MATLAB: Mqtt via ESP8266 connected but not subscribing

Question

Hello,

yesterday: i changed the way i collect data from my thinspeak channel from the ThingSpeak arduino library to mqtt. it worked like a charm.

today: my ESP8266 tells me that he is connected. but no data comes from the subscription and so the esp8266 will try to reconnect.

Is there a problem with your Server, or is it an license problem?

I think i reached the maximum of mqtt clients (3 clients in free mode). Is there a way to reset the clients to reconnect?

Best regards

Christian

my test code:

#include <EEPROM.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
const char ssid[] = "xxxxxxx"; //Insert your SSID
const char pass [] = "xxxxxxxxx";  /Insert Your password
const char* mqtt_server = "mqtt.thingspeak.com";
const char* mqttUserName = "xxxxxxxxxxx"; // Thingspeak username.
const char* mqttPass = "xxxxxxxxxxxxxxxx"; // Change to your MQTT API Key from Account > MyProfile.
const char* ChannelID = "xxxxxx"; // Thingspeak Channel ID
const char* APIKey = "xxxxxxxxxxxxxxxx"; // Thingspeak Channel Read API Key
String Temp_String;
WiFiClient espClient;
PubSubClient client(espClient);
const byte ledPin = 0; // Pin with LED on Adafruit Huzzah
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Data received: ");
  Serial.print("Temperature ");
  for (int i = 0; i < length; i++) {
    char receivedChar = (char)payload[i];
    Temp_String += (char)payload[i];
  }
  float TS_Temp = Temp_String.toFloat();
  Serial.print(TS_Temp);
  TS_Temp = 0;
  Temp_String = "";
  Serial.println();
}
void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP8266", mqttUserName, mqttPass)) {
      Serial.println("connected");
      // ... and subscribe to topic
      client.subscribe("channels/INSERT YOUR CHANNEL ID HERE/subscribe/fields/field1/INSERT YOUR API READ KEY HERE");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}
void setup()
{
  Serial.begin(115200);
  delay(250);
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
  WiFi.disconnect();
  delay(100);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(500);
  }
  Serial.print("OK");
  Serial.println();
}
void loop()
{
  if (!client.connected()) {
    reconnect();
  }
  client.loop();
}

Answer 1

The mqtt server should reset the count when your devces disconnect, though there may be a short delay. Are you still having this issue after waiting a bit? Do you still have multiple connections?