Blynk 2.0 and MQTT

Hi, i am using ESP32 TT CALL SIM 800 and not be able to make it work with mqtt and blynk together.
The MQTT doesn’t connect. If I comment out the Blynk.begin() and The MQTT is connected without any problems.

This is my code:

#define BLYNK_PRINT Serial

/* Fill-in your Template ID (only if using Blynk.Cloud) */
#define BLYNK_DEVICE_NAME "Entra Energy"
#define BLYNK_AUTH_TOKEN "ag1p2OnHsvHusY3-ZsOYAjuOgTsMXyxS";

#define SIM800L_IP5306_VERSION_20190610
// Select your modem:
#define TINY_GSM_MODEM_SIM800 // Modem is SIM800L

// Set serial for debug console (to the Serial Monitor, default speed 115200)
#define SerialMon Serial
// Set serial for AT commands
#define SerialAT Serial1

// Define the serial console for debug prints, if needed
#define TINY_GSM_DEBUG SerialMon

// set GSM PIN, if any
#define GSM_PIN ""
char auth[] = "ag1p2OnHsvHusY3-ZsOYAjuOgTsMXyxS";
// Your GPRS credentials, if any
const char apn[] = ""; // APN (example: use
const char gprsUser[] = "";
const char gprsPass[] = "";

// SIM card PIN (leave empty, if not defined)
const char simPIN[]   = ""; 

// MQTT details
const char* broker = "";                    // Public IP address or domain name
const char* mqttUsername = "";  // MQTT username
const char* mqttPassword = "";  // MQTT password

const char* topicOutput1 = "esp/output1";
const char* topicOutput2 = "esp/output2";
const char* topicTemperature = "esp/temperature";
const char* topicHumidity = "esp/humidity";

// Define the serial console for debug prints, if needed

#include <Wire.h>
#include <TinyGsmClient.h>
#include <BlynkSimpleTinyGSM.h>

  #include <StreamDebugger.h>
  StreamDebugger debugger(SerialAT, SerialMon);
  TinyGsm modem(debugger);
  TinyGsm modem(SerialAT);

#include <PubSubClient.h>

TinyGsmClient client(modem);
PubSubClient mqtt(client);

// TTGO T-Call pins
#define MODEM_RST            5
#define MODEM_PWKEY          4
#define MODEM_POWER_ON       23
#define MODEM_TX             27
#define MODEM_RX             26
#define I2C_SDA              21
#define I2C_SCL              22

#define OUTPUT_1             2
#define OUTPUT_2             15

uint32_t lastReconnectAttempt = 0;

// I2C for SIM800 (to keep it running when powered from battery)
TwoWire I2CPower = TwoWire(0);

TwoWire I2CBME = TwoWire(1);

#define IP5306_ADDR          0x75
#define IP5306_REG_SYS_CTL0  0x00

float temperature = 0;
float humidity = 0;
long lastMsg = 0;

bool setPowerBoostKeepOn(int en){
  if (en) {
    I2CPower.write(0x37); // Set bit1: 1 enable 0 disable boost keep on
  } else {
    I2CPower.write(0x35); // 0x37 is default reg value
  return I2CPower.endTransmission() == 0;

void mqttCallback(char* topic, byte* message, unsigned int len) {
  Serial.print("Message arrived on topic: ");
  Serial.print(". Message: ");
  String messageTemp;
  for (int i = 0; i < len; i++) {
    messageTemp += (char)message[i];

  // Feel free to add more if statements to control more GPIOs with MQTT

  // If a message is received on the topic esp/output1, you check if the message is either "true" or "false". 
  // Changes the output state according to the message
  if (String(topic) == "esp/output1") {
    Serial.print("Changing output to ");
    if(messageTemp == "true"){
      digitalWrite(OUTPUT_1, HIGH);
    else if(messageTemp == "false"){
      digitalWrite(OUTPUT_1, LOW);
  else if (String(topic) == "esp/output2") {
    Serial.print("Changing output to ");
    if(messageTemp == "true"){
      digitalWrite(OUTPUT_2, HIGH);
    else if(messageTemp == "false"){
      digitalWrite(OUTPUT_2, LOW);

boolean mqttConnect() {
  SerialMon.print("Connecting to ");

  // Connect to MQTT Broker without username and password
  boolean status = mqtt.connect("GsmClientN");

  if (status == false) {
    SerialMon.println(" fail");
    return false;
  SerialMon.println(" success");

  return mqtt.connected();

void setup() {
  // Set console baud rate

  // Keep power when running from battery
  bool isOk = setPowerBoostKeepOn(1);
  SerialMon.println(String("IP5306 KeepOn ") + (isOk ? "OK" : "FAIL"));

  // Set modem reset, enable, power pins
  digitalWrite(MODEM_PWKEY, LOW);
  digitalWrite(MODEM_RST, HIGH);
  digitalWrite(MODEM_POWER_ON, HIGH);
  pinMode(OUTPUT_1, OUTPUT);
  pinMode(OUTPUT_2, OUTPUT);

  // Set GSM module baud rate and UART pins
  SerialAT.begin(115200, SERIAL_8N1, MODEM_RX, MODEM_TX);

  // Restart takes quite some time
  // To skip it, call init() instead of restart()
  SerialMon.println("Initializing modem...");
  // modem.init();

  String modemInfo = modem.getModemInfo();
  SerialMon.print("Modem Info: ");

  // Unlock your SIM card with a PIN if needed
  if ( GSM_PIN && modem.getSimStatus() != 3 ) {

  SerialMon.print("Connecting to APN: ");
  if (!modem.gprsConnect(apn, gprsUser, gprsPass)) {
    SerialMon.println(" fail");
  else {
    SerialMon.println(" OK");
  if (modem.isGprsConnected()) {
    SerialMon.println("GPRS connected");

  // MQTT Broker setup
  mqtt.setServer(broker, 1883);
  Blynk.begin(auth, modem, apn, gprsUser, gprsUser);

void loop() {
  if (!mqtt.connected()) {
    SerialMon.println("=== MQTT NOT CONNECTED ===");
    // Reconnect every 10 seconds
    uint32_t t = millis();
    if (t - lastReconnectAttempt > 10000L) {
      lastReconnectAttempt = t;
      if (mqttConnect()) {
        lastReconnectAttempt = 0;

  long now = millis();
  if (now - lastMsg > 30000) {
    lastMsg = now;
    // Temperature in Celsius
    temperature = 10;   
    // Uncomment the next line to set temperature in Fahrenheit 
    // (and comment the previous temperature line)
    //temperature = 1.8 * bme.readTemperature() + 32; // Temperature in Fahrenheit
    // Convert the value to a char array
    char tempString[8];
    dtostrf(temperature, 1, 2, tempString);
    Serial.print("Temperature: ");
    mqtt.publish(topicTemperature, tempString);

    humidity = 20;
    // Convert the value to a char array
    char humString[8];
    dtostrf(humidity, 1, 2, humString);
    Serial.print("Humidity: ");
    mqtt.publish(topicHumidity, humString);


Thank you in advance!

Are you using Node-Red?


Yes. I am trying to send to Node-Red mqtt node and to blynk app at the same time.


I don’t run any Blynk code on my devices, just MQTT code.
I use the Blynk IoT contrib to send/receive data to/from Blynk.


Thank you very much I will check this Blynk IoT contrib.
Is it good idea to send the data via Blynk Api GET from the device or your suggestion is to use Node-Red Blynk IoT contrib?


I installed this Node-Red Blynk IOT contrib, but I cant connect. Can you help me please?
I am attaching a screenshot of the node config

You must give a name. You’'ll have to select that name in connection in the properties window of the write-node and fill in the right virtual stream, pinmode stays on fixed.

Like this:

btw, i use Node-Red to communicate between Siemens LOGO 8 and Blynk.

1 Like

You can do either (or both) but the advantage of the contrib is that it establishes an open connection to the Blynk server and will trigger a Write Event node whenever a widget in the app changes state. This means that if you have a button widget attached to V1 then the Write Event node attached to V1 will go from 0 to 1 when the app button is turned from off to on.
To achieve the same functionality with a GET API you would need to keep polling each virtual pin to look for status changes.

Have you read this topic…


Thank you very much. The problem is that the nodes says disconnected. When i try the same blynk nodes on my localhost Node-Red they are connected properly. When I use Node-Red on Cloud VM blynk nodes can’t connect

Thank you very much very useful topic! My problem now is that the blynk nodes cant connect.

It’s probably resolving the wrong Blynk cloud server.
Read this, and add the full server URL…


I am trying to use the full URL, but still disconected

And does the API call still work from this same machine?


You’re not giving much info… is your datastream setup right? Did you already try “restart flow” in Node-Red?

Yes, I am using http request node and sent value to blynk iot dashboard successfully.
I am using V1 in datastream.

Open a terminal session and stop NR with node-red-stop then start it again with node-red-start.
Do you see any clues about what may be causing the issue?


Then you need to use also V1 in the write node, now you’re using V5?

I am using Node-Red on cloud (digital ocean virtual machine) so I reboot the machine, but nothing.
Also if I run Node-Red locally it connects without problems. Is it possible this issue to be related with Node.js/Node-Red versions?

So you didn’t like this suggestion….


I tried it. But it says not such command when I type node-red-stop in the terminal