When enabled, the task will automatically attempt to reconnect to the server if the connection is interrupted due to a connection error. This behavior is disabled by default.

The client uses this value to limit the number of aliases it is willing to hold on this connection. A value of 0 (default) indicates that the client does not accept any topic aliases on this connection.

This value is sent to the server in the CONNECT packet. It is also available in the ConnectProperties config. See the TopicAlias config for more details.

Valid only for MQTT 5.

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

The values listed below are available. If a value is absent in the CONNECT packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the CONNECT packet (after it has previously been set), set it to "", or -1 for integers. To reset all ConnectProperties values, set the config JSON string to "".

To set these values, set the ConnectProperties config to a string JSON object containing one or more key/value pairs to set. For example, to set all values: { "ClientTopicAliasMax":"20", "MaximumPacketSize":"128000", "ReceiveMaximum":"12", "RequestResponseInformation":"false", "RequestProblemInformation":"true", "SessionExpInterval":"1234" }

Valid only for MQTT 5.

This property contains properties to be sent by the client in the DISCONNECT packet, or is set when the client receives a DISCONNECT packet from the server.

Supported properties are:

To reset an individual value so that it is no longer included in the DISCONNECT packet (after it has previously been set), set it to "", or -1 for integers. To reset all DisconnectProperties values, set the config JSON string to "".

Valid only for MQTT 5.

Either the client or server may set a reason code before disconnecting to be included in the DISCONNECT packet.

This value will be populated when the task receives a DISCONNECT packet from the server.

For a full list of values applicable to be sent by the client, server or both, see the MQTT 5 specification. They include:

• 0x00: Normal disconnection - Close the connection normally. Do not send the Will Message.
• 0x04: Disconnect with Will Message (Client only) - The Client wishes to disconnect but requires that the Server also publishes its Will Message.
• 0x80: Unspecified error - The Connection is closed but the sender either does not wish to reveal the reason, or none of the other Reason Codes apply.

Valid only for MQTT 5.

When enabled, the task will set the Duplicate flag when a message is published using PublishData or PublishMessage. By default, this is disabled; and manually enabling it is not recommended. Prefer instead to let the task handle republishing packets, which it will do automatically so long as RepublishInterval is set to a non-zero value (default).

This setting is ignored when messages are published with a QoS of 0.

Note: The Duplicate flag in an MQTT PUBLISH packet refers to the Id of the packet, not the message itself. According to the MQTT specification, it is possible (and perfectly legal) that a client could receive two QoS 1 PUBLISH packets with different Ids despite having the exact same message data.

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

The values listed below are available. If a value is absent in the PUBLISH packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the PUBLISH packet (after it has previously been set), set it to "", or -1 for integers. To reset all OutgoingMessageProperties values, set the config JSON string to "".

To set these values, set the OutgoingMessageProperties config to a string JSON object containing one or more key/value pairs to set. For example: { "ContentType":"plain/text", "CorrelationData":"00000000", "MessageExpInterval":"1000", "PayloadFormatIndicator":"1", "ResponseTopic": "ResponseTopic", "TopicAlias":"1", "UserProperty":"prp1:val1", "UserProperty":"prp2:val2" } Valid only for MQTT 5.

In MQTT 3.1.1 this setting determines how long the task will wait to receive a PUBACK (QoS 1) or PUBREC (QoS 2) for an outgoing message before republishing it. Republished messages will automatically use the same packet Id and have their Duplicate flag set.

The default RepublishInterval is 60 seconds. Specify a RepublishInterval of 0 to prevent the task from automatically republishing messages.

In MQTT 5, messages are only republished if the client is disconnected before receiving a PUBACK or PUBREC. This property is only valid for MQTT 3.1.1.

The receiver of a message with a Response Topic sends a response by using the Response Topic as the Topic Name of a PUBLISH. If the Request Message contains a Correlation Data, the receiver of the Request Message should also include this Correlation Data as a property in the PUBLISH packet of the Response Message.

To send a Request Message, set this value before calling PublishMessage.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to "".

ResponseTopic and Correlation Data are also accessible in the OutgoingMessageProperties config.

Valid only for MQTT 5.

When enabled, the task 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 task 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.

Setting this setting to a string with hex bytes will cause the task to construct and send a custom packet. This should not be necessary except for debugging purposes.

If 0 (default), the session ends on disconnection. If 0xFFFFFFFF, the session does not expire.

The server may override this value. Additionally, the client may send a new value in the DisconnectProperties (as long as it was not 0 originally).

See CleanSession for more details on stored sessions in MQTT 5. This property also available in ConnectProperties.

Valid only for MQTT 5.

This can be set to a valid file path before calling SaveSession or RestoreSession to have the task automatically save and restore the session state data to and from a file.

To instruct the server to establish a subscription identifier mapping and return this value with any future PUBLISH packets for a topic filter, set this config before calling Subscribe for the desired topic.

Note that this value applies only to SUBSCRIBE packets and not to outgoing or incoming messages. The client is not permitted to send a PUBLISH packet with a subscription id - the server will include it when it sends PUBLISH packets to subscribing clients if those clients have established ids. To access subscription ids of incoming messages, see the "SubscriptionIdentifiers" field in the MQTTMessage type.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to -1.

Valid only for MQTT 5.

To establish a topic alias mapping, set this to a unique value before calling PublishMessage with the desired topic filter. Then, next time the client publishes a message to this topic, it may set TopicAlias to the value established and call PublishMessage with an empty topic filter string. The message will be published to the proper topic without sending the topic filter.

A sender can modify the Topic Alias mapping by sending another PUBLISH in the same Network Connection with the same Topic Alias value and a different non-zero length Topic Name.

Note that a topic alias must have a value greater than zero and less than or equal to the maximum supported by the server. Topic alias mappings exist only within a connection and are not a part of stored session state data. The Topic Alias mappings used by the Client and Server are independent from each other.

To reset the value once it has been previously set, so that it is no longer included in future packets, set it to -1.

Also accessible in the OutgoingMessageProperties config.

Valid only for MQTT 5.

When the Subscribe and Unsubscribe methods are called, the task parses the topic filters string passed to them into a list of topic filters by splitting it, using this setting's current value as the delimiter. By default, this is set to ,.

The value of this config should be a comma-separated list of boolean values.

For topic filters subscribed to with a True flag, messages will not be forwarded to the same ClientId they were published from.

By default, this value is empty and all flags are False.

Valid only for MQTT 5.

This can be set to a comma-separated list of individual QoS values to use for each topic filter passed to the Subscribe method, causing the task to ignore the QoS value passed to Subscribe. When doing this, the number of QoS values set to this setting must match the number of topic filters passed to Subscribe.

If this setting is set to the empty string (default) when Subscribe is called with multiple topic filters, the task will use the QoS value passed to Subscribe for all of them.

The value of this config should be a comma-separated list of boolean values.

For topic filters subscribed to with a True flag, messages forwarded for this subscription will keep the retain flag they were published with (as opposed to always being set to False).

By default, this value is empty and all flags are False.

Valid only for MQTT 5.

The value of this config should be a comma-separated list of integer values specifying 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

By default, this value is empty and all values are 0.

Valid only for MQTT 5.

The values listed below are available. If a value is absent in the CONNECT packet, the server will treat its value as the default listed.

To reset an individual value so that it is no longer included in the CONNECT packet (after it has previously been set), set it to "", or -1 for integers. To reset all WillProperties values, set the config JSON string to "".

Note that these values will be ignored if WillTopic is empty.

To set these values, set the ConnectProperties config to a string JSON object containing one or more key/value pairs to set. For example, to set all values: { "ContentType":"text/plain", "CorrelationData":"00000000", "MessageExpInterval":"3600", "PayloadFormatIndicator":"1", "ResponseTopic": "ResponseTopic", "WillDelayInterval":"10" }

Valid only for MQTT 5.

If WillTopic is set to a non-empty string 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.

If WillTopic is set to a non-empty string 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.

If set to true, the task will reuse the context if and only if the following criteria are met:

• The target host name is the same.
• The system cache entry has not expired (default timeout is 10 hours).
• The application process that calls the function is the same.
• The logon session is the same.
• The instance of the task is the same.

This minimum cipher strength largely dependent on the security modules installed on the system. If the cipher strength specified is not supported, an error will be returned when connections are initiated.

Please note that this setting contains the minimum cipher strength requested from the security library.

Use this setting with caution. Requesting a lower cipher strength than necessary could potentially cause serious security vulnerabilities in your application.

The enabled cipher suites to be used in SSL negotiation.

By default, the enabled cipher suites will include all available ciphers ("*").

The special value "*" means that the task will pick all of the supported cipher suites. If SSLEnabledCipherSuites is set to any other value, only the specified cipher suites will be considered.

Multiple cipher suites are separated by semicolons.

Example values when UseInternalSecurityAPI is False (default): // The "Other" property could contain ONE of the following lines: SSLEnabledCipherSuites=* SSLEnabledCipherSuites=CALG_AES_256 SSLEnabledCipherSuites=CALG_AES_256;CALG_3DES Possible values when UseInternalSecurityAPI is False (default) include:

• CALG_3DES
• CALG_3DES_112
• CALG_AES
• CALG_AES_128
• CALG_AES_192
• CALG_AES_256
• CALG_AGREEDKEY_ANY
• CALG_CYLINK_MEK
• CALG_DES
• CALG_DESX
• CALG_DH_EPHEM
• CALG_DH_SF
• CALG_DSS_SIGN
• CALG_ECDH
• CALG_ECDH_EPHEM
• CALG_ECDSA
• CALG_ECMQV
• CALG_HASH_REPLACE_OWF
• CALG_HUGHES_MD5
• CALG_HMAC
• CALG_KEA_KEYX
• CALG_MAC
• CALG_MD2
• CALG_MD4
• CALG_MD5
• CALG_NO_SIGN
• CALG_OID_INFO_CNG_ONLY
• CALG_OID_INFO_PARAMETERS
• CALG_PCT1_MASTER
• CALG_RC2
• CALG_RC4
• CALG_RC5
• CALG_RSA_KEYX
• CALG_RSA_SIGN
• CALG_SCHANNEL_ENC_KEY
• CALG_SCHANNEL_MAC_KEY
• CALG_SCHANNEL_MASTER_HASH
• CALG_SEAL
• CALG_SHA
• CALG_SHA1
• CALG_SHA_256
• CALG_SHA_384
• CALG_SHA_512
• CALG_SKIPJACK
• CALG_SSL2_MASTER
• CALG_SSL3_MASTER
• CALG_SSL3_SHAMD5
• CALG_TEK
• CALG_TLS1_MASTER
• CALG_TLS1PRF

• TLS_DHE_DSS_WITH_AES_128_GCM_SHA256
• TLS_DHE_DSS_WITH_AES_256_GCM_SHA384
• TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
• TLS_DHE_DSS_WITH_AES_128_CBC_SHA
• TLS_DHE_DSS_WITH_AES_128_CBC_SHA256
• TLS_DHE_DSS_WITH_AES_256_CBC_SHA
• TLS_DHE_DSS_WITH_AES_256_CBC_SHA256
• TLS_DHE_DSS_WITH_DES_CBC_SHA
• TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
• TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
• TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
• TLS_DHE_RSA_WITH_AES_128_CBC_SHA
• TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
• TLS_DHE_RSA_WITH_AES_256_CBC_SHA
• TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
• TLS_DHE_RSA_WITH_DES_CBC_SHA
• TLS_RSA_WITH_AES_256_GCM_SHA384
• TLS_RSA_WITH_AES_128_GCM_SHA256
• TLS_RSA_WITH_3DES_EDE_CBC_SHA
• TLS_RSA_WITH_AES_128_CBC_SHA
• TLS_RSA_WITH_AES_128_CBC_SHA256
• TLS_RSA_WITH_AES_256_CBC_SHA
• TLS_RSA_WITH_AES_256_CBC_SHA256
• TLS_RSA_WITH_DES_CBC_SHA
• TLS_RSA_WITH_RC4_128_MD5
• TLS_RSA_WITH_RC4_128_SHA

If SSLEnabledProtocols is configured to use TLS 1.3 the following values are supported:

• TLS_AES_128_GCM_SHA256
• TLS_AES_256_GCM_SHA384

SSLEnabledCipherSuites is used together with SSLCipherStrength.

Used to enable/disable the supported security protocols.

Not all supported protocols are enabled by default (the value of this setting is 4032). If you want more granular control over the enabled protocols, you can set this property to the binary 'OR' of one or more of the following values:

Note: TLS 1.1 and TLS1.2 support are only available starting with Windows 7.

Note: Enabling TLS 1.3 will automatically set UseInternalSecurityAPI to True.

This setting specifies whether the transport log contains the full certificate chain. By default this value is False and only the leaf certificate will be present.

If set to True all certificates returned by the server will be present in the transport log. This includes the leaf certificate, any intermediate certificate, and the root certificate.

Note: When UseInternalSecurityAPI is set to True this value is automatically set to True. This is needed for proper validation when using the internal provider.

The following flags are defined (specified in hexadecimal notation). They can be or-ed together to exclude multiple conditions:

This setting specifies the allowed server certificate signature algorithms when UseInternalSecurityAPI is True and SSLEnabledProtocols is set to allow TLS 1.2.

When specified the task will verify that the server certificate signature algorithm is among the values specified in this setting. If the server certificate signature algorithm is unsupported the task will fail with an error.

The format of this value is a comma separated list of hash-signature combinations. For instance: // The "Other" could contain ALL of these lines: UseInternalSecurityAPI=true SSLEnabledProtocols=3072 TLS12SignatureAlgorithms=sha1-rsa,sha1-dsa,sha256-rsa,sha256-dsa The default value for this setting is "sha1-rsa,sha1-dsa,sha224-rsa,sha224-dsa,sha256-rsa,sha256-dsa,sha384-rsa,sha384-dsa,sha512-rsa,sha512-dsa".

In order to not restrict the server's certificate signature algorithm, specify an empty string as the value for this setting, which will cause the signature_algorithms TLS 1.2 extension to not be sent.

This setting specifies a comma separated list of named groups used in TLS 1.2 for ECC.

The default value is ecdhe_secp256r1,ecdhe_secp384r1,ecdhe_secp521r1.

When using TLS 1.2 and UseInternalSecurityAPI is set to True, the values refer to the supported groups for ECC. The following values are supported:

• "ecdhe_secp256r1" (default)
• "ecdhe_secp384r1" (default)
• "ecdhe_secp521r1" (default)

This setting specifies a comma separated list of named groups used in TLS 1.3 for key exchange. The groups specified here will have key share data pregenerated locally before establishing a connection. This can prevent an additional round trip during the handshake if the group is supported by the server.

The default value is set to balance common supported groups and the computational resources required to generate key shares. As a result only some groups are included by default in this setting.

Note: All supported groups can always be used during the handshake even if not listed here, but if a group is used which is not present in this list it will incur an additional round trip and time to generate the key share for that group.

In most cases this setting does not need to be modified. This should only be modified if there is a specific reason to do so.

The default value is ecdhe_x25519,ecdhe_secp256r1,ecdhe_secp384r1,ffdhe_2048,ffdhe_3072

The values are ordered from most preferred to least preferred. The following values are supported:

• "ecdhe_x25519" (default)
• "ecdhe_x448"
• "ecdhe_secp256r1" (default)
• "ecdhe_secp384r1" (default)
• "ecdhe_secp521r1"
• "ffdhe_2048" (default)
• "ffdhe_3072" (default)
• "ffdhe_4096"
• "ffdhe_6144"
• "ffdhe_8192"

This setting holds a comma separated list of allowed signature algorithms. Possible values are:

• "rsa_pkcs1_sha256" (default)
• "rsa_pkcs1_sha384" (default)
• "rsa_pkcs1_sha512" (default)

This setting specifies a comma separated list of named groups used in TLS 1.3 for key exchange. This setting should only be modified if there is a specific reason to do so.

The default value is ecdhe_x25519,ecdhe_x448,ecdhe_secp256r1,ecdhe_secp384r1,ecdhe_secp521r1,ffdhe_2048,ffdhe_3072,ffdhe_4096,ffdhe_6144,ffdhe_8192

The values are ordered from most preferred to least preferred. The following values are supported:

• "ecdhe_x25519" (default)
• "ecdhe_x448" (default)
• "ecdhe_secp256r1" (default)
• "ecdhe_secp384r1" (default)
• "ecdhe_secp521r1" (default)
• "ffdhe_2048" (default)
• "ffdhe_3072" (default)
• "ffdhe_4096" (default)
• "ffdhe_6144" (default)
• "ffdhe_8192" (default)

If AbsoluteTimeout is set to True, any method which does not complete within Timeout seconds will be aborted. By default, AbsoluteTimeout is False, and the timeout is an inactivity timeout.

The LocalHost configuration 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 multihomed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the task initiate connections (or accept in the case of server tasks) only through that interface.

If the task is connected, the LocalHost configuration 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 multihomed hosts (machines with more than one IP interface).

When set to True, the socket will send all data that are ready to send at once. When set to False, the socket will send smaller buffered packets of data at small intervals. This is known as the Nagle algorithm.

By default, this configuration setting is set to False.

When set to False, the task will use the system security libraries by default to perform cryptographic functions where applicable. In this case, calls to unmanaged code will be made. In certain environments, this is not desirable. To use a completely managed security implementation, set this setting to True.

Setting this configuration setting to True tells the task to use the internal implementation instead of using the system security libraries.

On Windows, this setting is set to False by default. On Linux/macOS, this setting is set to True by default.

If using the .NET Standard Library, this setting will be True on all platforms. The .NET Standard library does not support using the system security libraries.

Note: This setting is static. The value set is applicable to all tasks used in the application.

When this value is set, the product's system dynamic link library (DLL) is no longer required as a reference, as all unmanaged code is stored in that file.