a working demo of public/private publish / subscribe for multiple cores

publish_demo.ino

#define publish_delay 10000

#define PUBLISH_TO "some_private_event_1"
#define PUBLIC_EVENT "some_public_event_1"
unsigned int lastPublish = 0;

void setup() {
    Serial.begin(115200);
    
    //the firmware uses the event name to figure out which handler it should toss things to, and doesn't select based on privacy, so we need to also make the event names differ in this example.
    Spark.subscribe("some_public", publicEventHandler);
    Spark.subscribe("some_private", privateEventHandler, MY_DEVICES);
}

void loop() {
    unsigned int now = millis();
    
    if ((now - lastPublish) > publish_delay) {
        Serial.println("Publishing...");
        
        Spark.publish(PUBLIC_EVENT, String(now));
        Spark.publish(PUBLISH_TO, String(now), 60, PRIVATE);
        
        lastPublish = now;
    }
}

void publicEventHandler(const char* name, const char* data) {
    Serial.println("heard event: " + String(name));
}

void privateEventHandler(const char* name, const char* data) {
    Serial.println("heard private event: " + String(name));
}