Abstract

Provides a standard client to communicate with the mqtt broker

Contents

• Meta
• Type definitions
• Class MqttClient
  • Parameters
  • Members
  • Methods
    • _createMemoryUsageMessage
    • close
    • isShuttingDown
    • on
    • publish
    • reconnect
    • registerCloseFunction
    • registerRecipient
    • registerSender
    • run
    • updateSubscriptions

Meta

| | | | --- | --- | | File | mqttclient.js | | Abstract | Provides a standard client to communicate with the mqtt broker | | Author | Volker Böhm | | Copyright | Copyright ( c ) 2020 Volker Böhm | | License | This software is licensed under the GNU LESSER GENERAL PUBLIC LICENSE Version 3 . It is furnished "as is" , without any support , and with no warranty , express or implied , as to its usefulness for any purpose . |

Type definitions

LogPattern {Object}

| Name | Type | Description | | ---- | ---- | ------- | | topic | string | log topic pattern | | | module | string | module to log , "send" , "receive" or "all" ( for all modules ) | | | level | number | log level for the pattern | |

Callback definitions

PollCallback

Callback to retrieve messages to be sent to the mqtt broker

PollCallback returns

| Type | Description | | ---- | ----------- | | Array.<Message>, Message | messages to send to the broker |

Class MqttClient

new MqttClient(options)

Creates a standard mqtt client , connects and subscribes to the broker

MqttClient Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | options | Object | options to provide for connection | |

options properties

| Name | Type | Attribute | Default | Description | | ---------- | ------------ | ------------ | ------------ | ----------------- | | clientId | string | | | unique id of the client | | | broker | Object | | | information of the broker to connect to | | | listener | number | | | port this client will listen to | | | version | string | optional | '1 . 0' | interface version | | | keepAliveInSeconds | string | optional | | connection keep alive time in seconds | | | clean | boolean | optional | true | clean the broker session on disconnect | | | retry | number | | | amount of retries to send messages to the broker | | | log | Array.<LogPattern> | | | logging settings | |

broker properties

| Name | Type | Description | | ---------- | ------------ | ----------------- | | host | string | hostname of the broker | | | port | number | port of the broker | |

MqttClient Members

| Name | Type | description | | ------------ | ------------ | ------------ | | connected | boolean | Connection status . true , iff connected | | token | Object.<send:string, receive:string> | Send and receive token to be used to communicate with the mqtt broker | | version | string | Gets/Sets the interface version to use |

MqttClient Methods

_createMemoryUsageMessage

_createMemoryUsageMessage () => {Message}

Creates a message showing the memory usage

_createMemoryUsageMessage returns

| Type | Description | | ---- | ----------- | | Message | the memory usage message with the topic $SYS/ [ clientId ] /memory usage |

close

async close ()

closes the client by shutting down all services and loops

isShuttingDown

isShuttingDown () => {boolean}

checks , if the client is shutting down . Every loop must stop once isShuttingDown is true

isShuttingDown returns

| Type | Description | | ---- | ----------- | | boolean | true , iff shutting down |

on

on (event, callback)

Sets a callback .

on Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | event | string | supports 'shutdown' | | | callback | function | | |

on throws

| Type | Description | | ---- | ----------- | | Error | if the event is not supported | | Error | if the callback is not 'function' |

publish

publish (message, serviceName)

Publishes a message to the broker

publish Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | message | Message | message to publish | | | serviceName | string | name of the publishing service | |

message properties

| Name | Type | Description | | ---------- | ------------ | ----------------- | | qos | number | quality of service ( 0 , 1 , 2 ) | | | retain | boolean | true to create a retain message | |

reconnect

async reconnect ()

Connects and subscribes to the broker

registerCloseFunction

registerCloseFunction (closeFunction)

Registers close functions . It will be called when the client close function is called

registerCloseFunction Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | closeFunction | function | function to be called on close commands | |

registerRecipient

async registerRecipient (serviceName, subscriptions, callback)

Registeres a recipient

registerRecipient Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | serviceName | string | name of the subscribing service | | | subscriptions | Object | subscription entries of format { topic : qos , topic : qos , . . . } | | | callback | function | function to send received messages to | |

registerRecipient throws

| Type | Description | | ---- | ----------- | | Error | If subscriptions are not well formatted or callback is not a function |

registerSender

registerSender (intervalInMilliseconds, callback)

Registeres a service sending messages in intervals . The service must provide a function ( callback ) without parameters returing an array of messages . The messages will then be sent to the broker

registerSender Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | intervalInMilliseconds | number | interval in milliseconds to call the senders callback | | | callback | PollCallback | function to call | |

run

async run ()

Starts the mqttclient . Opens the listener and connects to the broker

updateSubscriptions

async updateSubscriptions (serviceName, subscriptions)

Updates the subscriptions

updateSubscriptions Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | serviceName | string | name of the subscribing service | | | subscriptions | Object | subscription entries of format { topic : qos , topic : qos , . . . } | |

updateSubscriptions throws

| Type | Description | | ---- | ----------- | | Error | If subscriptions are not well formatted |