LedSubscribe.ino

int led1 = D3;

void setup() 
{
    // Set both LED pins as outputs
    
    pinMode(led1, OUTPUT);
    
    // Set both LED's to off by writing
    // LOW to the pin.
    
    digitalWrite(led1, LOW);
    
    // Register the subscription and assign
    // a handler for it
    
    Particle.subscribe("ledToggle", myHandler);
}

// The handler for the subscription

void myHandler(String event, String data)
{
    if(data == "on")
        digitalWrite(led1, HIGH);
       
    
    if(data == "off")
         digitalWrite(led1, LOW);
}

Particle.Publish().ino

// Send an event by name

Particle.publish(const char *eventName);
Particle.publish(String eventName);

// Send data via a named event

Particle.publish(const char *eventName, const char *data);
Particle.publish(String eventName, String data);

// Return values

boolean (true or false)

// Example usage

bool success;
success = Particle.publish("button-pressed");

if (!success) {
  // triggered if event publish failed
}

Particle.Subscribe().ino

void setup()
{
  Particle.subscribe("button-pressed", handler);
  Serial.begin(9600);
}

void handler(String event, String data)
{
  Serial.print(event);
  Serial.print(", data: ");

if (data)
{
    Serial.print(data);
  else
    Serial.print("NULL");
}

Serial.println();

}

PushButtonPublish.ino

// Register the pin that the button is
// connected to

int buttonPin = D6;

// Register and Initialise a flag to hold 
// current state.

bool pressed = false;

// Register a delay period to slow things
// down if needed.

int period = 100;

// Perform the program setup

void setup() 
{
    // Set the button pin as an input
    
    pinMode(buttonPin, INPUT);
    
    // Set the pressed flag to false
    
    bool pressed = false;
    
    // Set the initial state of subscriber
    // to off just in case.
    
     Particle.publish("ledToggle", "off");
    
}

// Loop through the program

void loop() 
{
    // Check to see if the button is pressed
    // or not. The use of flags ensures that
    // only a singular event is called for 
    // each state.
    
    if(digitalRead(buttonPin) == LOW)
    {
        // The button is released. Check against the flag
        // to see if it has already been set. If so return.
        
        if(pressed == false)
            return;
        
        // The flag has not been set so set it now.
        
        pressed = false;
        
        // Publish the off event.
        
        Particle.publish("ledToggle", "off");
    }
    else if(digitalRead(buttonPin) == HIGH)
    {
        // The button is pressed. Check against the flag
        // to see if it has already been set. If so return.
        
         if(pressed == true)
            return;
        
        // The flag has not been set so set it now.
        
        pressed = true;
        
        // Publish the on event.
        
        Particle.publish("ledToggle", "on");
    }
    
    // Use a delay to slow down the loop; thus allowing
    // time for operations to complete.
    
    delay(period);
}