Item

Description

Publish Payload Format

Selects one of several built-in payload formats for publishing.

Note: Client devices must to be configured to listen for payloads with a matching format.

The payload can be set to include data from a single tag or multiple tags:

• Single: each payload contains data for only a single tag

• Multi: each payload can contain data from multiple tags

Each format type uses a separate JSON object to store each tag’s data. This “tag value object” can embedded within the payload structure in different ways:

• No Wrap: The payload root object is the tag value object, and all tag properties are direct children of the root object. Only available for “Single” payloads.

  • Example: {"Value": 1}

• Wrap: Uses the tag ID as the property name for the value object. Available for both “Single” and “Multi” payloads.

  • Example: {"tag1": {"Value": 1}, "tag2": {"Value": 2}}

• Array Wrap: Stores an array of tag value objects named "Tags". The tag ID property is included in the tag value object.

  • Example: {"Tags": [{"ID": "tag1, "Value": 1}, {"ID": "tag2", "Value": 123.456}]}

There are also two pre-made payload options: “Basic” and “Full”:

• Basic: Includes the following properties:

  • "Value": the tag's value

  • "Value Time": a 64-bit integer timestamp

Publish QOS

Choose the Quality of Service to use when publishing. Determines how many times each message will be sent in the event of packet loss.

• 0: The message will be sent at most once.

• 1: The message will be sent at least once (but may be sent multiple times).

• 2: The message will be sent exactly once.

In general, a higher value means the data will be more accurate, but this will also require more handshakes and bandwidth consumption.

Publish Retain Messages

When enabled, the last known value for each topic will be retained by the broker. When a new client subscribes to a topic, the retained value will be published to the client by the broker. The broker will only retain up to one value per topic.

Publish Topic Prefix

Sets a prefix string to include in all publish topics. Note that this does not automatically add a / level separator to the full topic.

For example, with a prefix of prefix and a tag named New Tag, the default topic will be prefixNew Tag.

Publish Topic Suffix

Sets a suffix string to include in all publish topics. Note that this does not automatically add a / level separator to the full topic.

For example, with a suffix of suffix and a tag named New Tag, the default topic will be New Tagsuffix.

Access Type

The MQTT JSON Publisher server device always publishes MQTT messages when a hosted tag’s value updates. This setting lets you choose whether the device also subscribes to MQTT messages from clients.

• Publish/Subscribe: Subscribes to messages from other MQTT clients and updates the hosted tag’s value when a message is received. This allows the MQTT JSON Publisher device to act as a client.

• Publish Only: Ignores messages from MQTT clients. This effectively makes the tags read-only to other clients.

Subscribe Payload Format

Selects one of several built-in payload formats for subscribing.

Note: This property only changes the expected payload format for subscribing. Client devices must be configured to publish payloads use a matching format. Any subscribed messages and properties that do not match the specified format will be ignored.

The payload can be set to include data from a single tag or multiple tags:

• Single: Each payload contains data for only a single tag

• Multi: Each payload can contain data from multiple tags

Each format type uses a separate JSON object to store each tag’s data. This “tag value object” can embedded within the payload structure in different ways:

• No Wrap: The payload root object is the tag value object, and all tag properties are direct children of the root object. Only available for “Single” payloads.

  • Example: {"Value": 1}

• Wrap: Uses the tag ID as the property name for the value object. Available for both “Single” and “Multi” payloads.

  • Example: {"tag1": {"Value": 1}, "tag2": {"Value": 2}}

• Array Wrap: Stores an array of tag value objects named "Tags". The tag ID property is included in the tag value object.

  • Example: {"Tags": [{"ID": "tag1, "Value": 1}, {"ID": "tag2", "Value": 123.456}]}

There are also two pre-made payload options which allow you to specify which properties to include: “Basic” and “Full”.

• Basic: Includes the following properties:

  • "Value": The tag's value

  • "Value Time": A datetime string for when the tag value was updated by the host device.

• Full: Includes all of the “Basic” properties, as well as the following properties:

  • “Type”"Type": the tag’s tag's data type. This will be one of :("boolean" (BOOL)

    , "float" (FLOAT32)

    , "double" (FLOAT64)

    , "byte" (INT8)

    , "short" (INT16)

    , "int" (INT32)

    , "long" (INT64)

    , "unsignedByte" (UINT8)

    , "unsignedShort" (UINT16)

    , "unsignedInt" (UINT32)

    , "unsignedLong" (UINT64)

    , or "string" (STRING))

  • "Read Time": A datetime string for when the tag value was last read.

  • "Device": The client I/O device of the tag.

  • "Quality": The quality of the tag. One of “Active” or “

Note: All datetime strings use the format “yyyy-MM-ddTHH:mm:ss”.

Subscribe QOS

Choose the Quality of Service to use when subscribing. Determines how many times each message will be sent in the event of packet loss.

• 0: The message will be sent at most once.

• 1: The message will be sent at least once (but may be sent multiple times).

• 2: The message will be sent exactly once.

In general, a higher value means communication will be more reliable, but also requires more handshakes and bandwidth consumption.

Subscribe Tag Identifier Type

• Topic: Identifies which tag(s) each message is for based on the message topic. The subscribe topic must match what is defined in the “Device Tag” tab.

• Payload: Identifies tags using an identifier within the payload.

Subscribe Clamp Method

Sets how provided values will be clamped to the tag’s data type.

• Reject: values outside of the data type range will be rejected.

• Clamp: values outside of the data type range will be clamped to the data type range.

• Overflow: values outside of the data type range will overflow.

Subscribe Topic Prefix

Sets a prefix string to include in all subscribe topics. Note that this does not automatically add a / level separator to the full topic.

For example, with a prefix of prefix and a tag named New Tag, the default topic will be prefixNew Tag.

Subscribe Topic Suffix

Sets a suffix string to include in all subscribe topics. Note that this does not automatically add a / level separator to the full topic.

For example, with a suffix of suffix and a tag named New Tag, the default topic will be New Tagsuffix.