pahoMqttExt

Overview

The PahoMqtt Extension implements MQTT client subscription and publication to topics on an MQTT broker where messages on those topics contain current point values. It uses the Eclipse Paho MQTT java client for all MQTT Broker communication. This extension depends on pahoMqtt which is just a wrapper for the runtime Java jar files it requires.

Discovery and learn are not supported functions. As a result, brokers are not discoverable from within the Connectors app and from within the Builder app, the Connectors panel will not show the PahoMqtt Connector.

All PahoMqtt proxy points must be manually bound.

NOTE: Version 1.0.15 and above are built for SkySpark v3.1

Main Configuration

The minimum configuration required to set up an PahoMqtt connector is:

• pahoMqttConn
• pahoMqttBroker
• pahoMqttCleanSession
• pahoMqttQos

Broker Authentication

If username is entered, then a password is also expected. These will be supplied to the broker on connection. If you have a non-authenticating broker, just leave username and password blank.

• username
• password

Password is stored in password db for connector's record id

The connector also supports Client Cert based authentication as used by AWS IOT Core when establishing the SSL/TLS connection. To use this feature, leave the username blank and instead use the pahoClientCertFile and pahoClientKeyFile tags on the connector folio record. These should be the names of the cert and private key pem files as provided by the cert creation tool in AWS IOT Core. e.g. 8588187bbe-certificate.pem.crt and 8588187bbe-private.pem.key

• pahoClientCertFile
• pahoClientKeyFile

The use of client certs only applies when connecting over SSL (i.e. when the pahoMqttBroker starts with ssl:// )

The MQTT SSL port number normally used is 8883, but AWS also supports the ALPN feature such that you can connect to port 443 (HTTPS) but still use the MQTTS protocol. This connector supports the use of this feature.

Payload Structure

As message payload is largely undefined, this connector allows the user to decide how the payload should be parsed to extract point values and how to construct a payload for setting a point value.

You can configure at the connector level what the default payload parser and constructor should be for any points managed by this connector. Even if configured at this level it's possible to override it at the point level.

• pahoMqttParser
• pahoMqttConstructor

Points and Topics

The connector allows for more than one point being subscribed to the same topic for its curVal. If the messages received from the topic only contain a single value, then all subscribed points will be updated to the same curVal. But if the message payloads contain multiple values, you need to also configure the pahoMqttPointName tag on each point. The value for the pahoMqttPointName tag will be used to extract from the Dict returned from the configured message payload parser.

Current Points

PahoMqtt proxy points are configured with pahoMqttCur tag, which maps to a topic at the MQTT Broker:

• pahoMqttConnRef: @conn
• pahoMqttCur: /point/current/topic
• pahoMqttParser: <optional>
• pahoMqttPointName: <optional>

Writable Points

PahoMqtt proxy points are configured to write to remote system points via the pahoMqttWrite tag, which maps to a topic at the MQTT Broker:

• pahoMqttConnRef: @conn
• pahoMqttWrite: /point/write/topic
• pahoMqttConstructor: <optional>
• pahoMqttPointName: <optional>

History

History synchronization is not supported by PahoMqtt. You will need to use collection to store history.