Abstract

Manages connections of the yaha Mqtt broker and provides functionality to receive/send messages from/to the managed connections in three service levels ( qos 0 , 1 , 2 )

Contents

- Meta
- Class Connections
- Parameters
- Methods
- acknowledgeMessage
- checkToken
- cleanup
- connect
- disconnect
- getAllMessagesToSend
- isDuplicateQos2message
- onPubrel
- persist
- publishMessage
- restoreFromFile
- setWill
- subscribe
- unsubscribe

Meta

| | |
| --- | --- |
| File | connections.js |
| Abstract | Manages connections of the yaha Mqtt broker and provides functionality to receive/send messages from/to the managed connections in three service levels ( qos 0 , 1 , 2 ) |
| 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 . |

Class Connections

new Connections(configuration)

Creates a connection object This class is part of an MQTT style broker . It manages connections to the broker .

$3

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| configuration | Object | configuration | |

#### configuration properties

| Name | Type | Attribute | Default | Description |
| ---------- | ------------ | ------------ | ------------ | ----------------- |
| fileName | string | | | filename for persistence | |
| directory | string | | | directory ( file path ) for persistence | |
| replyTimeoutInMilliseconds | nubmber | optional | 10000 | timeout to wait for an answer of a http call | |
| inFlightWindow | number | optional | 1 | amount of qos 1 and qos 2 messages send for the same topic at the same time | |
| pubrelTimeoutInMilliseconds | number | optional | 24\3600\1000 | timout to wait for a corresponding pubrel message , default one day | |
| maxRetryCount | number | optional | 10 | amount of resend of messages before forcing a disconnect | |
| maxQueuSize | number | | | maximal amount of entries in a message queue | |

$3

#### acknowledgeMessage

acknowledgeMessage (queueEntry)

Acknowledges a message ( qos = 1 or 2 only )

##### acknowledgeMessage Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| queueEntry | MessageQueueEntry | entry of message queue acknowledged | |

#### checkToken

checkToken (token) => {string, undefined}

Checks , if a token corresponds to a client . Returns the client

##### checkToken Parameters

| Name | Type |
| ---------- | ------------ |
| token | string | |

##### checkToken throws

| Type | Description |
| ---- | ----------- |
| string | error message |

##### checkToken returns

| Type | Description |
| ---- | ----------- |
| string, undefined | clientId . |

#### cleanup

cleanup () => {Object}

Clean up jobs . Call regularly ( example once a minute ) Automatically disconnects clients not sending data until timeout

##### cleanup returns

| Type | Description |
| ---- | ----------- |
| Object | list of clientId beeing automatically disconnected . An object with reason : string and keepAlive : number is included for each disconnected clientId |

#### connect

connect (clientId, host, port, clean, version, keepAlive) => {Object}

Connects a client ( Stores a connection to a client )

##### connect Parameters

| Name | Type | Attribute | Default | Description |
| ---------- | ------------ | ------------ | ------------ | ----------------- |
| clientId | any | | | id of the client | |
| host | string | | | host name | |
| port | string | | | port name | |
| clean | bool | | | true , if the connection will be cleaned on disconnect | |
| version | string | optional | '1 . 0' | client interface version | |
| keepAlive | number | optional | 3600000 | keep alive time in milliseconds . The broker will disconnect any client not sending messages in the keepAlive interval . Default is one hour | |

##### connect throws

| Type | Description |
| ---- | ----------- |
| Error | |

##### connect returns

| Type | Description |
| ---- | ----------- |
| Object | { mqttcode , present } present = = 1 , if an old session is recovered |

#### disconnect

disconnect (clientId)

Disconnects a client

##### disconnect Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| clientId | string | id of the client | |

##### disconnect throws

| Type | Description |
| ---- | ----------- |
| Error | |

#### getAllMessagesToSend

getAllMessagesToSend () => {integer}

Gets all messages to send for all clients function to be called for each message . The function has the parameter QoS and message

##### getAllMessagesToSend returns

| Type | Description |
| ---- | ----------- |
| integer | amount of messages sent |

#### isDuplicateQos2message

isDuplicateQos2message (clientId, topic, qos, dup, packetid)

Checks and remembers a qos2 message . Returns true , if the message is a duplicate

##### isDuplicateQos2message Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| clientId | string | id of the client | |
| topic | string | topic sent | |
| qos | Object | quality of service received from published headers | |
| dup | boolean | true , if the message is a duplicate | |
| packetid | string | id of the sender package | |

#### onPubrel

onPubrel (token, packetid)

Handles a pubrel message , deleting the entry from the qos2 queue

##### onPubrel Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| token | string | client send token | |
| packetid | number | unique identifier of the corresponding publish packet | |

#### persist

async persist ()

Persists all connections

#### publishMessage

publishMessage (payload, qos, retain)

Adds messages that needs to be published

##### publishMessage Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| payload | Message | message to add to a publish storage | |
| qos | Object | quality of service received from published headers | |
| retain | boolean | true , if the message should be retained for future subscribers | |

#### restoreFromFile

async restoreFromFile ()

Restores all clients from last valid saved file

#### setWill

setWill (clientId, will)

Sets the will message of a client

##### setWill Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| clientId | string | id of the client | |
| will | Object | will message configuration | |

#### will properties

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| qos | number | will message quality of service | |
| retain | boolean | true , if the will message is retained | |
| topic | string | topic of the will message | |
| value | string, number | value of the will message | |

#### subscribe

subscribe (clientId, topics) => {Array.}

Subscribes to topics

##### subscribe Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| clientId | string | id of the client | |
| topics | Object | { QoS , topics } or { topic1 : QoS1 , topic2 : QoS2 , . . . } | |

##### subscribe returns

| Type | Description |
| ---- | ----------- |
| Array. | array of QoS values |

#### unsubscribe

unsubscribe (clientId, topics)

Unsubsribes to topics

##### unsubscribe Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| clientId | string | id of the client | |
| topics | Array. | array of topics strings ( topic with wildchars '+' and '#' ) | |