determines the type of firewall to connect through. The applicable values are as follows:

firewall_host Property

This property contains the name or IP address of firewall (optional).

Syntax

def get_firewall_host() -> str: ...
def set_firewall_host(value: str) -> None: ...

firewall_host = property(get_firewall_host, set_firewall_host)

Default Value

""

Remarks

This property contains the name or IP address of firewall (optional). If a firewall_host is given, the requested connections will be authenticated through the specified firewall when connecting.

If this property is set to a Domain Name, a DNS request is initiated. Upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, the class fails with an error.

firewall_password Property

This property contains a password if authentication is to be used when connecting through the firewall.

Syntax

def get_firewall_password() -> str: ...
def set_firewall_password(value: str) -> None: ...

firewall_password = property(get_firewall_password, set_firewall_password)

Default Value

""

Remarks

This property contains a password if authentication is to be used when connecting through the firewall. If firewall_host is specified, the firewall_user and firewall_password properties are used to connect and authenticate to the given firewall. If the authentication fails, the class fails with an error.

firewall_port Property

This property contains the transmission control protocol (TCP) port for the firewall Host .

Syntax

def get_firewall_port() -> int: ...
def set_firewall_port(value: int) -> None: ...

firewall_port = property(get_firewall_port, set_firewall_port)

Default Value

0

Remarks

This property contains the transmission control protocol (TCP) port for the firewall firewall_host. See the description of the firewall_host property for details.

Note: This property is set automatically when firewall_type is set to a valid value. See the description of the firewall_type property for details.

firewall_user Property

This property contains a user name if authentication is to be used connecting through a firewall.

Syntax

def get_firewall_user() -> str: ...
def set_firewall_user(value: str) -> None: ...

firewall_user = property(get_firewall_user, set_firewall_user)

Default Value

""

Remarks

This property contains a user name if authentication is to be used connecting through a firewall. If the firewall_host is specified, this property and firewall_password properties are used to connect and authenticate to the given firewall. If the authentication fails, the class fails with an error.

incoming_message_count Property

The number of records in the IncomingMessage arrays.

Syntax

def get_incoming_message_count() -> int: ...

incoming_message_count = property(get_incoming_message_count, None)

Default Value

0

Remarks

This property controls the size of the following arrays:

• incoming_message_content_type
• incoming_message_correlation_data
• incoming_message_duplicate
• incoming_message_message
• incoming_message_message_exp_interval
• incoming_message_packet_id
• incoming_message_payload_format_indicator
• incoming_message_qos
• incoming_message_response_topic
• incoming_message_retained
• incoming_message_state
• incoming_message_subscription_identifiers
• incoming_message_topic
• incoming_message_topic_alias

The array indices start at 0 and end at incoming_message_count - 1.

This property is read-only.

incoming_message_content_type Property

String describing the content of the message.

Syntax

def get_incoming_message_content_type(incoming_message_index: int) -> str: ...

Default Value

""

Remarks

String describing the content of the message. Defined by the sending and receiving application.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_correlation_data Property

Used by the sender of the request message to identify which request the response message is for when it is received.

Syntax

def get_incoming_message_correlation_data(incoming_message_index: int) -> str: ...

Default Value

""

Remarks

Used by the sender of the request message to identify which request the response message is for when it is received.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_duplicate Property

Whether or not this message's Duplicate flag is set.

Syntax

def get_incoming_message_duplicate(incoming_message_index: int) -> bool: ...

Default Value

FALSE

Remarks

Whether or not this message's Duplicate flag is set.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_message Property

This message's raw data payload.

Syntax

def get_incoming_message_message(incoming_message_index: int) -> bytes: ...

Default Value

""

Remarks

This message's raw data payload.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_message_exp_interval Property

The lifetime of the message in seconds specified by the sender.

Syntax

def get_incoming_message_message_exp_interval(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

The lifetime of the message in seconds specified by the sender.

For outgoing messages, the value is useful for instructing the server to delete its copies of the message for any subscribers it has not been able to start delivery to.

For incoming messages, the value sent by the server is the lifetime specified by the sender minus the time the message has been waiting in the server.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_packet_id Property

This message's packet Id.

Syntax

def get_incoming_message_packet_id(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

This message's packet Id.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_payload_format_indicator Property

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data.

Syntax

def get_incoming_message_payload_format_indicator(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. Possible values are:

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_qos Property

This message's QoS level.

Syntax

def get_incoming_message_qos(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

This message's QoS level. Possible values are:

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_response_topic Property

String used as the topic name for a response message.

Syntax

def get_incoming_message_response_topic(incoming_message_index: int) -> str: ...

Default Value

""

Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_retained Property

Whether or not this message's Retain flag is set.

Syntax

def get_incoming_message_retained(incoming_message_index: int) -> bool: ...

Default Value

FALSE

Remarks

Whether or not this message's Retain flag is set.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_state Property

This message's current state.

Syntax

def get_incoming_message_state(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

This message's current state.

Possible Outgoing Message States:

Possible Incoming Message States:

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_subscription_identifiers Property

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

Syntax

def get_incoming_message_subscription_identifiers(incoming_message_index: int) -> str: ...

Default Value

""

Remarks

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

This property is only applicable to incoming messages.

If SubscriptionIdentifier is set when subscribing, it will be included in any messages delivered by the broker for the topics specified in that packet.

See the subscribe method for more details.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_topic Property

This message's topic.

Syntax

def get_incoming_message_topic(incoming_message_index: int) -> str: ...

Default Value

""

Remarks

This message's topic.

MQTT 5 Notes:

If this value is empty, the incoming_message_topic_alias property holds the assigned alias for the topic.

If this value is not empty and incoming_message_topic_alias is non-zero,

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

incoming_message_topic_alias Property

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

Syntax

def get_incoming_message_topic_alias(incoming_message_index: int) -> int: ...

Default Value

0

Remarks

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the incoming_message_topic string is empty.

For details on setting topic aliases for outgoing messages, see the TopicAlias configuration setting.

Valid only for MQTT 5.

The incoming_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the incoming_message_count property.

This property is read-only.

keep_alive_interval Property

The maximum period of inactivity the class will allow before sending a keep-alive packet.

Syntax

def get_keep_alive_interval() -> int: ...
def set_keep_alive_interval(value: int) -> None: ...

keep_alive_interval = property(get_keep_alive_interval, set_keep_alive_interval)

Default Value

0

Remarks

The keep_alive_interval, if set to a non-zero value, is the maximum number of seconds that the class will allow the connection to be idle before sending a PINGREQ (ping request) packet to the server. The value of keep_alive_interval is sent to the server when connect is called; it cannot be changed when the class is already connected.

MQTT servers are required to measure periods of inactivity for all clients who specify a non-zero keep_alive_interval, and must disconnect them if they have not communicated within 1.5 times keep_alive_interval.

Similarly, if the class doesn't receive a PINGRESP (ping response) packet within keep_alive_interval seconds after sending a PINGREQ packet, it will disconnect from the server.

If keep_alive_interval is set to 0 (default), keep-alive functionality is disabled entirely. In this case, the class will not send any PINGREQ packets, and the server is not required to close the connection due to inactivity.

Note that, regardless of keep-alive settings, the server is always free to disconnect clients it deems "unresponsive".

local_host Property

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

def get_local_host() -> str: ...
def set_local_host(value: str) -> None: ...

local_host = property(get_local_host, set_local_host)

Default Value

""

Remarks

The local_host property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the class initiate connections (or accept in the case of server classs) only through that interface.

If the class is connected, the local_host property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multi-homed hosts (machines with more than one IP interface).

NOTE: local_host is not persistent. You must always set it in code, and never in the property window.

local_port Property

The TCP port in the local host where the class binds.

Syntax

def get_local_port() -> int: ...
def set_local_port(value: int) -> None: ...

local_port = property(get_local_port, set_local_port)

Default Value

0

Remarks

This property must be set before a connection is attempted. It instructs the class to bind to a specific port (or communication endpoint) in the local machine.

Setting this property to 0 (default) enables the system to choose an open port at random. The chosen port will be returned by the local_port property after the connection is established.

local_port cannot be changed once a connection is made. Any attempt to set this property when a connection is active will generate an error.

This property is useful when trying to connect to services that require a trusted port in the client side.

outgoing_message_count Property

The number of records in the OutgoingMessage arrays.

Syntax

def get_outgoing_message_count() -> int: ...

outgoing_message_count = property(get_outgoing_message_count, None)

Default Value

0

Remarks

This property controls the size of the following arrays:

• outgoing_message_content_type
• outgoing_message_correlation_data
• outgoing_message_duplicate
• outgoing_message_message
• outgoing_message_message_exp_interval
• outgoing_message_packet_id
• outgoing_message_payload_format_indicator
• outgoing_message_qos
• outgoing_message_response_topic
• outgoing_message_retained
• outgoing_message_state
• outgoing_message_subscription_identifiers
• outgoing_message_topic
• outgoing_message_topic_alias

The array indices start at 0 and end at outgoing_message_count - 1.

This property is read-only.

outgoing_message_content_type Property

String describing the content of the message.

Syntax

def get_outgoing_message_content_type(outgoing_message_index: int) -> str: ...

Default Value

""

Remarks

String describing the content of the message. Defined by the sending and receiving application.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_correlation_data Property

Used by the sender of the request message to identify which request the response message is for when it is received.

Syntax

def get_outgoing_message_correlation_data(outgoing_message_index: int) -> str: ...

Default Value

""

Remarks

Used by the sender of the request message to identify which request the response message is for when it is received.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_duplicate Property

Whether or not this message's Duplicate flag is set.

Syntax

def get_outgoing_message_duplicate(outgoing_message_index: int) -> bool: ...

Default Value

FALSE

Remarks

Whether or not this message's Duplicate flag is set.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_message Property

This message's raw data payload.

Syntax

def get_outgoing_message_message(outgoing_message_index: int) -> bytes: ...

Default Value

""

Remarks

This message's raw data payload.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_message_exp_interval Property

The lifetime of the message in seconds specified by the sender.

Syntax

def get_outgoing_message_message_exp_interval(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

The lifetime of the message in seconds specified by the sender.

For outgoing messages, the value is useful for instructing the server to delete its copies of the message for any subscribers it has not been able to start delivery to.

For incoming messages, the value sent by the server is the lifetime specified by the sender minus the time the message has been waiting in the server.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_packet_id Property

This message's packet Id.

Syntax

def get_outgoing_message_packet_id(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

This message's packet Id.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_payload_format_indicator Property

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data.

Syntax

def get_outgoing_message_payload_format_indicator(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

Indicates whether the payload is unspecified bytes or UTF-8 Encoded character data. Possible values are:

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_qos Property

This message's QoS level.

Syntax

def get_outgoing_message_qos(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

This message's QoS level. Possible values are:

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_response_topic Property

String used as the topic name for a response message.

Syntax

def get_outgoing_message_response_topic(outgoing_message_index: int) -> str: ...

Default Value

""

Remarks

String used as the topic name for a response message.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_retained Property

Whether or not this message's Retain flag is set.

Syntax

def get_outgoing_message_retained(outgoing_message_index: int) -> bool: ...

Default Value

FALSE

Remarks

Whether or not this message's Retain flag is set.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_state Property

This message's current state.

Syntax

def get_outgoing_message_state(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

This message's current state.

Possible Outgoing Message States:

Possible Incoming Message States:

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_subscription_identifiers Property

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

Syntax

def get_outgoing_message_subscription_identifiers(outgoing_message_index: int) -> str: ...

Default Value

""

Remarks

A comma separated list of any SubscriptionIdentifiers associated with any client subscription(s) that caused this message to be delivered.

This property is only applicable to incoming messages.

If SubscriptionIdentifier is set when subscribing, it will be included in any messages delivered by the broker for the topics specified in that packet.

See the subscribe method for more details.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_topic Property

This message's topic.

Syntax

def get_outgoing_message_topic(outgoing_message_index: int) -> str: ...

Default Value

""

Remarks

This message's topic.

MQTT 5 Notes:

If this value is empty, the outgoing_message_topic_alias property holds the assigned alias for the topic.

If this value is not empty and outgoing_message_topic_alias is non-zero,

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

outgoing_message_topic_alias Property

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

Syntax

def get_outgoing_message_topic_alias(outgoing_message_index: int) -> int: ...

Default Value

0

Remarks

An integer used to identify the topic instead of the full topic filter in order to reduce the size of the publish packet.

If a non-zero topic alias is received, the client should establish a new topic alias mapping or use an existing mapping, depending on whether the outgoing_message_topic string is empty.

For details on setting topic aliases for outgoing messages, see the TopicAlias configuration setting.

Valid only for MQTT 5.

The outgoing_message_index parameter specifies the index of the item in the array. The size of the array is controlled by the outgoing_message_count property.

This property is read-only.

password Property

A password if authentication is to be used.

Syntax

def get_password() -> str: ...
def set_password(value: str) -> None: ...

password = property(get_password, set_password)

Default Value

""

Remarks

This property can be set to a password if authentication is to be used.

In MQTT 3.1.1, while a user may be specified without a password, setting a password without a user is not supported; attempting to do so will cause the server to reject the connection attempt.

In MQTT 5, a password may be set without a user, allowing the field to be used for credentials other than a password.

ready_to_send Property

Indicates whether the class is ready to send data.

Syntax

def get_ready_to_send() -> bool: ...

ready_to_send = property(get_ready_to_send, None)

Default Value

FALSE

Remarks

This property indicates that the underlying TCP/IP subsystem is ready to accept data. This is True after connecting to the remote host, and will become False if a call to publish_data or publish_message fails due to a WOULDBLOCK condition.

Once data can be sent again, the on_ready_to_send event will fire and this property will be True.

If a WOULDBLOCK error occurs while sending a message the class will automatically complete the transmission when sending is possible. No action needs to be taken to re-send the message. on_ready_to_send will fire after the class completes any partially sent messages.

This property is read-only.

remote_host Property

The address of the remote host. Domain names are resolved to IP addresses.

Syntax

def get_remote_host() -> str: ...
def set_remote_host(value: str) -> None: ...

remote_host = property(get_remote_host, set_remote_host)

Default Value

""

Remarks

This property specifies the IP address (IP number in dotted internet format) or Domain Name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If this property is set to a Domain Name, a DNS request is initiated, and upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, an error is returned.

If the class is configured to use a SOCKS firewall, the value assigned to this property may be preceded with an "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

By default the class will connect in plaintext. To enable SSL set ssl_enabled to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with ws:// (plaintext) or wss:// (SSL). For instance, ws://test.mosquitto.org.

remote_port Property

The port of the MQTT server (default is 1883). The default port for SSL is 8883.

Syntax

def get_remote_port() -> int: ...
def set_remote_port(value: int) -> None: ...

remote_port = property(get_remote_port, set_remote_port)

Default Value

1883

Remarks

This property specifies a service port on the remote host to connect to.

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

ssl_accept_server_cert_encoded Property

This is the certificate (PEM/Base64 encoded).

Syntax

def get_ssl_accept_server_cert_encoded() -> bytes: ...
def set_ssl_accept_server_cert_encoded(value: bytes) -> None: ...

ssl_accept_server_cert_encoded = property(get_ssl_accept_server_cert_encoded, set_ssl_accept_server_cert_encoded)

Default Value

""

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The ssl_accept_server_cert_store and ssl_accept_server_cert_subject properties also may be used to specify a certificate.

When ssl_accept_server_cert_encoded is set, a search is initiated in the current ssl_accept_server_cert_store for the private key of the certificate. If the key is found, ssl_accept_server_cert_subject is updated to reflect the full subject of the selected certificate; otherwise, ssl_accept_server_cert_subject is set to an empty string.

ssl_cert_encoded Property

This is the certificate (PEM/Base64 encoded).

Syntax

def get_ssl_cert_encoded() -> bytes: ...
def set_ssl_cert_encoded(value: bytes) -> None: ...

ssl_cert_encoded = property(get_ssl_cert_encoded, set_ssl_cert_encoded)

Default Value

""

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The ssl_cert_store and ssl_cert_subject properties also may be used to specify a certificate.

When ssl_cert_encoded is set, a search is initiated in the current ssl_cert_store for the private key of the certificate. If the key is found, ssl_cert_subject is updated to reflect the full subject of the selected certificate; otherwise, ssl_cert_subject is set to an empty string.

ssl_cert_store Property

This is the name of the certificate store for the client certificate.

Syntax

def get_ssl_cert_store() -> bytes: ...
def set_ssl_cert_store(value: bytes) -> None: ...

ssl_cert_store = property(get_ssl_cert_store, set_ssl_cert_store)

Default Value

"MY"

Remarks

This is the name of the certificate store for the client certificate.

The ssl_cert_store_type property denotes the type of the certificate store specified by ssl_cert_store. If the store is password protected, specify the password in ssl_cert_store_password.

ssl_cert_store is used in conjunction with the ssl_cert_subject property to specify client certificates. If ssl_cert_store has a value, and ssl_cert_subject or ssl_cert_encoded is set, a search for a certificate is initiated. Please see the ssl_cert_subject property for details.

Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

When the certificate store type is PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

ssl_cert_store_password Property

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

Syntax

def get_ssl_cert_store_password() -> str: ...
def set_ssl_cert_store_password(value: str) -> None: ...

ssl_cert_store_password = property(get_ssl_cert_store_password, set_ssl_cert_store_password)

Default Value

""

Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

ssl_cert_store_type Property

This is the type of certificate store for this certificate.

Syntax

def get_ssl_cert_store_type() -> int: ...
def set_ssl_cert_store_type(value: int) -> None: ...

ssl_cert_store_type = property(get_ssl_cert_store_type, set_ssl_cert_store_type)

Default Value

0

Remarks

This is the type of certificate store for this certificate.

The class supports both public and private keys in a variety of formats. When the cstAuto value is used, the class will automatically determine the type. This property can take one of the following values:

ssl_cert_subject Property

This is the subject of the certificate used for client authentication.

Syntax

def get_ssl_cert_subject() -> str: ...
def set_ssl_cert_subject(value: str) -> None: ...

ssl_cert_subject = property(get_ssl_cert_subject, set_ssl_cert_subject)

Default Value

""

Remarks

This is the subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=support@nsoftware.com". Common fields and their meanings are as follows:

If a field value contains a comma, it must be quoted.

ssl_enabled Property

Whether TLS/SSL is enabled.

Syntax

def get_ssl_enabled() -> bool: ...
def set_ssl_enabled(value: bool) -> None: ...

ssl_enabled = property(get_ssl_enabled, set_ssl_enabled)

Default Value

FALSE

Remarks

This setting specifies whether TLS/SSL is enabled in the class. When False (default) the class operates in plaintext mode. When True TLS/SSL is enabled.

TLS/SSL may also be enabled by setting ssl_start_mode. Setting ssl_start_mode will automatically update this property value.

ssl_provider Property

This specifies the SSL/TLS implementation to use.

Syntax

def get_ssl_provider() -> int: ...
def set_ssl_provider(value: int) -> None: ...

ssl_provider = property(get_ssl_provider, set_ssl_provider)

Default Value

0

Remarks

This property specifies the SSL/TLS implementation to use. In most cases the default value of 0 (Automatic) is recommended and should not be changed. When set to 0 (Automatic) the class will select whether to use the platform implementation or the internal implementation depending on the operating system as well as the TLS version being used.

Possible values are:

In most cases using the default value (Automatic) is recommended. The class will select a provider depending on the current platform.

When Automatic is selected, on Windows the class will use the platform implementation. On Linux/macOS the class will use the internal implementation. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used on all platforms.

ssl_server_cert_encoded Property

This is the certificate (PEM/Base64 encoded).

Syntax

def get_ssl_server_cert_encoded() -> bytes: ...

ssl_server_cert_encoded = property(get_ssl_server_cert_encoded, None)

Default Value

""

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The ssl_server_cert_store and ssl_server_cert_subject properties also may be used to specify a certificate.

When ssl_server_cert_encoded is set, a search is initiated in the current ssl_server_cert_store for the private key of the certificate. If the key is found, ssl_server_cert_subject is updated to reflect the full subject of the selected certificate; otherwise, ssl_server_cert_subject is set to an empty string.

This property is read-only.

timeout Property

A timeout for the class.

Syntax

def get_timeout() -> int: ...
def set_timeout(value: int) -> None: ...

timeout = property(get_timeout, set_timeout)

Default Value

60

Remarks

If the timeout property is set to 0, all operations return immediately, potentially failing with a WOULDBLOCK error if data cannot be sent immediately.

If timeout is set to a positive value, data is sent in a blocking manner and the class will wait for the operation to complete before returning control. The class will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of timeout seconds.

The class will use do_events to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If timeout expires, and the operation is not yet complete, the class fails with an error.

Please note that by default, all timeouts are inactivity timeouts, i.e. the timeout period is extended by timeout seconds when any amount of data is successfully sent or received.

The default value for the timeout property is 60 seconds.

user Property

A username if authentication is to be used.

Syntax

def get_user() -> str: ...
def set_user(value: str) -> None: ...

user = property(get_user, set_user)

Default Value

""

Remarks

This property can be set to a username if authentication is to be used.

In MQTT 3.1.1, while a user may be specified without a password, setting a password without a user is not supported; attempting to do so will cause the server to reject the connection attempt.

In MQTT 5, a password may be set without a user, allowing the field to be used for credentials other than a password.

version Property

The MQTT protocol version that the class will conform to.

Syntax

def get_version() -> int: ...
def set_version(value: int) -> None: ...

version = property(get_version, set_version)

Default Value

0

Remarks

This property specifies the version of the MQTT protocol to use. Possible values are:

will_message Property

The message that the server should publish in the event of an ungraceful disconnection.

Syntax

def get_will_message() -> str: ...
def set_will_message(value: str) -> None: ...

will_message = property(get_will_message, set_will_message)

Default Value

""

Remarks

This property may be set before calling connect to specify to the server a message that should be published on will_topic if the connection is closed ungracefully. Since it is sent to the server when connect is called, this property's value cannot be changed when already connected.

Note that the will_message will only be sent to the server when connect is called if will_topic is set.

Refer to will_topic for more information about MQTT Will functionality.

will_topic Property

The topic that the server should publish the WillMessage to in the event of an ungraceful disconnection.

Syntax

def get_will_topic() -> str: ...
def set_will_topic(value: str) -> None: ...

will_topic = property(get_will_topic, set_will_topic)

Default Value

""

Remarks

This property may be set before calling connect to specify the topic name that the server should publish the will_message on if the connection is closed ungracefully. Since it is sent to the server when connect is called, this property's value cannot be changed when already connected.

MQTT Wills

The Will feature of MQTT allows a client to specify to the server a will_message to publish (as well as a will_topic to publish it on) in the event of an ungraceful disconnection.

An "ungraceful disconnection" is any disconnection other than one triggered by calling disconnect (in which case the server discards the Will message without publishing it). Note that in MQTT 5, the client can set a DisconnectReasonCode of 0x04 before calling disconnect to instruct the server to publish the Will message anyway.

In addition to the will_topic and will_message properties, the WillQOS setting may be used to specify the Will message's QoS level, and the WillRetain setting to set the Will message's Retain flag. Refer to those settings for more information.

If will_topic is set to empty string (default) when connect is called, the class will not send a Will to the server.

In MQTT 5, the "WillDelayInterval" value in the WillProperties config can specify a delay between the ending of the connection and sending the will message, so that the will_message will not be sent if a connection is re-established within a certain period of time.

config Method

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

Remarks

config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

connect Method

Connects to the remote host.

Syntax

def connect() -> None: ...

Remarks

This method connects to the remote host specified by remote_host and remote_port. Calling this method is equivalent to setting the connected property to True.

By default the class will connect in plaintext. To enable SSL set ssl_enabled to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with ws:// (plaintext) or wss:// (SSL). For instance, ws://test.mosquitto.org.

When connecting to an MQTT server, the class sends the following information:

• The values of the client_id, clean_session, and keep_alive_interval properties.
• The value of the user property (if non-empty).
• The value of the password property (if non-empty).
• The values of the will_topic and will_message properties and the WillQOS and WillRetain configuration settings.
• MQTT 5 specific values from ClientTopicAliasMax, SessionExpInterval, ConnectProperties and WillProperties.

If clean_session is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to clean_session, save_session, and restore_session for more information about MQTT sessions and session state persistence; refer to will_topic, will_message, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example mqtt1.ClientId = "testClient"; mqtt1.CleanSession = true; mqtt1.KeepAliveInterval = 30; mqtt1.WillTopic = "wills/" + mqtt1.ClientId; mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!"; mqtt1.RemoteHost = "mqtt.test-server.com"; mqtt1.RemotePort = 1883; mqtt1.Connect();

connect_to Method

Connects to the remote host.

Syntax

def connect_to(host: str, port: int) -> None: ...

Remarks

This method connects to the remote host specified by the Host and Port parameters. Calling this method is equivalent to setting the remote_host property to Host, setting remote_port to Port, and then setting the connected property to True.

By default the class will connect in plaintext. To enable SSL set ssl_enabled to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with ws:// (plaintext) or wss:// (SSL). For instance, ws://test.mosquitto.org.

When connecting to an MQTT server, the class sends the following information:

• The values of the client_id, clean_session, and keep_alive_interval properties.
• The value of the user property (if non-empty).
• The value of the password property (if non-empty).
• The values of the will_topic and will_message properties and the WillQOS and WillRetain configuration settings.
• MQTT 5 specific values from ClientTopicAliasMax, SessionExpInterval, ConnectProperties and WillProperties.

If clean_session is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to clean_session, save_session, and restore_session for more information about MQTT sessions and session state persistence; refer to will_topic, will_message, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example mqtt1.ClientId = "testClient"; mqtt1.CleanSession = true; mqtt1.KeepAliveInterval = 30; mqtt1.WillTopic = "wills/" + mqtt1.ClientId; mqtt1.WillMessage = mqtt1.ClientId + " was disconnected ungracefully!"; mqtt1.ConnectTo("mqtt.test-server.com", 1883);

disconnect Method

This method disconnects from the remote host.

Syntax

def disconnect() -> None: ...

Remarks

This method disconnects from the remote host. Calling this method is equivalent to setting the connected property to False.

Refer to the connected property for more information about MQTT-specific behavior.

do_events Method

Processes events from the internal message queue.

Syntax

def do_events() -> None: ...

Remarks

When do_events is called, the class processes any available events. If no events are available, it waits for a preset period of time, and then returns.

interrupt Method

Interrupt the current action and disconnects from the remote host.

Syntax

def interrupt() -> None: ...

Remarks

This method will interrupt the current method (if applicable) and cause the class to disconnect from the remote host.

publish_data Method

Publishes a message with a raw data payload.

Syntax

def publish_data(topic: str, qos: int, data: bytes) -> None: ...

Remarks

This method publishes an MQTT message with a raw data payload to the specified Topic at a given QOS level.

Publish Examples // Publish a simple string-based message. mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!"); // Publish a raw data message. byte[] catPicture = ...; mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);

The Retain configuration setting may be set before calling this method in order to publish a retained message (see Retain for more information).

Topic Names

Topic names are case-sensitive, must be 1-65535 characters long, and may include any characters except wildcard characters (# and +) and the null character. The / character separates levels within a topic name, which is important in the context of subscribing (see subscribe for more information).

Keep in mind that using topic names with leading or trailing / characters will cause topic levels with zero-length names to be created. That is, a topic name like /a/b/ consists of the levels '', 'a', 'b', and ''. Depending on the server, multiple successive /s may also cause zero-length levels to be created, or may be treated as a single /.

Topic names that begin with a $ are "system topics", and servers will typically prevent clients from publishing to them.

For example, topic names that begin with $share are reserved for Shared Subscriptions (see subscribe).

QoS Values

QoS values set the service level for delivery of a message. Values range from 0 to 2 and have the following meanings:

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBACK (publish acknowledgment) packet.
3. The on_message_ack event is fired.
4. The message is removed from OutgoingMessage*.
5. The on_message_out event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBREC (publish received) packet.
3. The class sends a PUBREL (publish release) packet in response.
4. The class waits to receive a PUBCOMP (publish complete) packet.
5. The on_message_ack event is fired.
6. The message is removed from OutgoingMessage*.
7. The on_message_out event is fired.

In MQTT 3.1.1, the RepublishInterval configuration setting, if set to a non-zero value (default), controls how long the class will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

MQTT 5 Notes

MQTT 5 makes a number of new features available when publishing messages, including:

• TopicAlias - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if TopicAlias is set the Topic parameter does not need to be set. This reduces the size of the message sent to the server.
• Request / Response - Set a ResponseTopic which identifies the topic to which a receiver should respond.

Some of these features require configuration settings to be set prior to publishing. In these cases, note that these configuration settings will continue to be applicable to any future PUBLISH packets sent with the method unless they are updated or reset. To prevent clear a previously set configuration setting, set it to "", or -1 (for integers).

See the OutgoingMessageProperties configuration setting for additional details.

publish_message Method

Publishes a message with a string payload.

Syntax

def publish_message(topic: str, qos: int, message: str) -> None: ...

Remarks

This method publishes an MQTT message with a string payload to the specified Topic at a given QOS level.

Publish Examples // Publish a simple string-based message. mqtt1.PublishMessage("/home/floor1/security/camera2", 1, "Cat detected!"); // Publish a raw data message. byte[] catPicture = ...; mqtt1.PublishData("/home/floor1/security/camera2", 1, catPicture);

The Retain configuration setting may be set before calling this method in order to publish a retained message (see Retain for more information).

Topic Names

Topic names are case-sensitive, must be 1-65535 characters long, and may include any characters except wildcard characters (# and +) and the null character. The / character separates levels within a topic name, which is important in the context of subscribing (see subscribe for more information).

Keep in mind that using topic names with leading or trailing / characters will cause topic levels with zero-length names to be created. That is, a topic name like /a/b/ consists of the levels '', 'a', 'b', and ''. Depending on the server, multiple successive /s may also cause zero-length levels to be created, or may be treated as a single /.

Topic names that begin with a $ are "system topics", and servers will typically prevent clients from publishing to them.

For example, topic names that begin with $share are reserved for Shared Subscriptions (see subscribe).

QoS Values

QoS values set the service level for delivery of a message. Values range from 0 to 2 and have the following meanings:

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBACK (publish acknowledgment) packet.
3. The on_message_ack event is fired.
4. The message is removed from OutgoingMessage*.
5. The on_message_out event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBREC (publish received) packet.
3. The class sends a PUBREL (publish release) packet in response.
4. The class waits to receive a PUBCOMP (publish complete) packet.
5. The on_message_ack event is fired.
6. The message is removed from OutgoingMessage*.
7. The on_message_out event is fired.

In MQTT 3.1.1, the RepublishInterval configuration setting, if set to a non-zero value (default), controls how long the class will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

MQTT 5 Notes

MQTT 5 makes a number of new features available when publishing messages, including:

• TopicAlias - Set an integer alias along with the topic name when first publishing a message. When publishing additional messages to the same topic if TopicAlias is set the Topic parameter does not need to be set. This reduces the size of the message sent to the server.
• Request / Response - Set a ResponseTopic which identifies the topic to which a receiver should respond.

Some of these features require configuration settings to be set prior to publishing. In these cases, note that these configuration settings will continue to be applicable to any future PUBLISH packets sent with the method unless they are updated or reset. To prevent clear a previously set configuration setting, set it to "", or -1 (for integers).

See the OutgoingMessageProperties configuration setting for additional details.

reset Method

Reset the class.

Syntax

def reset() -> None: ...

Remarks

This method will reset the class's properties to their default values.

restore_session Method

Restores session state data.

Syntax

def restore_session(state_data: str) -> None: ...

Remarks

This method restores previously-saved session state data and sets clean_session to False. If the SessionStateFile configuration setting is set, the class will use the contents of that file to restore the session state data, ignoring the string passed to this method.

Depending on the elapsed time between connections the server may discard any previously saved session data on its side.

In MQTT 3.1.1, the time after which the server discards saved session data is not defined in the protocol specification and may vary between implementations. As a result, when re-connecting it may not be known if the server is capable of restoring a previous session.

To determine if a session can be restored on connection, set clean_session to False, client_id to the same value used in the initial connection, and call connect_to.

When the on_connected event fires, query the SessionPresent configuration setting. If SessionPresent is True the session should be restored by calling restore_session. If SessionPresent is False the session should not be restored so that the connection proceeds as a clean session.

Note: Not all servers support the use of SessionPresent.

Restore Session Example (Query SessionPresent) mqtt1.CleanSession = false; mqtt1.ClientId = clientId; mqtt1.OnConnected += (s, e) => { if (mqtt1.Config("SessionPresent").ToLower() == "true") mqtt1.RestoreSession(sessionStr); }; mqtt1.ConnectTo(host,port);

If it is known that the server has not discarded the session state, for instance from familiarity with the server implementation and its behavior, then a simplified procedure can be performed. Simply set client_id to the value used in the initial connection, call restore_session, and then call connect_to.

Restore Session Example (Server Status Known) mqtt1.ClientId = clientId; mqtt1.RestoreSession(sessionStr); mqtt1.ConnectTo(host,port);

Refer to clean_session and save_session for more information.

MQTT 5 Notes

In MQTT 5, the time after which the server discards saved session data is controlled by the SessionExpInterval. The server is required to store state data for the amount of time specified by this value, at which point it is required to delete it.

This feature allows the client to use its own time-based logic to determine whether it is necessary to call restore_session.

save_session Method

Saves session state data.

Syntax

def save_session() -> str: ...

Remarks

This method saves session state data currently held by the class, returning it as a string that can later be used to restore it. If the SessionStateFile configuration setting is set, the class will also write the session state data to that file (creating and/or overwriting it, as necessary).

Refer to clean_session and restore_session for more information.

subscribe Method

Subscribes the class to one or more topic filters.

Syntax

def subscribe(topic_filter: str, qos: int) -> None: ...

Remarks

This method subscribes the class to one or more topic filters using one or more QoS levels.

The on_subscribed event will fire once for each topic filter given once the server acknowledges the subscription request(s). Keep in mind that the server is allowed to start publishing messages before it sends the acknowledgment.

It is legal to call subscribe again for the same topic filter at any time, and pass a different QoS value at that time if desired. The on_subscribed event will fire as normal when doing this.

Subscribe Examples // Subscribed event handler. mqtt1.OnSubscribed += (s, e) => { if (e.ResponseCode <= 2) Console.WriteLine("Subscribed to " + e.TopicFilter + " at QoS " + e.QOS + "."); else Console.WriteLine("Failed to subscribe to " + e.TopicFilter + "."); }; // Basic, subscribe to some topic filters, all at the same QoS level. mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 2); // A bit more advanced, subscribe to the same topic filters, but at different QoS levels. mqtt1.Config("TopicQOSArray=1,2,2"); // The 0 is ignored here since we've specified individual QoS values explicitly. mqtt1.Subscribe("home,home/floor1/+/temperature,home/floor2/#", 0);

Topic Filters

The string passed for TopicFilter must contain one or more valid topic filter strings, separated by the delimiter string specified by the TopicDelimiter configuration setting (, by default).

A topic filter is a case-sensitive string between 1 and 65535 characters long (per topic filter), and can include any character other than the null character. Certain characters have special meanings:

• / - The topic level separator
• # - The multi-level wildcard (zero or more levels)
• + - The single-level wildcard (exactly one level)
• Leading $ - Denotes a "system topic"

Note that both types of wildcards may be used in the same topic filter.

Topic Level Separators

The topic level separator, as its name implies, is used to separate a topic name (or in this case, filter) into "levels". This concept of topic names having levels is what allows topic filters to match multiple topics through the use of wildcards. For the examples in the next sections, assume the following topics exist:

• home/floor1
• home/floor1/livingRoom
• home/floor1/livingRoom/temperature
• home/floor1/kitchen/temperature
• home/floor1/kitchen/fridge/temperature
• home/floor2/bedroom1
• home/floor2/bedroom1/temperature

Multi-level Wildcards

The multi-level wildcard character is used at the end of a topic filter to make it match an arbitrary number of successive levels. For example, the topic filter home/floor1/# would match the following topics:

• home/floor1 (because it can match zero levels)
• home/floor1/livingRoom
• home/floor1/livingRoom/temperature
• home/floor1/kitchen/temperature
• home/floor1/kitchen/fridge/temperature

Here are some things to keep in mind when using a multi-level wildcard:

• # must always be the last character in the topic filter (e.g., home/floor1/#/livingRoom is not valid)
• # must always be preceded by a / (e.g., home/floor1# is not valid)
• # by itself is a valid topic filter, and will match all topics except system topics

Single-level Wildcards

The single-level wildcard character is used between two /s in a topic filter to make it any single level. For example, the topic filter home/floor1/+/temperature would match the following topics:

• home/floor1/livingRoom/temperature
• home/floor1/kitchen/temperature

Any number of single-level wildcards are supported in a topic filter. For example, the topic filter home/+/+/temperature would match the following topics:

• home/floor1/livingRoom/temperature
• home/floor1/kitchen/temperature
• home/floor2/bedroom1/temperature

Here are some things to keep in mind when using single-level wildcards:

• + must always be separated from other levels using /s (e.g., home/floor1+ is invalid, but +/floor1/+ is valid)
• + by itself is a valid topic filter, and will match all topics with exactly one level in their name except system topics
• Remember, topic names with a leading / have a zero-length string as their first level. So a topic named /people would be matched by the topic filter +/+, but not by +
• + must match exactly one level. So for example, the topic filter home/floor1/kitchen/+/temperature would match /home/floor1/kitchen/fridge/temperature, but not home/floor1/kitchen/temperature

System Topics

Topic names which begin with a $ are "system topics". Typically, the server prohibits clients from publishing to such topics, but permits subscribing to them. As described above, wildcards will never match the first level of a topic if it begins with a $.

Note that MQTT 5 defines shared subscriptions, a special type of system topic. See the MQTT 5 notes below for more.

Requested QoS Values

The QoS value passed for QOS will be used to subscribe to all given topic filters, unless the TopicQOSArray configuration setting is used to specify explicit QoS values for each individual topic filter.

QoS values range from 0 to 2 and have the following meanings:

QoS is not guaranteed to be end-to-end in MQTT. The server must downgrade a message's QoS level when delivering it to clients who specified a lower "maximum acceptable" QoS when they subscribed. For example, if Client X subscribes to a topic at QoS 1, and Client Y publishes a message to that topic at QoS 2, the server will downgrade the message to QoS 1 when attempting to deliver it to Client X.

MQTT 5 Notes

MQTT 5 defines several new features that apply to subscriptions, including Shared Subscriptions, Subscription Options and Subscription Identifiers. Some of these features require configuration settings to be set prior to calling subscribe. In these cases, note that thee configuration settings will continue to be applied to any future SUBSCRIBE packets sent with the method unless they are updated or reset. To prevent a value from being included in packets after it has been set previously, set it to "", or -1 (for integers).

Shared Subscriptions

Shared subscriptions allow a client to subscribe to a topic as a part of a group of clients, where each client in the group is subscribing to the same topic. Each message published to such a group will be delivered to only one client in the group, making shared subscriptions useful when several clients share the processing of the publications in parallel.

Subscribing to a topic as part of a shared subscription is similar to a normal subscription, the only difference being the syntax of the topic filter passed to the subscribe method.

The format of this filter is $share/{ShareName}/{filter}, where

• $share is a string literal identifying the subscription as a shared subscriptions.
• {ShareName} is a string at least one character long that must not include /, + or #.
• {filter} is a full topic filter formatted just as in a non-shared subscription.

Unsubscribing is done by passing the same value to the unsubscribe method.

A shared subscription behaves the same way as a non-shared subscription, except that the $share/{ShareName} portion of the topic filter is ignored when filtering publication topics, and that the server will distribute delivery of messages amongst the group, with each message delivered to only one client per group per topic.

Shared subscriptions can be implemented without any additional properties or methods, simply by using the subscribe and unsubscribe methods. However, if it is necessary to verify that the feature is supported by the server, check the "SharedSubscriptionAvailable" value of the ConnAckProperties config.

Shared Subscription Example mqtt1.Subscribe("$share/myShareGroup/myTopicFilter/subTopic", 2);

Subscription Options

MQTT 5 defines three subscription options which can be configured on a per-subscription basis and are useful for message bridge applications:

• No Local flag - indicates that messages must not be forwarded to a connection with a client_id equal to the client_id of the publishing connection (cannot be set on a shared subscription).
• Retain As Published flag - indicates that messages forwarded using this subscription keep the retain flag they were published with (as opposed to always being set to False).
• Retain Handling option - specifies whether retained messages are sent when the subscription is established. Possible values are:

  0	Send retained messages at the time of the subscribe
  1	Send retained messages at subscribe only if the subscription does not currently exist
  2	Do not send retained messages at the time of the subscribe

To specify these options in the subscribe method, the class has three corresponding configuration settings (TopicNLArray, TopicRAPArray and TopicRHArray) which each take a string value in the form of a comma-separated list. Each element in the list corresponds to a topic filter passed to the subscribe method, as with TopicQOSArray.

If the subscription is only for one topic, these lists would have only one value. If the number of elements in the string is less than the number of topic filters in the subscription, the final element will be applied to all remaining topics.

Subscription Options Example mqtt1.Connected = true; mqtt1.Config("TopicNLArray=true, false, true"); // TestTopic1 = true, TestTopic2 = false, TestTopic3 = true mqtt1.Config("TopicRAPArray=false"); // TestTopic1 = false, TestTopic2 = false, TestTopic3 = false mqtt1.Config("TopicRHArray=1, 0"); // // TestTopic1 = 1, TestTopic2 = 0, TestTopic3 = 0 mqtt1.Subscribe("TestTopic1, TestTopic2, TestTopic3", 1);

Subscription Identifiers

MQTT 5 allows clients to specify a numeric subscription identifier which will be returned with messages delivered for that subscription.

To do so with the class, set the SubscriptionIdentifier configuration setting before calling subscribe. To update the identifier, call subscribe with a new SubscriptionIdentifier.

To verify that a server supports subscription identifiers, check the "SubscriptionIdentifiersAvailable" value in the ConnAckProperties configuration setting. See the SubscriptionIdentifiers property of the MQTTMessage type for details on returning the ids associated with messages.

Note that a topic may have multiple identifiers associated with it (due to wildcards), and the same identifier may be associated with multiple topics.

Subscription Options Example mqtt1.Connected = true; mqtt1.OnMessageAck += (o, e) => { String ids = mqtt1.IncomingMessages[e.Index].SubscriptionIdentifiers; // ids = "123,321" }; mqtt1.Config("SubscriptionIdentifier=123"); mqtt1.Subscribe("test_topic/subtopic", 1); mqtt1.Config("SubscriptionIdentifier=321"); mqtt1.Subscribe("test_topic/+", 1); mqtt2.Connected = true; mqtt2.PublishMessage("test_topic/subtopic", 1, "hello world");

unsubscribe Method

Unsubscribes the class from one or more topic filters.

Syntax

def unsubscribe(topic_filter: str) -> None: ...

Remarks

This method unsubscribes the class from one or more topic filters. The string passed for TopicFilter must contain one or more valid topic filter strings, separated by the delimiter string specified by the TopicDelimiter configuration setting (, by default).

The on_unsubscribed event will fire when the server has acknowledged the unsubscribe request. However, note that the server's acknowledgment doesn't specify which topics a client was unsubscribed from. Please refer to the on_unsubscribed event for more information.

To successfully unsubscribe from a topic filter, the exact filter must be passed to unsubscribe, regardless of whether or not if contains wildcards. The server ignores any topic filters in an unsubscribe request which do not exactly match that of an existing subscription.

It is impossible to partially unsubscribe from a topic filter with wildcards (that is, if a client is subscribed to a topic filter home/floor1/+/#, requesting to unsubscribe from a topic filter home/floor1/livingRoom/temperature does nothing).

Similarly, because topic filters in an unsubscribe request are simply compared character-by-character with existing subscriptions rather than being interpreted, it is not possible to perform an action such as unsubscribing from all currently subscribed topics by passing "#" for TopicFilter.

Unsubscribe Example // Unsubscribe from topic filters; have to use the exact same strings as before. If this // was to be called after calling the code example shown for the Subscribe() method, we // would still be subscribed to the "home" topic filter. mqtt1.Unsubscribe("home/floor1/+/temperature,home/floor2/#");

on_connected Event

This event is fired immediately after a connection completes (or fails).

Syntax

class MQTTConnectedEventParams(object):
  @property
  def status_code() -> int: ...

  @property
  def description() -> str: ...

# In class MQTT:
@property
def on_connected() -> Callable[[MQTTConnectedEventParams], None]: ...
@on_connected.setter
def on_connected(event_hook: Callable[[MQTTConnectedEventParams], None]) -> None: ...

Remarks

If the connection is made normally, StatusCode is 0 and Description is "OK".

If the connection fails, StatusCode has the error code returned by the Transmission Control Protocol (TCP)/IP stack. Description contains a description of this code. The value of StatusCode is equal to the value of the error.

Please refer to the Error Codes section for more information.

on_connection_status Event

This event is fired to indicate changes in the connection state.

Syntax

class MQTTConnectionStatusEventParams(object):
  @property
  def connection_event() -> str: ...

  @property
  def status_code() -> int: ...

  @property
  def description() -> str: ...

# In class MQTT:
@property
def on_connection_status() -> Callable[[MQTTConnectionStatusEventParams], None]: ...
@on_connection_status.setter
def on_connection_status(event_hook: Callable[[MQTTConnectionStatusEventParams], None]) -> None: ...

Remarks

The on_connection_status event is fired when the connection state changes: for example, completion of a firewall or proxy connection or completion of a security handshake.

The ConnectionEvent parameter indicates the type of connection event. Values may include the following:

on_disconnected Event

This event is fired when a connection is closed.

Syntax

class MQTTDisconnectedEventParams(object):
  @property
  def status_code() -> int: ...

  @property
  def description() -> str: ...

# In class MQTT:
@property
def on_disconnected() -> Callable[[MQTTDisconnectedEventParams], None]: ...
@on_disconnected.setter
def on_disconnected(event_hook: Callable[[MQTTDisconnectedEventParams], None]) -> None: ...

Remarks

If the connection is broken normally, StatusCode is 0 and Description is "OK".

If the connection is broken for any other reason, StatusCode has the error code returned by the Transmission Control Protocol (TCP/IP) subsystem. Description contains a description of this code. The value of StatusCode is equal to the value of the TCP/IP error.

Please refer to the Error Codes section for more information.

on_error Event

Fired when information is available about errors during data delivery.

Syntax

class MQTTErrorEventParams(object):
  @property
  def error_code() -> int: ...

  @property
  def description() -> str: ...

# In class MQTT:
@property
def on_error() -> Callable[[MQTTErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[MQTTErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

on_log Event

Fires once for each log message.

Syntax

class MQTTLogEventParams(object):
  @property
  def log_level() -> int: ...

  @property
  def message() -> str: ...

  @property
  def log_type() -> str: ...

# In class MQTT:
@property
def on_log() -> Callable[[MQTTLogEventParams], None]: ...
@on_log.setter
def on_log(event_hook: Callable[[MQTTLogEventParams], None]) -> None: ...

Remarks

This event fires once for each log message generated by the class. The verbosity is controlled by the LogLevel setting.

LogLevel indicates the level of the Message. Possible values are:

LogType identifies the type of log entry. Possible values are:

• Info: General information about the class.
• Packet: Packet content logging.
• Reconnect: Reconnection status messages.
• Session: Session status messages.

on_message_ack Event

Fired when an incoming or outgoing message has completed all acknowledgment steps.

Syntax

class MQTTMessageAckEventParams(object):
  @property
  def packet_id() -> int: ...

  @property
  def direction() -> int: ...

  @property
  def index() -> int: ...

  @property
  def response_code() -> int: ...

# In class MQTT:
@property
def on_message_ack() -> Callable[[MQTTMessageAckEventParams], None]: ...
@on_message_ack.setter
def on_message_ack(event_hook: Callable[[MQTTMessageAckEventParams], None]) -> None: ...

Remarks

The on_message_ack event fires once an incoming or outgoing message with a QoS of 1 or 2 has successfully completed all acknowledgment steps as required by its QoS level. (Note that this event does not fire for messages with a QoS of 0 since they do not require acknowledgment.)

• PacketId: The Id of the original PUBLISH packet for the message.
• Direction: Shows whether the client (0) or the server (1) is sending the data.
• Index: The index at which the message resides in either the IncomingMessage* properties or OutgoingMessage* properties.
• ResponseCode: In MQTT 5, all response packets contain Reason Codes. This argument contains any code encountered in message acknowledgment packets (PUBACK, PUBREC, PUBREL, PUBCOMP).

Possible MQTT-specific values for ResponseCode are:

Inbound Message Processing

Incoming messages with a QoS of 1 follow these steps:

1. The message is added to IncomingMessage* when the class receives the PUBLISH packet.
2. The class sends a PUBACK (publish acknowledgment) packet in response.
3. The on_message_ack event is fired.
4. The message is removed from IncomingMessage*.
5. The on_message_in event is fired.

Incoming messages with a QoS of 2 follow these steps:

1. The message is added to IncomingMessage* when the class receives the PUBLISH packet.
2. The class sends a PUBREC (publish received) packet in response.
3. The class waits to receive a PUBREL (publish release) packet.
4. The class sends a PUBCOMP (publish complete) packet in response.
5. The on_message_ack event is fired.
6. The message is removed from IncomingMessage*.
7. The on_message_in event is fired.

Outbound Message Processing

Outgoing messages with a QoS of 1 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBACK (publish acknowledgment) packet.
3. The on_message_ack event is fired.
4. The message is removed from OutgoingMessage*.
5. The on_message_out event is fired.

Outgoing messages with a QoS of 2 follow these steps:

1. The class sends the PUBLISH packet, then adds the message to OutgoingMessage*.
2. The class waits to receive a PUBREC (publish received) packet.
3. The class sends a PUBREL (publish release) packet in response.
4. The class waits to receive a PUBCOMP (publish complete) packet.
5. The on_message_ack event is fired.
6. The message is removed from OutgoingMessage*.
7. The on_message_out event is fired.

In MQTT 3.1.1, the RepublishInterval configuration setting, if set to a non-zero value (default), controls how long the class will wait to receive a PUBACK (for QoS 1) or PUBREC (for QoS 2) before automatically republishing an outgoing message. In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC.

on_message_in Event

Fired when an incoming message has been received and/or fully acknowledged.

Syntax

class MQTTMessageInEventParams(object):
  @property
  def packet_id() -> int: ...

  @property
  def topic() -> str: ...

  @property
  def qos() -> int: ...

  @property
  def message() -> bytes: ...

  @property
  def retained() -> bool: ...

  @property
  def duplicate() -> bool: ...

# In class MQTT:
@property
def on_message_in() -> Callable[[MQTTMessageInEventParams], None]: ...
@on_message_in.setter
def on_message_in(event_hook: Callable[[MQTTMessageInEventParams], None]) -> None: ...

Remarks

The on_message_in event fires once for each incoming message either immediately after it is received (QoS 0), or after it has been fully acknowledged (QoS 1 and 2).

• PacketId: The message packet Id. This will always be -1 if QOS is 0.
• Topic: The message's topic string.
• QOS: The message's QoS level.
• Message: The message data.
• Retained: Whether or not this message was received as a result of subscribing to a topic.
• Duplicate: Whether or not the server has indicated that this message is a duplicate of another message sent previously.

Refer to on_message_ack for more information about QoS 1 and 2 message processing steps.

// MessageIn event handler. mqtt1.OnMessageIn += (s, e) => { Console.WriteLine("Received message from topic '" + e.Topic + "' with QoS " + e.QOS + ":"); Console.WriteLine(e.Message); };

on_message_out Event

Fired when an outgoing message has been sent and/or fully acknowledged.

Syntax

class MQTTMessageOutEventParams(object):
  @property
  def packet_id() -> int: ...

  @property
  def topic() -> str: ...

  @property
  def qos() -> int: ...

  @property
  def message() -> bytes: ...

  @property
  def retained() -> bool: ...

  @property
  def duplicate() -> bool: ...

# In class MQTT:
@property
def on_message_out() -> Callable[[MQTTMessageOutEventParams], None]: ...
@on_message_out.setter
def on_message_out(event_hook: Callable[[MQTTMessageOutEventParams], None]) -> None: ...

Remarks

The on_message_out event fires once for each outgoing message either immediately after it is sent (QoS 0), or after it has been fully acknowledged by the receiver (QoS 1 and 2).

• PacketId: The message packet Id. This will always be -1 if QOS is 0.
• Topic: The message's topic string.
• QOS: The message's QoS level.
• Message: The message data.
• Retained: Whether or not this message was sent with the "Retain" flag set.
• Duplicate: Whether or not this message was sent with the "Duplicate" flag set.

Refer to on_message_ack for more information about QoS 1 and 2 message processing steps.

// MessageOut event handler. mqtt1.OnMessageOut += (s, e) => { Console.WriteLine("Send message to topic '" + e.Topic + "' with QoS " + e.QOS + ":"); Console.WriteLine(e.Message); };

on_ready_to_send Event

Fired when the class is ready to send data.

Syntax

class MQTTReadyToSendEventParams(object):
# In class MQTT:
@property
def on_ready_to_send() -> Callable[[MQTTReadyToSendEventParams], None]: ...
@on_ready_to_send.setter
def on_ready_to_send(event_hook: Callable[[MQTTReadyToSendEventParams], None]) -> None: ...

Remarks

The on_ready_to_send event indicates that the underlying TCP/IP subsystem is ready to accept data after a call to publish_data or publish_message fails due to a WOULDBLOCK condition. The event is also fired immediately after a connection to the remote host is established.

on_ssl_server_authentication Event

Fired after the server presents its certificate to the client.

Syntax

class MQTTSSLServerAuthenticationEventParams(object):
  @property
  def cert_encoded() -> bytes: ...

  @property
  def cert_subject() -> str: ...

  @property
  def cert_issuer() -> str: ...

  @property
  def status() -> str: ...

  @property
  def accept() -> bool: ...
  @accept.setter
  def accept(value) -> None: ...

# In class MQTT:
@property
def on_ssl_server_authentication() -> Callable[[MQTTSSLServerAuthenticationEventParams], None]: ...
@on_ssl_server_authentication.setter
def on_ssl_server_authentication(event_hook: Callable[[MQTTSSLServerAuthenticationEventParams], None]) -> None: ...

Remarks

During this event, the client can decide whether or not to continue with the connection process. The Accept parameter is a recommendation on whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

When Accept is False, Status shows why the verification failed (otherwise, Status contains the string OK). If it is decided to continue, you can override and accept the certificate by setting the Accept parameter to True.

on_ssl_status Event

Fired when secure connection progress messages are available.

Syntax

class MQTTSSLStatusEventParams(object):
  @property
  def message() -> str: ...

# In class MQTT:
@property
def on_ssl_status() -> Callable[[MQTTSSLStatusEventParams], None]: ...
@on_ssl_status.setter
def on_ssl_status(event_hook: Callable[[MQTTSSLStatusEventParams], None]) -> None: ...

Remarks

The event is fired for informational and logging purposes only. This event tracks the progress of the connection.

on_subscribed Event

Fires for each topic filter subscription the server acknowledges.

Syntax

class MQTTSubscribedEventParams(object):
  @property
  def topic_filter() -> str: ...

  @property
  def qos() -> int: ...

  @property
  def response_code() -> int: ...

# In class MQTT:
@property
def on_subscribed() -> Callable[[MQTTSubscribedEventParams], None]: ...
@on_subscribed.setter
def on_subscribed(event_hook: Callable[[MQTTSubscribedEventParams], None]) -> None: ...

Remarks

This event fires each time the server has acknowledged a topic filter subscription request (that is, calling subscribe with multiple topic filters will cause this to fire multiple times).

• TopicFilter: The topic filter subscription request being acknowledged.
• QOS: The QoS level the server has granted for the subscription.
• ResponseCode: Indicates the result of the subscription request.

Possible values for ResponseCode are:

• 0: Success, QoS 0 granted
• 1: Success, QoS 1 granted
• 2: Success, QoS 2 granted
• 128: Unspecified error
• 131: Implementation specific error; The SUBSCRIBE is valid but the Server does not accept it.
• 135: Not authorized; The Client is not authorized to make this subscription.
• 143: Topic Filter invalid; The Topic Filter is correctly formed but is not allowed for this Client.
• 145: Packet Identifier in use
• 151: Quota exceeded; An implementation or administrative imposed limit has been exceeded.
• 158: Shared Subscriptions not supported
• 161: Shared Subscriptions not supported
• 162: Wildcard Subscriptions not supported

Keep in mind that the server may have chosen to grant a lower QoS than was requested under certain circumstances (e.g., if the server doesn't support the requested QoS).

Note: the server is not required to acknowledge a subscription before it begins delivering messages for that subscription.

on_unsubscribed Event

Fires when the server has acknowledged an unsubscribe request.

Syntax

class MQTTUnsubscribedEventParams(object):
  @property
  def topic_filters() -> str: ...

  @property
  def response_code() -> int: ...

# In class MQTT:
@property
def on_unsubscribed() -> Callable[[MQTTUnsubscribedEventParams], None]: ...
@on_unsubscribed.setter
def on_unsubscribed(event_hook: Callable[[MQTTUnsubscribedEventParams], None]) -> None: ...

Remarks

This event fires when the server has acknowledged an unsubscribe request sent with unsubscribe (that is, unlike the on_subscribed event, this event fires only once for each call to unsubscribe, regardless of how many topic filters are passed to it).

Note that in MQTT 3.1.1, servers do not specify which topic filters a client has been successfully unsubscribed in their acknowledgments. In fact, they will still acknowledge an unsubscribe request even if none of the topic filters included matched existing subscriptions. It is up to the client to keep track of what topics it is subscribed to; the TopicFilters parameter is provided as a convenience, its value simply a copy of the value passed to unsubscribe originally.

Possible values for ResponseCode are:

• 0: Success; The subscription is deleted.
• 17: No subscription existed; No matching Topic Filter is being used by the Client.
• 128: Unspecified error; The unsubscribe could not be completed and the Server either does not wish to reveal the reason or none of the other Reason Codes apply.
• 131: Implementation specific error; The UNSUBSCRIBE is valid but the Server does not accept it.
• 135: Not authorized; The Client is not authorized to unsubscribe.
• 143: Topic Filter invalid; The Topic Filter is correctly formed but is not allowed for this Client.
• 145: Packet Identifier in use; The specified Packet Identifier is already in use.

MQTT Config Settings

MQTT Config Settings

{ 
  "ClientTopicAliasMax":"20",
  "MaximumPacketSize":"128000",
  "ReceiveMaximum":"12",
  "RequestResponseInformation":"false",
  "RequestProblemInformation":"true",
  "SessionExpInterval":"1234"
}

{
  "ContentType":"plain/text",
  "CorrelationData":"00000000",
  "MessageExpInterval":"1000",
  "PayloadFormatIndicator":"1",
  "ResponseTopic": "ResponseTopic",
  "TopicAlias":"1",
  "UserProperty":"prp1:val1",
  "UserProperty":"prp2:val2"
}

{
"ContentType":"text/plain",
"CorrelationData":"00000000",
"MessageExpInterval":"3600",
"PayloadFormatIndicator":"1",
"ResponseTopic": "ResponseTopic",
"WillDelayInterval":"10"
}

TCPClient Config Settings

SSL Config Settings

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

Socket Config Settings

MQTT Errors

MQTT Errors

WebSocket Errors

HTTP Errors

The class may also return one of the following error codes, which are inherited from other classes.

TCPClient Errors

SSL Errors

TCP/IP Errors