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.. _`.fld-FinderOpta.fld-Functions.fld-Read.MQTT_ReadTopicString`:


.. index::
   single: MQTT_ReadTopicString

.. _`MQTT_ReadTopicString`:

``MQTT_ReadTopicString`` (FUN)
------------------------------

FUNCTION MQTT_ReadTopicString : WORD




This function subscribes to the specified MQTT topic and returns published messages as strings.

The output ``valid`` is set to ``TRUE`` when a publication occurs
on the topic and the message payload is copied into ``value``.





InOut:
    +--------+--------------------------+-----------------+------------------------------------------------------------+
    | Scope  | Name                     | Type            | Comment                                                    |
    +========+==========================+=================+============================================================+
    | Return | ``MQTT_ReadTopicString`` | ``WORD``        | Status code returned by the runtime (0 means "no errors"). |
    +--------+--------------------------+-----------------+------------------------------------------------------------+
    | Inout  | ``id``                   | ``WORD``        | Operation identifier used by the runtime.                  |
    +--------+--------------------------+-----------------+------------------------------------------------------------+
    | Input  | ``topic``                | ``STRING(127)`` | MQTT topic name.                                           |
    +        +--------------------------+-----------------+------------------------------------------------------------+
    |        | ``qos``                  | ``WORD``        | Quality of Service level.                                  |
    +--------+--------------------------+-----------------+------------------------------------------------------------+
    | Output | ``value``                | ``STRING(244)`` | String value received from the topic.                      |
    +        +--------------------------+-----------------+------------------------------------------------------------+
    |        | ``valid``                | ``BOOL``        | ``TRUE`` when a valid value has been received.             |
    +--------+--------------------------+-----------------+------------------------------------------------------------+







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