Description:
Subscribes to a topic and receives messages from an MQTT broker
Tags:
subscribe, MQTT, IOT, consume, listen
Properties:
In the list below, the names of required properties appear in bold. Any other properties (not in bold) are considered optional. The table also indicates any default values, and whether a property is considered “sensitive”.
| Name | Default Value | Allowable Values | Description |
| Broker URI | The URI to use to connect to the MQTT broker (e.g. tcp://localhost:1883). The 'tcp' and 'ssl' schemes are supported. In order to use 'ssl', the SSL Context Service property must be set. | ||
| Client ID | MQTT client ID to use | ||
| User Name | Username to use when connecting to the broker | ||
| Password | Password to use when connecting to the broker | ||
| SSL Context Service | Controller Service API: </br> SSLContextService </br> Implementation: </br> StandardSSLContextService </br> | The SSL Context Service used to provide client certificate information for TLS/SSL connections. | |
| Last Will Topic | The topic to send the client's Last Will to. If the Last Will topic and message are not set then a Last Will will not be sent. | ||
| Last Will Message | The message to send as the client's Last Will. If the Last Will topic and message are not set then a Last Will will not be sent. | ||
| Last Will Retain |
* true * false |
Whether to retain the client's Last Will. If the Last Will topic and message are not set then a Last Will will not be sent. | |
| Last Will QoS Level |
* 0 -  * 1 - * 2 - |
QoS level to be used when publishing the Last Will Message | |
| Session state | true |
* Clean Session * Resume Session |
Whether to start afresh or resume previous flows. See the allowable value descriptions for more details. |
| MQTT Specification Version | 0 |
* AUTO * v3.1.1 * v3.1.0 |
The MQTT specification version when connecting with the broker. See the allowable value descriptions for more details. |
| Connection Timeout (seconds) | 30 | Maximum time interval the client will wait for the network connection to the MQTT server to be established. The default timeout is 30 seconds. A value of 0 disables timeout processing meaning the client will wait until the network connection is made successfully or fails. | |
| Keep Alive Interval (seconds) | 60 | Defines the maximum time interval between messages sent or received. It enables the client to detect if the server is no longer available, without having to wait for the TCP/IP timeout. The client will ensure that at least one message travels across the network within each keep alive period. In the absence of a data-related message during the time period, the client sends a very small "ping" message, which the server will acknowledge. A value of 0 disables keep alive processing in the client. | |
| Topic Filter | The MQTT topic filter to designate the topics to subscribe to. | ||
| Quality of Service(QoS) | 0 |
0 - 1 - 2 - |
The Quality of Service(QoS) to receive the message with. Accepts values '0', '1' or '2'; '0' for 'at most once', '1' for 'at least once', '2' for 'exactly once'. |
| Max Queue Size | The MQTT messages are always being sent to subscribers on a topic. If the 'Run Schedule' is significantly behind the rate at which the messages are arriving to this processor then a back up can occur. This property specifies the maximum number of messages this processor will hold in memory at one time. |
Relationships:
| Name | Description |
| Message | The MQTT message output |
Reads Attributes:
None specified.
Writes Attributes:
| Name | Description |
| mqtt.broker | MQTT broker that was the message source |
| mqtt.topic | MQTT topic on which message was received |
| nmqtt.qos | The quality of service for this message. |
| mqtt.isDuplicate | Whether or not this message might be a duplicate of one which has already been received. |
| mqtt.isRetained | Whether or not this message was from a current publisher, or was "retained" by the server as the last message published on the topic. |
State management:
This component does not store state.