Abstract
Provides a standard client to communicate with the mqtt broker
Contents
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 |