IPWorks IoT 2022 ActiveX Edition
Version 22.0 [Build 8369]

MQTTSN Control

Properties   Methods   Events   Config Settings   Errors  

A lightweight, fully-featured MQTT-SN client implementation.

Syntax

MQTTSN

Remarks

The MQTTSN control provides a lightweight, fully-featured MQTT-SN (MQTT for Sensor Networks) client implementation over UDP.

Connecting

Connecting to a gateway is easy; in the simplest case, set the ClientId property and call the ConnectTo method, passing it the gateway's hostname and port number.

When connecting to an MQTT gateway, the control sends the following information:

Refer to CleanSession for more information about MQTT sessions; refer to WillTopic, WillMessage, WillQOS and WillRetain for more information about MQTT Wills.

Basic Connection Example mqttsn1.ClientId = "testClient"; mqttsn1.CleanSession = true; mqttsn1.KeepAliveInterval = 30; mqttsn1.WillTopic = "wills/" + mqttsn1.ClientId; mqttsn1.WillMessage = mqttsn1.ClientId + " was disconnected ungracefully!"; mqttsn1.ConnectTo(host, port);

Topic Subscriptions

The Subscribe and Unsubscribe methods are used to subscribe to and unsubscribe from topics.

When subscribing, pass the topic name or id, topic id type and QoS level. Topic filters may contain wildcards in order to match multiple topics on the server. If a topic name is specified, the SubscribedTopicId configuration setting will contain the assigned id for the topic.

Subscribe Examples String fullTopicName = "full/topic/name"; mqttsn1.Subscribe(fullTopicName, 0, 2); // subscribe with topic name int assignedTopicId = mqttsn1.Config("SubscribedTopicId"); // map id to topic name used mqttsn1.Subscribe(fullTopicName+"/#", 0, 2) // topic name with wildcard; SubscribedTopicId will be 0 mqttsn1.OnTopicId += (s,e) => { // will fire before messages matching the wildcard are sent to the client int topicId = e.TopicId; String topicName = e.TopicName; // establish mapping between these }; mqttsn1.Subscribe("aa", 2, 2); // subscribe with short topic name; no need for registration

After subscribing to topics, any messages received on that topic will cause the MessageIn event to fire. Refer to MessageIn for more information about processing steps for inbound messages.

When unsubscribing, pass the topic id or exact topic name used to subscribe.

Unsubscribe Examples String fullTopicName = "full/topic/name"; mqtt1.Unsubscribe(fullTopicName, 0); // unsubscribe from topic name mqtt1.Unsubscribe(fullTopicName+"/#", 0); // must use full topic filter if includes wildcard; can't unsubscribe from individual topics included in the filter mqtt1.Unsubscribe("aa", 2); // unsubscribe from short topic

Refer to Subscribe and Unsubscribe for more information about subscriptions and topic names.

Publishing Messages

To publish messages to topics, use the PublishMessage and PublishData methods.

PublishMessage is used to publish a message with a string payload, while PublishData is used to publish a message with a raw data payload. Both also accept the topic id to publish to, the topic id type and a QoS level at which to publish.

Publish Examples // Publish string messages int id = mqttsn1.RegisterTopic("topic/name"); // must register topic names that are not short or pre-defined mqttsn1.PublishMessage(id, 0, 2, "hello"); // publish message with registered topic name mqttsn1.PublishMessage("aa", 2, 2, "hello"); // publish message with short topic name // Publish a raw data message. byte[] picture = ...; mqtt1.PublishData(id, 0, 2, picture);

Refer to PublishData and PublishMessage for more information about message publishing as well as topic names.

Sleeping

To save battery, clients may enter a sleep state in which their messages will be buffered for them. To manage sleeping, use StartSleep and StopSleep. To receive all buffered messages then return to sleep, use FetchMessages.

If the client exceeds the sleep duration passed to StartSleep without waking or sending any packets, it will be considered lost and will disconnect.

Sleep Examples mqttsn1.StartSleep(8); // sleep for 8 seconds // ... wait for 5 seconds mqttsn1.FetchMessages(); // MessageIn will fire for each message buffered during that time // ... wait for 5 more seconds (ok because <8 seconds since last packet sent) mqttsn1.StopSleep();

Property List


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

CleanSessionDetermines whether a clean session is used once connected.
ClientIdA string that uniquely identifies this instance of the control to the server.
ConnectedTriggers a connection or disconnection.
KeepAliveIntervalThe maximum period of inactivity the gateway should allow between receiving messages from the client.
LocalHostThe name of the local host or user-assigned IP interface through which connections are initiated or accepted.
LocalPortThe UDP port in the local host where UDP binds.
RemoteHostThe address of the remote host. Domain names are resolved to IP addresses.
RemotePortThe UDP port in the remote host.
TimeoutA timeout for the control.
WillMessageThe message that the server should publish in the event of an ungraceful disconnection.
WillTopicThe topic that the server should publish the WillMessage to in the event of an ungraceful disconnection.

Method List


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

ConfigSets or retrieves a configuration setting.
ConnectConnects to the MQTTSN Gateway.
ConnectToConnects to the remote host.
DisconnectDisconnect from the MQTTSN Gateway.
DiscoverGatewayBroadcast a SEARCHGW message to network clients and gateways.
DoEventsProcesses events from the internal message queue.
FetchMessagesReceive currently buffered messages and return to sleep.
PingSend a PINGREQ message to the gateway to reset the Keep Alive interval and ensure the gateway's liveliness.
PublishDataPublishes a message with a raw data payload.
PublishMessagePublishes a message with a string payload.
RegisterTopicRegister a topic name. Returns the topic id mapped to the newly registered topic name.
ResetReset the control.
SendDiscoverResponseAsynchronously respond to a SEARCHGW message received from a peer.
StartSleepEnter sleep state for the specified duration.
StopSleepEnter active state, ending the sleep period.
SubscribeSubscribes the control to the specified topic.
UnsubscribeUnsubscribes the control from the specified topic.
UpdateWillMessageUpdate the will message stored in session state data by the server.
UpdateWillTopicUpdate the will topic, will QoS and will retain flag stored in session state data by the server.

Event List


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

ConnectedFired after a MQTTSN connection completes (or fails).
DisconnectedFired when a MQTTSN connection is closed.
DiscoverRequestFired when the control receives a SEARCHGW packet from another client.
ErrorInformation about errors during data delivery.
GatewayInfoFired when the control receives a GWINFO or ADVERTISE packet.
LogFires once for each log message.
MessageInFired when an incoming message has been received and/or fully acknowledged.
TopicInfoFired when the client receives a REGISTER packet from the gateway assigning a topic id to a topic name.

Config Settings


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

ConnectionTimeoutHow long to wait for a connection attempt to succeed.
DuplicateWhether to set the Duplicate flag when publishing a message.
LogLevelThe level of detail that is logged.
PingTimeoutLength of time to wait for a PINGRESP packet.
RetainWhether to set the Retain flag when publishing a message.
SubscribedTopicIdTopic id assigned by the gateway when a topic name is used in a SUBSCRIBE message.
SubscribeDUPWhether to set the Duplicate flag when subscribe to a topic.
WillQOSThe QoS value to use for the Will message.
WillRetainWhether the server should retain the Will message after publishing it.
CodePageThe system code page used for Unicode to Multibyte translations.
UseInternalSecurityAPITells the control whether or not to use the system security libraries or an internal implementation.

CleanSession Property (MQTTSN Control)

Determines whether a clean session is used once connected.

Syntax

mqttsncontrol.CleanSession[=boolean]

Default Value

True

Remarks

This property determines whether or not the control 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, CleanSession is true, so the server will discard any state data previously associated with the current ClientId once the control has connected successfully. In addition, the server will not save any state data when the control disconnects.

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

The server-side session state consists of:

  • client subscriptions,
  • QoS 1 and 2 messages which are buffering or unacknowledged,
  • QoS 2 messages received from the client but not completely acknowledged, and
  • the WillMessage and WillTopic if set.

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

This property is not available at design time.

Data Type

Boolean

ClientId Property (MQTTSN Control)

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

Syntax

mqttsncontrol.ClientId[=string]

Default Value

""

Remarks

The ClientId string is used by the server to uniquely identify each client that is connected to it.

If ClientId is empty when Connect is called, the control's behavior depends on value of CleanSession. If CleanSession is True, the control will automatically generate a unique value for ClientId before connecting. If CleanSession is False, the control fails with an error.

This property is not available at design time.

Data Type

String

Connected Property (MQTTSN Control)

Triggers a connection or disconnection.

Syntax

mqttsncontrol.Connected[=boolean]

Default Value

False

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the control send a CONNECT packet to the MQTTSN Gateway identified by the RemoteHost property. If successful, after the connection is achieved the value of the property changes to True and the Connected event is fired.

Setting this property to False sends a DISCONNECT packet, closing the connection.

When connecting to an MQTT gateway, the control sends the following information:

Refer to CleanSession for more information about MQTT sessions; refer to WillTopic, WillMessage, WillQOS and WillRetain for more information about MQTT Wills.

Basic Connection Example mqttsn1.ClientId = "testClient"; mqttsn1.CleanSession = true; mqttsn1.KeepAliveInterval = 30; mqttsn1.WillTopic = "wills/" + mqttsn1.ClientId; mqttsn1.WillMessage = mqttsn1.ClientId + " was disconnected ungracefully!"; mqttsn1.RemoteHost = host; mqttsn1.RemotePort = port; mqttsn1.Connect();

This property is not available at design time.

Data Type

Boolean

KeepAliveInterval Property (MQTTSN Control)

The maximum period of inactivity the gateway should allow between receiving messages from the client.

Syntax

mqttsncontrol.KeepAliveInterval[=integer]

Default Value

0

Remarks

The KeepAliveInterval, if set to a non-zero value, is the maximum number of seconds that the gateway will allow the connection to be idle without receiving a message from the client. The value of KeepAliveInterval is sent to the server when Connect is called; it cannot be changed when the control is already connected.

MQTT servers are required to measure periods of inactivity for all clients who specify a non-zero KeepAliveInterval, and must consider them lost if they have not communicated within the KeepAliveInterval. The gateway will activate the Will feature for lost clients.

To maintain the connection, the server must send a PINGREQ (ping request) packet within the KeepAliveInterval seconds after the most recent message sent. For more see the Ping method.

Similarly, if the control doesn't receive a PINGRESP (ping response) packet after multiple retransmissions of the PINGREQ packet, it should first try to connect to another gateway before trying to re-connect to the original one.

If KeepAliveInterval is set to 0 (default), the server is not required to consider inactivity. Note that, regardless of keep-alive settings, the server is always free to disconnect clients it deems "unresponsive".

This property is not available at design time.

Data Type

Integer

LocalHost Property (MQTTSN Control)

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

Syntax

mqttsncontrol.LocalHost[=string]

Default Value

""

Remarks

The LocalHost 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 control initiate connections (or accept in the case of server controls) only through that interface.

If the control is connected, the LocalHost 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: LocalHost is not persistent. You must always set it in code, and never in the property window.

Data Type

String

LocalPort Property (MQTTSN Control)

The UDP port in the local host where UDP binds.

Syntax

mqttsncontrol.LocalPort[=integer]

Default Value

0

Remarks

The LocalPort property must be set before UDP is activated (Active is set to True). It instructs the control to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the TCP/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

LocalPort cannot be changed once the control is Active. Any attempt to set the LocalPort property when the control is Active will generate an error.

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

Data Type

Integer

RemoteHost Property (MQTTSN Control)

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

Syntax

mqttsncontrol.RemoteHost[=string]

Default Value

""

Remarks

The RemoteHost property specifies the IP address (IP number in dotted internet format) or Domain Name of the remote host.

If RemoteHost is set to 255.255.255.255, the control broadcasts data on the local subnet.

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

If UseConnection is set to True, the RemoteHost must be set before the control is activated (Active is set to True).

Data Type

String

RemotePort Property (MQTTSN Control)

The UDP port in the remote host.

Syntax

mqttsncontrol.RemotePort[=integer]

Default Value

0

Remarks

The RemotePort is the UDP port on the RemoteHost to send UDP datagrams to.

A valid port number (a value between 1 and 65535) is required.

If UseConnection is set to True, the RemotePort must be set before the control is activated (Active is set to True).

Data Type

Integer

Timeout Property (MQTTSN Control)

A timeout for the control.

Syntax

mqttsncontrol.Timeout[=integer]

Default Value

60

Remarks

This property defines the timeout when sending data. A value of 0 means data will be sent asynchronously and a positive value means data is sent synchronously.

The control will use DoEvents 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 component throws an exception. 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.

Data Type

Integer

WillMessage Property (MQTTSN Control)

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

Syntax

mqttsncontrol.WillMessage[=string]

Default Value

""

Remarks

This property may be set before calling Connect to specify to the server a message that should be published on WillTopic if the connection is closed ungracefully or lost.

The WillMessage will only be sent to the server when Connect is called if WillTopic is set. Note that in MQTTSN the clean session concept is extended to will topic and will message. The WillMessage can be updated with the UpdateWillMessage method.

Refer to WillTopic for more information about MQTT Will functionality.

This property is not available at design time.

Data Type

String

WillTopic Property (MQTTSN Control)

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

Syntax

mqttsncontrol.WillTopic[=string]

Default Value

""

Remarks

This property may be set before calling Connect to specify the topic name that the server should publish the WillMessage on if the connection is closed ungracefully or lost.

MQTT Wills

The Will feature of MQTT allows a client to specify to the server a WillMessage to publish (as well as a WillTopic to publish it on) in the event that the server considers the client lost or ungracefully disconnected.

An "ungraceful disconnection" is any disconnection other than one triggered by calling Disconnect. If the client enters sleep mode, the server will not publish the Will. However, if the client is lost as a result of exceeding the sleep duration without sending a message, the server will publish the Will.

In addition to the WillTopic and WillMessage 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 WillTopic is set to empty string (default) when Connect is called, the control will not send a Will to the server.

In MQTTSN, the WillTopic, WillMessage, WillQOS and WillRetain may all be updated using the UpdateWillMessage and UpdateWillTopic methods.

This property is not available at design time.

Data Type

String

Config Method (MQTTSN Control)

Sets or retrieves a configuration setting.

Syntax

mqttsncontrol.Config ConfigurationString

Remarks

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

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, 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 (MQTTSN Control)

Connects to the MQTTSN Gateway.

Syntax

mqttsncontrol.Connect 

Remarks

This method connects to the MQTTSN Gateway, specified by RemoteHost and RemotePort, by sending a CONNECT packet. Calling this method is equivalent to setting the Connected property to True.

When connecting to an MQTT gateway, the control sends the following information:

Refer to CleanSession for more information about MQTT sessions; refer to WillTopic, WillMessage, WillQOS and WillRetain for more information about MQTT Wills.

Basic Connection Example mqttsn1.ClientId = "testClient"; mqttsn1.CleanSession = true; mqttsn1.KeepAliveInterval = 30; mqttsn1.WillTopic = "wills/" + mqttsn1.ClientId; mqttsn1.WillMessage = mqttsn1.ClientId + " was disconnected ungracefully!"; mqttsn1.RemoteHost = host; mqttsn1.RemotePort = port; mqttsn1.Connect();

ConnectTo Method (MQTTSN Control)

Connects to the remote host.

Syntax

mqttsncontrol.ConnectTo Host, Port

Remarks

This method connects to the MQTTSN Gateway, specified by Host and Port, by sending a CONNECT packet. Calling this method is equivalent to setting the RemoteHost property to Host, setting RemotePort to Port, and then setting the Connected property to True.

When connecting to an MQTT gateway, the control sends the following information:

Refer to CleanSession for more information about MQTT sessions; refer to WillTopic, WillMessage, WillQOS and WillRetain for more information about MQTT Wills.

Basic Connection Example mqttsn1.ClientId = "testClient"; mqttsn1.CleanSession = true; mqttsn1.KeepAliveInterval = 30; mqttsn1.WillTopic = "wills/" + mqttsn1.ClientId; mqttsn1.WillMessage = mqttsn1.ClientId + " was disconnected ungracefully!"; mqttsn1.ConnectTo(host, port);

Disconnect Method (MQTTSN Control)

Disconnect from the MQTTSN Gateway.

Syntax

mqttsncontrol.Disconnect 

Remarks

This method disconnects from the MQTTSN Gateway by sending a DISCONNECT packet. Calling this method is equivalent to setting the Connected property to False.

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

DiscoverGateway Method (MQTTSN Control)

Broadcast a SEARCHGW message to network clients and gateways.

Syntax

mqttsncontrol.DiscoverGateway BroadcastRadius

Remarks

Broadcast a SEARCHGW message in order to discover nearby gateways. Network clients and gateways may respond with a GWINFO message containing a gateway id. Such a response will trigger the GatewayInfo event.

This functionality is not yet implemented.

DoEvents Method (MQTTSN Control)

Processes events from the internal message queue.

Syntax

mqttsncontrol.DoEvents 

Remarks

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

FetchMessages Method (MQTTSN Control)

Receive currently buffered messages and return to sleep.

Syntax

mqttsncontrol.FetchMessages 

Remarks

Request any messages currently being buffered by the server for the current sleep period and return to sleep after they have been received.

Any available buffered messages will be sent to the client by the MQTTSN Gateway and the sleep interval will be reset.

This method sends a PINGREQ method with the ClientId, requesting buffered messages which will be sent if available (see MessageIn). When the server has sent all messages, it will sent a PINGRESP message, causing the client to re-enter sleep mode. Once the PINGRESP is received, the duration the client may sleep restarts.

Ping Method (MQTTSN Control)

Send a PINGREQ message to the gateway to reset the Keep Alive interval and ensure the gateway's liveliness.

Syntax

mqttsncontrol.Ping 

Remarks

The client must send a PINGREQ message using this method during each KeepAliveInterval period. If the client does not send any message to the gateway during this period, it will be considered lost and will disconnect.

The client also uses this message to supervise the liveliness of the gateway to which they are connected. If a client does not receive a PINGRESP from the gateway even after multiple retransmissions of the PINGREQ message, it should first try to connect to another gateway before trying to re-connect to this gateway.

See KeepAliveInterval for more information.

For more detailed requirements regarding Keep Alive intervals and reconnection, refer to the MQTTSN specification.

PublishData Method (MQTTSN Control)

Publishes a message with a raw data payload.

Syntax

mqttsncontrol.PublishData TopicId, TopicIdType, QOS, Data

Remarks

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

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

Note that the control will only allow one publish flow at a time.

Publish Examples // Publish string messages int id = mqttsn1.RegisterTopic("topic/name"); // must register topic names that are not short or pre-defined mqttsn1.PublishMessage(id, 0, 2, "hello"); // publish message with registered topic name mqttsn1.PublishMessage("aa", 2, 2, "hello"); // publish message with short topic name // Publish a raw data message. byte[] picture = ...; mqtt1.PublishData(id, 0, 2, picture);

Topic Ids

A topic id is a short identifier corresponding to a longer topic name which is used in MQTTSN due to the limited bandwidth and small message payload in wireless sensor networks.

The type of topic id sent with the message must be specified. TopicIdType may have the following values:

  • 0: Registered topic id
  • 1: Pre-defined topic id
  • 2: Short topic name

A registered topic id identifies a topic name registered with the server before the time of the message. To register a topic id for a given topic name with the gateway so that messages may be published to that topic using that topic id, use the RegisterTopic method.

A pre-defined topic id is one whose mapping to a topic name is known in advance by both the client and the gateway - no registration is necessary.

A short topic name has a fixed length of two bytes and is short enough that no registration is necessary. To use one, simply set the correct TopicIdType and set the TopicId to a two-character string.

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.

QoS Values

QoS values set the service level for delivery of a message. Values range from -1 to 2 and have the following meanings:

QoS LevelDescription
-1 Simple publish - No connection, registration or subscription needed.
0 At most once - The published message is sent once, and if it does not arrive it is lost.
1 At least once - Guarantees that the published message arrives, but there may be duplicates.
2 Exactly once - Guarantees that the publish message arrives and that there are no duplicates.

To send a message with QoS -1, simply set RemoteHost and RemoteHost and call PublishMessage with a pre-defined topic id or short topic name. No connection or registration is necessary. The client will not be informed whether the gateway address is correct, whether the gateway is alive, or whether the messages arrive at the gateway.

Publish QoS -1 Example mqttsn1 = new Mqttsn(); mqttsn1.RemoteHost = gatewayAddress; mqttsn1.RemotePort = gatewayPort; mqttsn1.PublishMessage("aa", 2, -1, "hello"); // publish QoS -1 message; no connection or registration

Republishing Messages

For QoS 1 and 2 messages, the client is responsible for retransmitting the message if it is not fully acknowledged within a reasonable wait time. To do so, set the Duplicate flag configuration setting and call the publish method again.

After a reasonable amount of retransmission attempts, the client should abort the procedure and assume the gateway has disconnected. It should then try to connect to another gateway, only returning to the original if it fails.

PublishMessage Method (MQTTSN Control)

Publishes a message with a string payload.

Syntax

mqttsncontrol.PublishMessage TopicId, TopicIdType, QOS, Message

Remarks

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

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

Note that the control will only allow one publish flow at a time.

Publish Examples // Publish string messages int id = mqttsn1.RegisterTopic("topic/name"); // must register topic names that are not short or pre-defined mqttsn1.PublishMessage(id, 0, 2, "hello"); // publish message with registered topic name mqttsn1.PublishMessage("aa", 2, 2, "hello"); // publish message with short topic name // Publish a raw data message. byte[] picture = ...; mqtt1.PublishData(id, 0, 2, picture);

Topic Ids

A topic id is a short identifier corresponding to a longer topic name which is used in MQTTSN due to the limited bandwidth and small message payload in wireless sensor networks.

The type of topic id sent with the message must be specified. TopicIdType may have the following values:

  • 0: Registered topic id
  • 1: Pre-defined topic id
  • 2: Short topic name

A registered topic id identifies a topic name registered with the server before the time of the message. To register a topic id for a given topic name with the gateway so that messages may be published to that topic using that topic id, use the RegisterTopic method.

A pre-defined topic id is one whose mapping to a topic name is known in advance by both the client and the gateway - no registration is necessary.

A short topic name has a fixed length of two bytes and is short enough that no registration is necessary. To use one, simply set the correct TopicIdType and set the TopicId to a two-character string.

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.

QoS Values

QoS values set the service level for delivery of a message. Values range from -1 to 2 and have the following meanings:

QoS LevelDescription
-1 Simple publish - No connection, registration or subscription needed.
0 At most once - The published message is sent once, and if it does not arrive it is lost.
1 At least once - Guarantees that the published message arrives, but there may be duplicates.
2 Exactly once - Guarantees that the publish message arrives and that there are no duplicates.

To send a message with QoS -1, simply set RemoteHost and RemoteHost and call PublishMessage with a pre-defined topic id or short topic name. No connection or registration is necessary. The client will not be informed whether the gateway address is correct, whether the gateway is alive, or whether the messages arrive at the gateway.

Publish QoS -1 Example mqttsn1 = new Mqttsn(); mqttsn1.RemoteHost = gatewayAddress; mqttsn1.RemotePort = gatewayPort; mqttsn1.PublishMessage("aa", 2, -1, "hello"); // publish QoS -1 message; no connection or registration

Republishing Messages

For QoS 1 and 2 messages, the client is responsible for retransmitting the message if it is not fully acknowledged within a reasonable wait time. To do so, set the Duplicate flag configuration setting and call the publish method again.

After a reasonable amount of retransmission attempts, the client should abort the procedure and assume the gateway has disconnected. It should then try to connect to another gateway, only returning to the original if it fails.

RegisterTopic Method (MQTTSN Control)

Register a topic name. Returns the topic id mapped to the newly registered topic name.

Syntax

mqttsncontrol.RegisterTopic TopicName

Remarks

Requests that the gateway establish a new topic id mapping for the TopicName provided. If accepted, the gateway assigns a topic id to the received topic name and returns it. At this point, the client may begin sending messages with this topic id.

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.

Reset Method (MQTTSN Control)

Reset the control.

Syntax

mqttsncontrol.Reset 

Remarks

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

SendDiscoverResponse Method (MQTTSN Control)

Asynchronously respond to a SEARCHGW message received from a peer.

Syntax

mqttsncontrol.SendDiscoverResponse GatewayId, GatewayAddress

Remarks

Asynchronously respond to a SEARCHGW message received from a peer. See also DiscoverRequest.

This functionality is not yet implemented.

StartSleep Method (MQTTSN Control)

Enter sleep state for the specified duration.

Syntax

mqttsncontrol.StartSleep Duration

Remarks

When this method is called, the gateway will buffer all incoming messages for the client until the next time it awakes. To receive all currently buffered messages, call StopSleep or FetchMessages.

While in the sleep state, the client no longer must abide by the KeepAliveInterval, but must awake before the end of the sleep duration. If it does not send the gateway any messages in this interval, it will be considered lost and will disconnect.

If FetchMessages is called, the client will return to sleep after receiving the messages and the sleep timer will restart. If StopSleep is called, the client will enter the active state.

Sleep Examples mqttsn1.StartSleep(8); // sleep for 8 seconds // ... wait for 5 seconds mqttsn1.FetchMessages(); // MessageIn will fire for each message buffered during that time // ... wait for 5 more seconds (ok because <8 seconds since last packet sent) mqttsn1.StopSleep();

StopSleep Method (MQTTSN Control)

Enter active state, ending the sleep period.

Syntax

mqttsncontrol.StopSleep 

Remarks

Wake up from the sleep state and receive any messages which were buffered by the gateway during the sleep period. This method must be called before the end of the duration specified in the StartSleep method.

Once active, the client is once again subject to KeepAliveInterval supervision just like after connection.

Subscribe Method (MQTTSN Control)

Subscribes the control to the specified topic.

Syntax

mqttsncontrol.Subscribe TopicId, TopicIdType, QOS

Remarks

This method subscribes the control to the TopicId using the given QoS level.

TopicIdType indicates the category of value specified in TopicId and may have the following values:

  • 0: Topic name - a full topic name as described in RegisterTopic to be registered by the gateway.
  • 1: Pre-defined topic id - id whose mapping to a topic name is known in advance by both the client and the gateway - no registration is necessary.
  • 2: Short topic name - has a fixed length of two bytes and is short enough that no registration is necessary. To use one, simply set the correct TopicIdType and set the TopicId to a two-character string.

If the topic name option is used, the topic id returned with the SUBACK packet will be accessible in the SubscribedTopicId configuration setting. If a topic name with a wildcard character is used, SubscribedTopicId will be 0. When the gateway has a PUBLISH message with a topic name matching the wildcard to be sent to the client, it will follow the registration process described in TopicInfo.

Subscribe Examples String fullTopicName = "full/topic/name"; mqttsn1.Subscribe(fullTopicName, 0, 2); // subscribe with topic name int assignedTopicId = mqttsn1.Config("SubscribedTopicId"); // map id to topic name used mqttsn1.Subscribe(fullTopicName+"/#", 0, 2) // topic name with wildcard; SubscribedTopicId will be 0 mqttsn1.OnTopicId += (s,e) => { // will fire before messages matching the wildcard are sent to the client int topicId = e.TopicId; String topicName = e.TopicName; // establish mapping between these }; mqttsn1.Subscribe("aa", 2, 2); // subscribe with short topic name; no need for registration

Topic Filters

A topic filter is a string which can be passed to TopicId when TopicIdType is 0 and can match one or more topic names.

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

QoS Values

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

QoS LevelDescription
-1 Simple publish - No connection, registration or subscription needed.
0 At most once - The published message is sent once, and if it does not arrive it is lost.
1 At least once - Guarantees that the published message arrives, but there may be duplicates.
2 Exactly once - Guarantees that the publish message arrives and that there are no duplicates.

A QoS value of -1 is not applicable to subscriptions.

Note that if this message is being resent, the SubscribeDUP configuration setting must be enabled. For more details on retransmission intervals and counts, see the MQTTSN specification.

Unsubscribe Method (MQTTSN Control)

Unsubscribes the control from the specified topic.

Syntax

mqttsncontrol.Unsubscribe TopicId, TopicIdType

Remarks

This method unsubscribes the control to the TopicId.

TopicIdType indicates the category of value specified in TopicId and may have the following values:

  • 0: Topic name - a full topic name as described in RegisterTopic to be registered by the gateway.
  • 1: Pre-defined topic id - id whose mapping to a topic name is known in advance by both the client and the gateway - no registration is necessary.
  • 2: Short topic name - has a fixed length of two bytes and is short enough that no registration is necessary. To use one, simply set the correct TopicIdType and set the TopicId to a two-character string.

Unsubscribe Examples String fullTopicName = "full/topic/name"; mqtt1.Unsubscribe(fullTopicName, 0); // unsubscribe from topic name mqtt1.Unsubscribe(fullTopicName+"/#", 0); // must use full topic filter if includes wildcard; can't unsubscribe from individual topics included in the filter mqtt1.Unsubscribe("aa", 2); // unsubscribe from short topic

UpdateWillMessage Method (MQTTSN Control)

Update the will message stored in session state data by the server.

Syntax

mqttsncontrol.UpdateWillMessage 

Remarks

When this message is called, the value of WillMessage will be used to update the will message stored by the server.

This method may be called when this value is empty, in this case the server value will be cleared.

See UpdateWillTopic for more on updating will settings.

UpdateWillTopic Method (MQTTSN Control)

Update the will topic, will QoS and will retain flag stored in session state data by the server.

Syntax

mqttsncontrol.UpdateWillTopic 

Remarks

When this message is called, the value of WillTopic, WillQOS and WillRetain will be used to update the will message stored by the server.

This method may be called when these values are empty, in this case the server values will be cleared.

See UpdateWillMessage for more on updating will settings.

Connected Event (MQTTSN Control)

Fired after a MQTTSN connection completes (or fails).

Syntax

Sub mqttsncontrol_Connected(StatusCode As Integer, Description As String)

Remarks

If no will topic or message is set, this event will fire immediately. If a will topic and the will message are set, this event will be fired after the will packet exchange.

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

Please refer to the Error Codes section for more information.

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

Disconnected Event (MQTTSN Control)

Fired when a MQTTSN connection is closed.

Syntax

Sub mqttsncontrol_Disconnected(StatusCode As Integer, Description As String)

Remarks

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

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

DiscoverRequest Event (MQTTSN Control)

Fired when the control receives a SEARCHGW packet from another client.

Syntax

Sub mqttsncontrol_DiscoverRequest(Radius As Integer, GatewayId As Integer, GatewayAddress As String, Respond As Boolean)

Remarks

This event allows the client to process the received gateway info and decide whether or not to respond to the search request.

If Respond is set to True, the control will respond with a GWINFO packet.

This functionality is not yet implemented.

Error Event (MQTTSN Control)

Information about errors during data delivery.

Syntax

Sub mqttsncontrol_Error(ErrorCode As Integer, Description As String)

Remarks

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

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

GatewayInfo Event (MQTTSN Control)

Fired when the control receives a GWINFO or ADVERTISE packet.

Syntax

Sub mqttsncontrol_GatewayInfo(MessageType As String, GatewayId As Integer, GatewayAddress As String, Interval As Integer)

Remarks

This event allows packets containing gateway information to be processed. These packets could be received from regular gateway advertisements or gateway info requests from this or other clients. This gateway information is used to manage the client's list of active gateways.

The value of MessageType could be GWINFO or ADVERTISE.

GatewayAddress will be in format host:port.

If the gateway address field is not present in the received GWINFO packet, GatewayAddress will use the packet source IP address.

This functionality is not yet implemented.

Log Event (MQTTSN Control)

Fires once for each log message.

Syntax

Sub mqttsncontrol_Log(LogLevel As Integer, Message As String, LogType As String)

Remarks

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

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

0 (None) No events are logged.
1 (Info - default) Informational events are logged.
2 (Verbose) Detailed data is logged.
3 (Debug) Debug data is logged.

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

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

MessageIn Event (MQTTSN Control)

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

Syntax

Sub mqttsncontrol_MessageIn(MsgId As Integer, TopicId As String, TopicIdType As Integer, QOS As Integer, Message As String, Retained As Boolean, Duplicate As Boolean, ReturnCode As Integer)

Remarks

Fired on reception of a PUBLISH packet for QoS 0 and 1 messages, and reception of a PUBREL packet for QoS 2 messages.

  • MsgId: a unique (among currently unacknowledged incoming messages) identifier attached to messages of QoS 1 and 2. Otherwise value will be 0.
  • TopicId: topic id of type TopicIdType.
  • TopicIdType: 0 = registered topic id, 1 = pre-defined topic id, 2 = short topic name.
  • 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.
  • ReturnCode: QoS 1 messages can be accepted or rejected by setting the ReturnCode to a value listed below.
    • 0: accepted
    • 1: rejected - congestion
    • 2: rejected - invalid topic id
    • 3: rejected - not supported

Inbound Message Processing

Incoming messages with a QoS of 1 follow these steps:

  1. The TopicInfo event is fired (if the gateway sends a REGISTER packet because it needs to inform the client name and assigned topic id it will use in a PUBLISH message).
  2. The control sends a REGACK (register acknowledgment) packet in response (if a REGISTER packet was received).
  3. The MessageIn event is fired.
  4. The control sends a PUBACK (publish acknowledgment) packet in response (with the return code from the MessageIn event if one is set).

Incoming messages with a QoS of 2 follow these steps:

  1. The TopicInfo event is fired (if the gateway sends a REGISTER packet because it needs to inform the client name and assigned topic id it will use in a PUBLISH message).
  2. The control sends a REGACK (register acknowledgment) packet in response (if a REGISTER packet was received).
  3. The control sends a PUBREC (publish received) packet in response.
  4. The control waits to receive a PUBREL (publish release) packet.
  5. The control sends a PUBCOMP (publish complete) packet in response.
  6. The MessageIn event is fired.

TopicInfo Event (MQTTSN Control)

Fired when the client receives a REGISTER packet from the gateway assigning a topic id to a topic name.

Syntax

Sub mqttsncontrol_TopicInfo(TopicId As Integer, TopicName As String, ReturnCode As Integer)

Remarks

A gateway sends a REGISTER packet to a client if it wants to inform that client about the topic name and the assigned topic id that it will use later on when sending PUBLISH messages of the corresponding topic name. The client must establish a new topic id mapping to the topic name indicated.

This happens for example when the client connects without starting a clean session or the client has subscribed to topic names that contain wildcard characters.

When a REGISTER packet is received, the control will respond with a REGACK packet. To set the value of the return code contained in the packet, set it to one of the below values.

  • 0: accepted
  • 1: rejected - congestion
  • 2: rejected - invalid topic id
  • 3: rejected - not supported

When a client subscribes to a topic with wildcard characters, the specific topic names it will receive messages on have not yet been registered to topic ids, so the first step in receiving such messages is the REGISTER packet. It can then receive incoming messages with that id. See MessageIn for more.

Config Settings (MQTTSN Control)

The control accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, access to these internal properties is provided through the Config method.

MQTTSN Config Settings

ConnectionTimeout:   How long to wait for a connection attempt to succeed.

This setting controls how long the control will wait, in seconds, for connection attempt to succeed before timing out. The default is 60 seconds.

Duplicate:   Whether to set the Duplicate flag when publishing a message.

When enabled, the component will set the Duplicate flag when a message is published using PublishData or PublishMessage. See those methods for details on retransmission.

LogLevel:   The level of detail that is logged.

This setting controls the level of detail that is logged through the Log event. Possible values are:

0 (None) No events are logged.
1 (Info - default) Informational events are logged.
2 (Verbose) Detailed data is logged.
3 (Debug) Debug data is logged.

PingTimeout:   Length of time to wait for a PINGRESP packet.

This setting controls how long the control will wait, in seconds, for a response to a ping message before timing out. The default is 5 seconds.

Retain:   Whether to set the Retain flag when publishing a message.

When enabled, the control will set the Retain flag when a message is published using PublishData or PublishMessage. By default, this is disabled.

Publishing a non-empty message with the Retain flag set and a non-zero QoS will cause the server to store it (replacing any previously retained message in the process) so that it can be delivered to any clients which subscribe to the topic in the future. (If the QoS is 0, the server can store the message, but it is not required to do so indefinitely, if at all.)

If the control publishes an empty message with the Retain flag set, then (regardless of its QoS) the server will remove any previously retained message for the topic.

Note that messages with the Retain flag set are still processed by the server and delivered as usual to clients currently subscribed to the topic, regardless of whether they are empty or not. Also note that retained messages are not part of a session's state, they are retained until they are either removed or replaced by another retained message, regardless of whether or not the client connected with CleanSession set to True.

SubscribedTopicId:   Topic id assigned by the gateway when a topic name is used in a SUBSCRIBE message.

When the client uses a TopicIdType of 0 (topic name), this name must be registered to a topic id. In this scenario, the topic id assigned will be included in the SUBACK message and will be set here when it is received.

See Subscribe for more details.

SubscribeDUP:   Whether to set the Duplicate flag when subscribe to a topic.

When enabled, the component will set the Duplicate flag when Subscribe is called. See that method for details on retransmission.

WillQOS:   The QoS value to use for the Will message.

If WillTopic is set to a non-empty string when Connect is called, this is the QoS value that will be used for the Will message; possible values are 0 (default), 1, and 2. (Note that this setting is ignored if WillTopic is empty.)

Refer to WillTopic for more information.

WillRetain:   Whether the server should retain the Will message after publishing it.

If WillTopic is set to a non-empty string when Connect is called, this determines whether or not the server will treat the Will message as retained. By default, this is disabled. (Note that this setting is ignored if WillTopic is empty.)

See Retain for general information about how retained messages are handled by the server.

Refer to WillTopic for more information.

Base Config Settings

CodePage:   The system code page used for Unicode to Multibyte translations.

The default code page is Unicode UTF-8 (65001).

The following is a list of valid code page identifiers:

IdentifierName
037IBM EBCDIC - U.S./Canada
437OEM - United States
500IBM EBCDIC - International
708Arabic - ASMO 708
709Arabic - ASMO 449+, BCON V4
710Arabic - Transparent Arabic
720Arabic - Transparent ASMO
737OEM - Greek (formerly 437G)
775OEM - Baltic
850OEM - Multilingual Latin I
852OEM - Latin II
855OEM - Cyrillic (primarily Russian)
857OEM - Turkish
858OEM - Multilingual Latin I + Euro symbol
860OEM - Portuguese
861OEM - Icelandic
862OEM - Hebrew
863OEM - Canadian-French
864OEM - Arabic
865OEM - Nordic
866OEM - Russian
869OEM - Modern Greek
870IBM EBCDIC - Multilingual/ROECE (Latin-2)
874ANSI/OEM - Thai (same as 28605, ISO 8859-15)
875IBM EBCDIC - Modern Greek
932ANSI/OEM - Japanese, Shift-JIS
936ANSI/OEM - Simplified Chinese (PRC, Singapore)
949ANSI/OEM - Korean (Unified Hangul Code)
950ANSI/OEM - Traditional Chinese (Taiwan; Hong Kong SAR, PRC)
1026IBM EBCDIC - Turkish (Latin-5)
1047IBM EBCDIC - Latin 1/Open System
1140IBM EBCDIC - U.S./Canada (037 + Euro symbol)
1141IBM EBCDIC - Germany (20273 + Euro symbol)
1142IBM EBCDIC - Denmark/Norway (20277 + Euro symbol)
1143IBM EBCDIC - Finland/Sweden (20278 + Euro symbol)
1144IBM EBCDIC - Italy (20280 + Euro symbol)
1145IBM EBCDIC - Latin America/Spain (20284 + Euro symbol)
1146IBM EBCDIC - United Kingdom (20285 + Euro symbol)
1147IBM EBCDIC - France (20297 + Euro symbol)
1148IBM EBCDIC - International (500 + Euro symbol)
1149IBM EBCDIC - Icelandic (20871 + Euro symbol)
1200Unicode UCS-2 Little-Endian (BMP of ISO 10646)
1201Unicode UCS-2 Big-Endian
1250ANSI - Central European
1251ANSI - Cyrillic
1252ANSI - Latin I
1253ANSI - Greek
1254ANSI - Turkish
1255ANSI - Hebrew
1256ANSI - Arabic
1257ANSI - Baltic
1258ANSI/OEM - Vietnamese
1361Korean (Johab)
10000MAC - Roman
10001MAC - Japanese
10002MAC - Traditional Chinese (Big5)
10003MAC - Korean
10004MAC - Arabic
10005MAC - Hebrew
10006MAC - Greek I
10007MAC - Cyrillic
10008MAC - Simplified Chinese (GB 2312)
10010MAC - Romania
10017MAC - Ukraine
10021MAC - Thai
10029MAC - Latin II
10079MAC - Icelandic
10081MAC - Turkish
10082MAC - Croatia
12000Unicode UCS-4 Little-Endian
12001Unicode UCS-4 Big-Endian
20000CNS - Taiwan
20001TCA - Taiwan
20002Eten - Taiwan
20003IBM5550 - Taiwan
20004TeleText - Taiwan
20005Wang - Taiwan
20105IA5 IRV International Alphabet No. 5 (7-bit)
20106IA5 German (7-bit)
20107IA5 Swedish (7-bit)
20108IA5 Norwegian (7-bit)
20127US-ASCII (7-bit)
20261T.61
20269ISO 6937 Non-Spacing Accent
20273IBM EBCDIC - Germany
20277IBM EBCDIC - Denmark/Norway
20278IBM EBCDIC - Finland/Sweden
20280IBM EBCDIC - Italy
20284IBM EBCDIC - Latin America/Spain
20285IBM EBCDIC - United Kingdom
20290IBM EBCDIC - Japanese Katakana Extended
20297IBM EBCDIC - France
20420IBM EBCDIC - Arabic
20423IBM EBCDIC - Greek
20424IBM EBCDIC - Hebrew
20833IBM EBCDIC - Korean Extended
20838IBM EBCDIC - Thai
20866Russian - KOI8-R
20871IBM EBCDIC - Icelandic
20880IBM EBCDIC - Cyrillic (Russian)
20905IBM EBCDIC - Turkish
20924IBM EBCDIC - Latin-1/Open System (1047 + Euro symbol)
20932JIS X 0208-1990 & 0121-1990
20936Simplified Chinese (GB2312)
21025IBM EBCDIC - Cyrillic (Serbian, Bulgarian)
21027Extended Alpha Lowercase
21866Ukrainian (KOI8-U)
28591ISO 8859-1 Latin I
28592ISO 8859-2 Central Europe
28593ISO 8859-3 Latin 3
28594ISO 8859-4 Baltic
28595ISO 8859-5 Cyrillic
28596ISO 8859-6 Arabic
28597ISO 8859-7 Greek
28598ISO 8859-8 Hebrew
28599ISO 8859-9 Latin 5
28605ISO 8859-15 Latin 9
29001Europa 3
38598ISO 8859-8 Hebrew
50220ISO 2022 Japanese with no halfwidth Katakana
50221ISO 2022 Japanese with halfwidth Katakana
50222ISO 2022 Japanese JIS X 0201-1989
50225ISO 2022 Korean
50227ISO 2022 Simplified Chinese
50229ISO 2022 Traditional Chinese
50930Japanese (Katakana) Extended
50931US/Canada and Japanese
50933Korean Extended and Korean
50935Simplified Chinese Extended and Simplified Chinese
50936Simplified Chinese
50937US/Canada and Traditional Chinese
50939Japanese (Latin) Extended and Japanese
51932EUC - Japanese
51936EUC - Simplified Chinese
51949EUC - Korean
51950EUC - Traditional Chinese
52936HZ-GB2312 Simplified Chinese
54936Windows XP: GB18030 Simplified Chinese (4 Byte)
57002ISCII Devanagari
57003ISCII Bengali
57004ISCII Tamil
57005ISCII Telugu
57006ISCII Assamese
57007ISCII Oriya
57008ISCII Kannada
57009ISCII Malayalam
57010ISCII Gujarati
57011ISCII Punjabi
65000Unicode UTF-7
65001Unicode UTF-8

The following is a list of valid code page identifiers for Mac OS only:

IdentifierName
1ASCII
2NEXTSTEP
3JapaneseEUC
4UTF8
5ISOLatin1
6Symbol
7NonLossyASCII
8ShiftJIS
9ISOLatin2
10Unicode
11WindowsCP1251
12WindowsCP1252
13WindowsCP1253
14WindowsCP1254
15WindowsCP1250
21ISO2022JP
30MacOSRoman
10UTF16String
0x90000100UTF16BigEndian
0x94000100UTF16LittleEndian
0x8c000100UTF32String
0x98000100UTF32BigEndian
0x9c000100UTF32LittleEndian
65536Proprietary

UseInternalSecurityAPI:   Tells the control whether or not to use the system security libraries or an internal implementation.

By default the control will use the system security libraries to perform cryptographic functions where applicable. Setting this to tells the control to use the internal implementation instead of using the system's security API.

Trappable Errors (MQTTSN Control)

UDP Errors

20105    UDP is already Active.
20107    You cannot change the LocalPort while the control is Active.
20108    You cannot change the LocalHost at this time. A connection is in progress.
20110    The control must be Active for this operation.
20113    Cannot change MaxPacketSize while the control is Active.
20114    Cannot change ShareLocalPort option while the control is Active.
20115    Cannot change RemoteHost when UseConnection is set and the control Active.
20116    Cannot change RemotePort when UseConnection is set and the control is Active.
20117    RemotePort can't be zero when UseConnection is set. Please specify a valid service port number.
20118    Cannot change UseConnection while the control is Active.
20119    Message can't be longer than MaxPacketSize.
20120    Message too short.
20435    Unable to convert string to selected CodePage

SSL Errors

20271    Cannot load specified security library.
20272    Cannot open certificate store.
20273    Cannot find specified certificate.
20274    Cannot acquire security credentials.
20275    Cannot find certificate chain.
20276    Cannot verify certificate chain.
20277    Error during handshake.
20281    Error verifying certificate.
20282    Could not find client certificate.
20283    Could not find server certificate.
20284    Error encrypting data.
20285    Error decrypting data.

TCP/IP Errors

25005    [10004] Interrupted system call.
25010    [10009] Bad file number.
25014    [10013] Access denied.
25015    [10014] Bad address.
25023    [10022] Invalid argument.
25025    [10024] Too many open files.
25036    [10035] Operation would block.
25037    [10036] Operation now in progress.
25038    [10037] Operation already in progress.
25039    [10038] Socket operation on non-socket.
25040    [10039] Destination address required.
25041    [10040] Message too long.
25042    [10041] Protocol wrong type for socket.
25043    [10042] Bad protocol option.
25044    [10043] Protocol not supported.
25045    [10044] Socket type not supported.
25046    [10045] Operation not supported on socket.
25047    [10046] Protocol family not supported.
25048    [10047] Address family not supported by protocol family.
25049    [10048] Address already in use.
25050    [10049] Can't assign requested address.
25051    [10050] Network is down.
25052    [10051] Network is unreachable.
25053    [10052] Net dropped connection or reset.
25054    [10053] Software caused connection abort.
25055    [10054] Connection reset by peer.
25056    [10055] No buffer space available.
25057    [10056] Socket is already connected.
25058    [10057] Socket is not connected.
25059    [10058] Can't send after socket shutdown.
25060    [10059] Too many references, can't splice.
25061    [10060] Connection timed out.
25062    [10061] Connection refused.
25063    [10062] Too many levels of symbolic links.
25064    [10063] File name too long.
25065    [10064] Host is down.
25066    [10065] No route to host.
25067    [10066] Directory not empty
25068    [10067] Too many processes.
25069    [10068] Too many users.
25070    [10069] Disc Quota Exceeded.
25071    [10070] Stale NFS file handle.
25072    [10071] Too many levels of remote in path.
25092    [10091] Network subsystem is unavailable.
25093    [10092] WINSOCK DLL Version out of range.
25094    [10093] Winsock not loaded yet.
26002    [11001] Host not found.
26003    [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
26004    [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
26005    [11004] Valid name, no data record (check DNS setup).

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IPWorks IoT 2022 ActiveX Edition - Version 22.0 [Build 8369]