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MessageClient
MessageClient is the base abstraction of a client connecting to a broker in the Messaging-Engine Module module.
The basic capabilities of the client include the following methods
Name |
Parameters |
Description |
sendMessage |
String topic, String message |
Publishes a message on given topic |
subscribeTopic |
String topic |
Subscribes the given topic. Invoked automatically by MessageSubscribers. |
unsubscribeTopic |
String topic |
Unsubscribes the given topic. Invoked automatically by MessageSubscribers. |
And the following properties
Name |
Type |
Description |
subscribers |
Array of MessageSubscribers |
A list of all related subscribers. |
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MQTTClient
MQTTClient is a specialization of the MessageClient included in the Messaging-Engine Module module.
The MQTTClient connects to a MQTT broker and handles the publication as well as subscription of messages.
MQTTClient extends MessageClient and provides the following additional properties.
Name | Type | Description |
protocol | String | Protocol used for the MQTT connections. Default: tcp:// |
url | String | The URL for the MQTT connection |
port | Integer | The port to connect to |
qos | Integer | Quality of Service Range: 0~2 |
isEnabled | Boolean | A boolean value that indicates whether this MQTTClient is enabled (should connect to the broker) |
isConnected | Boolean | A boolean value that indicates whether this MQTTClient is connected to the broker |
KafkaClient
KafkaClient is a specialization of the MessageClient included in the Messaging-Engine Module module.
The KafkaClient connects to a Kafka broker and handles the publication as well as subscription of messages.
KafkaClient extends MessageClient and provides the following additional properties.
Name | Type | Description |
servers | Array of String | List of kafka brokers to connect to. Format: IP:PORT . E.g.: ‘localhost:9092’ |
Note: The consumer used in the implementation expects String-based message contents.
MessageSubscriber
MessageSubscriber is a generic abstraction of a subscriber included in the Messaging-Engine Module module.
It can attach to any kind of MessageClient and will subscribe on that client with the specified topic.
If the client receives a message on given topic, a callback will be made to the subscriber and the message will be evaluated in a scripting context that is specified in the subscribers callback
attribute.
The following properties can be configured for the subscriber:
Name | Type | Description |
clients | Array of MessageClient | A list of all related clients that will be subscribed on. |
topic | String | The topic that will be subscribed |
callback | String | Specifies a script that is evaluated upon the reception of a relevant message. |
Note: Instead of using a specific topic, it is also possible to use *
as a wildcard subscription.
The default scripting context is StructrScript and the message’s content is injected as well and available via retrieve() under the following attributes.
Key | Description |
topic | The topic the message was sent in. |
message | The message’s content. |
MessageClient
MessageClient is the base abstraction of a client connecting to a broker in the Messaging-Engine Module module.
The basic capabilities of the client include the following methods
Name | Parameters | Description |
sendMessage | String topic, String message | Publishes a message on given topic |
subscribeTopic | String topic | Subscribes the given topic. Invoked automatically by MessageSubscribers. |
unsubscribeTopic | String topic | Unsubscribes the given topic. Invoked automatically by MessageSubscribers. |
And the following properties
Name | Type | Description |
subscribers | Array of MessageSubscribers | A list of all related subscribers. |