Fehler beim "Serializing" von Temperaturdaten

#include <Wire.h>

#include <Adafruit_SHT31.h>

#include <ESP8266WiFi.h>

#include <PubSubClient.h>

#include <SPI.h>

// Replace with your WiFi credentials

const char* ssid = "Test123";

const char* password = "Test123";

// Replace with your MQTT broker details

const char* mqtt_server = "Test123";

const int mqtt_port = 1883;

const char* mqtt_topic = "sensor_data";

// Create an instance of the SHT85 sensor

Adafruit_SHT31 sht;

// Create an instance of the WiFi client

WiFiClient espClient;

// Create an instance of the MQTT client

PubSubClient client(espClient);

void setup() {

  // Start the serial communication

  Serial.begin(9600);

  // Connect to Wi-Fi

  WiFi.begin(ssid, password);

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

    delay(1000);

    Serial.println("Connecting to WiFi...");

  }

  Serial.println("Connected to WiFi");

  // Connect to MQTT broker

  client.setServer(mqtt_server, mqtt_port);

  // Initialize the SHT85 sensor

  if (!sht.begin(0x44)) {

    Serial.println("SHT85 not found. Check wiring!");

    while (1);

  }

}

void loop() {

  // Read sensor data

  float temperature = sht.readTemperature();

  float humidity = sht.readHumidity();

  // Print sensor data to Serial Monitor

  Serial.print("Temperature: ");

  Serial.print(temperature);

  Serial.print(" °C, Humidity: ");

  Serial.print(humidity);

  Serial.println(" %");

  // Publish sensor data to MQTT

  if (client.connect("ESP8266Client")) {

    char tempStr[10];

    char humStr[10];

    dtostrf(temperature, 4, 2, tempStr);

    dtostrf(humidity, 4, 2, humStr);

    client.publish(mqtt_topic, tempStr);

    //client.publish(mqtt_topic, humStr);

    client.disconnect();

  }

  // Wait for a while before reading the sensor again

  delay(5000);

}