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- Communication protocol "MQTT Client Protocol".
- Station address: station address is a particular topic (Topic) or a # character representing # representing all topics. If there is a station with address # on the line, all messages are directed to its I/O tags. Otherwise, the searched KOM looks for a station with the address corresponding to the Topic field in the PUBLISH message is received from the MQTT server.
Note: in the station address, there are not yet supported characters of mask "+" in sense of Topic Filter parameter station address doesn't support wildcard characters "+" corresponding to mask of Topic Filter parameter (yet). - Polling parameters on the Time parameters tab - recommended value is Delay=0.
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| Type of I/O tag | Address | Description | ||||||
|---|---|---|---|---|---|---|---|---|
| I/O tags for reading data sent by MQTT server through PUBLISH message. Note: values of I/O tags are set by D2000 KOM process in the order IN_TOPIC, IN_DATA and IN_ID. It is not necessary for configuration to contain all three I/O tags. | ||||||||
| TxtI |
| Topic (Topic) of received PUBLISH message. | ||||||
| TxtI |
| Data (Payload) of received PUBLISH message. | ||||||
| Ci |
| Identifier of packet (Packet Identifier) of PUBLISH message that depends on the level of validation (QoS). For messages sent with QoS_0, the identifier is zero, for QoS_1 and QoS_2, it is a positive 16-bit number. Note: if MQTT server sends also messages with the QoS_0 level of validation and the ACK_ID I/O tag is configured, then we recommend to activate activate the option New value when changing time option in the Filter tab, so that repeated writing of the value 0 will cause a generation of new value that differs only with time stamp to be generated with a different time stamp. | ||||||
| I/O tag to confirm a receiving of received data of to MQTT server. | ||||||||
| Co |
| If an output I/O tag with ACK_ID address is defined, the D2000 KOM expects confirmation of the processing of each message by writing a copy of value of the IN_ID tag. Not until Only after then it sets values from the next received PUBLISH message (if it was received in the meantime) into the IN_TOPIC, IN_DATA and IN_ID tags (in this order) to the IN_TOPIC, IN_DATA, and IN_ID (if it has been received in the meantime). In case of the QoS_0 level of validationconfirmation, it is therefore necessary to re-enter repeatedly set the value of 0 into the I/O tag ACK_ID to 0. If the I/O tag ACK_ID does not exist, the values are written into the IN_TOPIC, IN_DATA and IN_IDare set I/O tags immediately after the PUBLISH message is publishedreceived and processed. Note: for the messages received with the QoS_0 level of validation, no confirmation of is sent to MQTT server is sent, only the values of the next received PUBLISH message received will be published. | ||||||
| I/O tags for sending values to the MQTT server through PUBLISH message. Note: in order for the D2000 KOM process to send the PUBLISH message messages to the MQTT server, both I/O tags must be defined within one station. | ||||||||
| TxtO |
| Topic within of the PUBLISH message being sent. | ||||||
| TxtO |
| Data (Payload) within of the PUBLISH message being sent. Note: sending the message is carried performed out as a response result of writing to the entry into the OUT_DATA point I/O tag (i.e. if the Topic does not change then it is sufficient to set the OUT_TOPIC point once - e.g. by using default value). | ||||||
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