User Manual

bool unsubscribe (void)

Unsubscribes to the topic if you previously called .subscribe.

Parameters: None

Returns: 'True' (1) if the operation succeeded, otherwise 'false' (0).

bool subscribed (void)

Indicates whether you are currently susbcripted to this topic or not.

Parameters: None

Returns: 'True' (1) if you are subscribed, otherwise 'false' (0).

Publishing Data via 'Print'

One important thing to keep in mind with AdafruitMQTTTopic is that every .print* function corresponds to an MQTT

publication request.

The following code will result in three different MQTT publications:

/**************************************************************************/

/*!

@brief MQTT subscribe event callback handler

@param topic The topic causing this callback to fire

@param message The new value associated with 'topic'

@note 'topic' and 'message' are UTF8Strings (byte array), which means

they are not null-terminated like C-style strings. You can

access its data and len using .data & .len, although there is

also a Serial.print override to handle UTF8String data types.

/**************************************************************************/

void subscribed_callback(UTF8String topic, UTF8String message)

{

// Print out topic name and message

Serial.printf("["); Serial.print(topic); Serial.printf("]");

Serial.print(" : message = ") ;

Serial.println(message);

// Unsubscribe if message = "stop"

if ( message == "stop" )

{

Serial.print("Unsubscribing ... ");

mqttTopic.unsubscribe(); // Will halt if fails

Serial.println("OK");

}