Device won't transmit to Losant, mqttClient.state -2


I have am working on setting up a temperature and humidity sensor based on the tutorial by
@anaptfox. When testing though, the device says authentication succeeded in the application log, however it doesn’t transmit any data afterward.


I am also getting this readout in the serial monitor:

WiFi connected
IP address:

Authenticating Device...This device is authorized!

Connecting to Losant...-2

I have tried removing everything marked “secure” in the code based on this forum thread but still receive the same error. My hardware and the code I am using are listed below. Does anyone have some ideas how I might fix this?

WEMOS D1 Mini Pro
DHT22 Sensor


#include "DHT.h"
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <Losant.h>

#define DHTPIN 4     // what digital pin the DHT22 is conected to
#define DHTTYPE DHT22   // There are multiple kinds of DHT sensors


// WiFi credentials.
const char* WIFI_SSID = "my_wifi_ssid";
const char* WIFI_PASS = "my_password";

// Losant credentials.
const char* LOSANT_DEVICE_ID = "xxxxxx";
const char* LOSANT_ACCESS_KEY = "xxxxxx";
const char* LOSANT_ACCESS_SECRET = "xxxxxx";

WiFiClientSecure wifiClient;

LosantDevice device(LOSANT_DEVICE_ID);

void connect() {

  // Connect to Wifi.
  Serial.print("Connecting to ");

  // WiFi fix:

  unsigned long wifiConnectStart = millis();

  while (WiFi.status() != WL_CONNECTED) {
    // Check to see if
    if (WiFi.status() == WL_CONNECT_FAILED) {
      Serial.println("Failed to connect to WIFI. Please verify credentials: ");
      Serial.print("SSID: ");
      Serial.print("Password: ");

    // Only try for 30 seconds seconds.
    if(millis() - wifiConnectStart > 30000) {
      Serial.println("Failed to connect to WiFi");
      Serial.println("Please attempt to send updated configuration parameters.");

  Serial.println("WiFi connected");
  Serial.println("IP address: ");

  Serial.print("Authenticating Device...");
  HTTPClient http;
  http.addHeader("Content-Type", "application/json");
  http.addHeader("Accept", "application/json");

  /* Create JSON payload to sent to Losant
   *   {
   *     "deviceId": "575ecf887ae143cd83dc4aa2",
   *     "key": "this_would_be_the_key",
   *     "secret": "this_would_be_the_secret"
   *   }

  StaticJsonBuffer<200> jsonBuffer;
  JsonObject& root = jsonBuffer.createObject();
  root["deviceId"] = LOSANT_DEVICE_ID;
  root["key"] = LOSANT_ACCESS_KEY;
  root["secret"] = LOSANT_ACCESS_SECRET;
  String buffer;

  int httpCode = http.POST(buffer);

  if(httpCode > 0) {
      if(httpCode == HTTP_CODE_OK) {
          Serial.println("This device is authorized!");
      } else {
        Serial.println("Failed to authorize device to Losant.");
        if(httpCode == 400) {
          Serial.println("Validation error: The device ID, access key, or access secret is not in the proper format.");
        } else if(httpCode == 401) {
          Serial.println("Invalid credentials to Losant: Please double-check the device ID, access key, and access secret.");
        } else {
           Serial.println("Unknown response from API");
    } else {
        Serial.println("Failed to connect to Losant API.");



  // Connect to Losant.
  Serial.print("Connecting to Losant...");

  device.connectSecure(wifiClient, LOSANT_ACCESS_KEY, LOSANT_ACCESS_SECRET);

  while(!device.connected()) {
    Serial.println(device.mqttClient.state()); // HERE

  Serial.println("This device is now ready for use!");

void setup() {

  // Wait for serial to initialize.
  while(!Serial) { }

  Serial.println("Device Started");
  Serial.println("Running DHT!");


void report(double humidity, double tempC, double tempF, double heatIndexC, double heatIndexF) {
  StaticJsonBuffer<500> jsonBuffer;
  JsonObject& root = jsonBuffer.createObject();
  root["humidity"] = humidity;
  root["tempC"] = tempC;
  root["tempF"] = tempF;
  root["heatIndexC"] = heatIndexC;
  root["heatIndexF"] = heatIndexF;

int timeSinceLastRead = 0;
void loop() {
   bool toReconnect = false;

  if (WiFi.status() != WL_CONNECTED) {
    Serial.println("Disconnected from WiFi");
    toReconnect = true;

  if (!device.connected()) {
    Serial.println("Disconnected from MQTT");
    toReconnect = true;

  if (toReconnect) {


  // Report every 15 minutes.
  if(timeSinceLastRead > 900000) {
    // Reading temperature or humidity takes about 250 milliseconds!
    // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
    float h = dht.readHumidity();
    // Read temperature as Celsius (the default)
    float t = dht.readTemperature();
    // Read temperature as Fahrenheit (isFahrenheit = true) 
    float f = dht.readTemperature(true) - 4;

    // Check if any reads failed and exit early (to try again).
    if (isnan(h) || isnan(t) || isnan(f)) {
      Serial.println("Failed to read from DHT sensor!");
      timeSinceLastRead = 0;

    // Compute heat index in Fahrenheit (the default)
    float hif = dht.computeHeatIndex(f, h);
    // Compute heat index in Celsius (isFahreheit = false)
    float hic = dht.computeHeatIndex(t, h, false);

    Serial.print("Humidity: ");
    Serial.print(" %\t");
    Serial.print("Temperature: ");
    Serial.print(" *C ");
    Serial.print(" *F\t");
    Serial.print("Heat index: ");
    Serial.print(" *C ");
    Serial.println(" *F");
    report(h, t, f, hic, hif);

    timeSinceLastRead = 0;
  timeSinceLastRead += 100;

Hi @Elizabeth_McGee,

Welcome to the Losant Forums :smile: I am curious, have you stumbled upon or tried the resolution steps from this forum post? And if so, are you still encountering the -2 error?

Thanks so much!

Thank you @ JuliaKempf! I am looking through the forum post and it looks like adding the Losant certificate might solve the problem. I’m attempting to add it using the Wifi101 Firmware Updater but am receiving the following error:

error: declaration of C function 'sint8 spi_flash_read(uint8*, uint32, uint32)' conflicts with sint8 spi_flash_read(uint8 *pu8Buf, uint32 u32Addr, uint32 u32Sz);

I’m guessing this is because my device is flashed using NodeMCU? Do you know of a way to add the certificate with this firmware? I’ve been searching online for a how-to without much luck.

Thank you!

Hi @Elizabeth_McGee,

I just wanted to let you know that we did just recently update the Losant library to support ArduinoJson 6. I would recommend reconfiguring for this change. You can find an updated example here; please let me know if I can answer any further questions!

Thanks so much,

Hi @JuliaKempf,

I have updated the Losant library and installed ArduinoJson 6, but now am receiving errors that the sketch needs to be converted from Json 5 to 6. I am using the same code found in the tutorial by @anaptfox, but don’t have the coding knowledge to make this conversion. Is there a simpler way to install the Losant certificates to get rid of the -2 error? If the Losant library update is what’s needed to resolve the problem, is there a way to get an updated version of the tutorial code?

Thank you,

Hi @Elizabeth_McGee,

It can be sometimes difficult to debug these problems due to the range of device components and possible failures. This can be even more difficult if trying to accomplish multiple tasks within one step. To begin debugging, we recommend breaking this task into parts to deduce where the issue is transpiring!

The tutorial code you are following does two things, it reads from your sensor and reports to Losant. Your first step to debugging is to ensure you are able to successfully connect to Losant. The two code pieces have been combined in the second snippet. The first snippet is the code that reads the sensor. Removing the sensor code will allow you to exclusively connect to Losant without attempting to read values from the DHT. This example also includes the code to connect to Losant (but utilizes a different sensor), this can be a helpful reference to see how the Losant code functions.

Please let me know your findings after attempting to connect, I’ll be interested to see if the error continues or changes. :smile: In addition, you can also find a detailed changelog for this upgrade here.


Thank you for the information @JuliaKempf! I managed to get the rest of the code converted for the JSON upgrade based on the link you provided. I also isolated the Losant connection code from the DHT code but still seem to be having the same problem. The -2 isn’t appearing in the serial monitor anymore but I think this is because the new MQTT library that I had to install while making the JSON upgrade doesn’t include the error codes.

During the initial sketch upload from IDE, the application log in Losant shows “Authentication succeeded” but nothing happens after this and the IDE serial monitor shows a bunch of dots. If I change the code to an usecure connection, it will also register in Losant as unsecure but still nothing happens after this.

I initially built the device in July, 2018 and it worked without any problems, then sometime last year it was no longer able to connect.

Is there a way to add the Losant certificate in the sketch itself or something else I should try?

Thank you for your help!