unsubscribe method
Unsubscribe from a topic.
Some brokers(AWS for instance) need to have each un subscription acknowledged, use
the expectAcknowledge
parameter for this, default is false.
Implementation
void unsubscribe(String topic, {expectAcknowledge = false}) {
final unsubscribeMsg = MqttUnsubscribeMessage()
.withMessageIdentifier(
messageIdentifierDispenser.getNextMessageIdentifier())
.fromTopic(topic);
if (expectAcknowledge) {
unsubscribeMsg.expectAcknowledgement();
}
connectionHandler!.sendMessage(unsubscribeMsg);
pendingUnsubscriptions[unsubscribeMsg.variableHeader!.messageIdentifier] =
topic;
}