MQTTDelayTest.ino

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

const char* ssid = "...";
const char* password = "...";
const char* mqtt_server = "...";

WiFiClient espClient;
PubSubClient client(espClient);

long lastMsg = 0;

void setup() {
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void setup_wifi()
{
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
}

void reconnect()
{
  // Loop until we're reconnected
  while (!client.connected())
  {
    // Attempt to connect
    if (client.connect("c1"))
    {
      client.publish("controllers/c1", "online");
      client.subscribe("controllers/c1/commands");
    }
    else
    {
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void loop()
{
  if (!client.connected())
  {
    reconnect();
  }
  client.loop();

  long now = millis();
  if (now - lastMsg > 10)
  {
    lastMsg = now;
    client.publish("controllers/c1", "1");
  }
}

MQTTDelayTest.pde

import mqtt.*;

MQTTClient client;

int timer = 0;
PFont font;

void setup()
{
    size(400, 400);
    client = new MQTTClient(this);
    client.connect("mqtt://localhost", "mqtt-delay-test");
    client.subscribe("controllers/c1");
    client.subscribe("controllers/c2");
    
    font = createFont("Courier", 20);
    textFont(font);
}

void draw()
{
    background(200);
    noStroke();
}

void messageReceived(String topic, byte[] payload)
{
    String incomingMessage = new String(payload);
    //println("[" + topic + "] " + incomingMessage);
    
    if (topic.equals("controllers/c1"))
    {
        int value = Integer.parseInt(incomingMessage);
        if (value == 1)
        {
            fill(0);
            text(millis() - timer, width / 2 - 100, 100);
            ellipse(width / 2 - 100, height / 2, millis() - timer, millis() - timer);
            timer = millis();
        }
    }
    
    if (topic.equals("controllers/c2"))
    {
        int value = Integer.parseInt(incomingMessage);
        if (value == 1)
        {
            fill(0);
            text(millis() - timer, width / 2 + 100, 100);
            ellipse(width / 2 + 100, height / 2, millis() - timer, millis() - timer);
            timer = millis();
        }
    }    
}