MQTT+PubSubClient+subscribe

#include <ESP8266WiFi.h>

#include <PubSubClient.h>

#define wifi_ssid "My_SSID"

#define wifi_password "My_PW"

#define mqtt_server "m20.cloudmqtt.com"

#define mqtt_user "user" 

#define mqtt_password "password" //

#define humidity_topic "tr_test"

#define cloudmqttport 17208

WiFiClient espClient;

PubSubClient client(mqtt_server, cloudmqttport,callback,espClient);

void setup() {

  Serial.begin(115200);

  setup_wifi();

 // client.setServer(mqtt_server, 17208); // dieser Port ist wichtig

  //client.setCallback(callback);

  //client.subscribe(humidity_topic);

  }

void setup_wifi() {

  delay(10);

  // We start by connecting to a WiFi network

  Serial.println();

  Serial.print("Connecting to ");

  Serial.println(wifi_ssid);

  WiFi.begin(wifi_ssid, wifi_password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(500);

    Serial.print(".");

  }

  Serial.println("");

  Serial.println("WiFi connected");

  Serial.println("IP address: ");

  Serial.println(WiFi.localIP());

}

void reconnect() {

  // Loop until we're reconnected

  while (!client.connected()) {

    Serial.print("Attempting MQTT connection...");

    // Attempt to connect

    if (client.connect("ESP8266Client", mqtt_user, mqtt_password)) {

      Serial.println("connected");

    } else {

      Serial.print("failed, rc=");

      Serial.print(client.state());

      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying

      delay(5000);

    }

  }

}

long lastMsg = 0;

float temp = 0.0;

float hum = 0.0;

float diff = 1.0;

void loop() {

  if (!client.connected()) {

    reconnect();

  }

  client.loop();

  long now = millis();

  if (now - lastMsg > 5000) {

    lastMsg = now;

    float newHum = random(0,100);

    if (newHum != hum) {

      hum = newHum;

       //Serial.print("New humidity:");

       //Serial.println(String(hum).c_str());

      client.publish(humidity_topic, String(hum).c_str(), true);

    }

  }

}

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();

}