#define TINY_GSM_MODEM_SIM7600  // SIM7600 AT instruction is compatible with A7670
#define SerialAT Serial1
#define SerialMon Serial
#define TINY_GSM_USE_GPRS true
#include <TinyGsmClient.h>
#include <SocketIOclient.h>
#include <ArduinoHttpClient.h>
#include <DHT.h>
#include <DHT_U.h>
#include <ArduinoJson.h>
#define RXD2 27    //VVM MODULE RXD INTERNALLY CONNECTED
#define TXD2 26    //VVM MODULE TXD INTERNALLY CONNECTED
#define powerPin 4 ////VVM MODULE ESP32 PIN D4 CONNECTED TO POWER PIN OF A7670C CHIPSET, INTERNALLY CONNECTED
#define DHTPIN 5   // Pin which is connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22 (AM2302)
#define USE_SERIAL Serial
DHT dht(DHTPIN, DHTTYPE);
JsonDocument doc;
char jsonOutput[128];
const char* serverUrl = "192.168.1.238";
const int serverPort = 3000;


char a, b;

const char apn[]      = ""; //APN automatically detects for 4G SIM, NO NEED TO ENTER, KEEP IT BLANK




TinyGsm        modem(SerialAT);

TinyGsmClient client(modem);
HttpClient http = HttpClient(client, serverUrl, serverPort);
void setup()
{
  Serial.begin(115200);

  pinMode(powerPin, OUTPUT);
  digitalWrite(powerPin, LOW);
  delay(100);
  digitalWrite(powerPin, HIGH);
  delay(1000);
  digitalWrite(powerPin, LOW);

  Serial.println("nconfiguring VVM Module. Kindly wait");

  delay(10000);

  SerialAT.begin(115200, SERIAL_8N1, RXD2, TXD2);
 
  dht.begin();
  // Restart takes quite some time
  // To skip it, call init() instead of restart()
  DBG("Initializing modem...");
  if (!modem.init()) {
    DBG("Failed to restart modem, delaying 10s and retrying");
    return;
  }
  // Restart takes quite some time
  // To skip it, call init() instead of restart()
  DBG("Initializing modem...");
  if (!modem.restart()) {
    DBG("Failed to restart modem, delaying 10s and retrying");
    return;
  }

  String name = modem.getModemName();
  DBG("Modem Name:", name);

  String modemInfo = modem.getModemInfo();
  DBG("Modem Info:", modemInfo);

  Serial.println("Waiting for network...");
  if (!modem.waitForNetwork()) {
    Serial.println(" fail");
    delay(5000);
    return;
  }
  Serial.println(" success");

  if (modem.isNetworkConnected()) {
    Serial.println("Network connected");
  }

  // GPRS connection parameters are usually set after network registration
  Serial.print(F("Connecting to "));
  Serial.print(apn);
  if (!modem.gprsConnect(apn)) {
    Serial.println(" fail");
    delay(10000);
    return;
  }
  Serial.println(" success");

  if (modem.isGprsConnected()) {
    Serial.println("LTE module connected");
    
  }

 
 

}

void loop()
{
 
  // Read temperature and humidity values
  float h = dht.readHumidity();
  float t = dht.readTemperature();

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

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.println(" *C");
  String postData = "{"temperature":" + String(t) + ","humidity":" + String(h) + "}";
  http.beginRequest();
  http.post("/api/device-data");
  http.sendHeader("Content-Type", "application/json");
  http.sendHeader("Content-Length", postData.length());
 
  http.beginBody();
  http.print(postData);
  

  // read the status code and body of the response
  int statusCode = http.responseStatusCode();
  String response = http.responseBody();

  Serial.print("Status code: ");
  Serial.println(statusCode);
  Serial.print("Response: ");
  Serial.println(response);
http.endRequest();
  delay(2000); // Delay between sensor readings
}

I am trying to send data to my node.js server using GPRS for SIM module A7672S but from WIFI it receives successfully. My node.js code is below

app.post('/api/device-data', async (req, res) => {
  const { temperature, humidity } = req.body;

  if (temperature && humidity) {
    const newData = new DeviceData({ temperature, humidity });
    await newData.save();
    console.log(`Received data: Temperature=${temperature}, Humidity=${humidity}`);
    res.status(200).json({ message: 'Sensor data received successfully' });
  } else {
    res.status(400).send('Invalid data');
  }
});

I don’t know why this is not able to send data using GPRS but with WIFI it runs smoothly.

my response is –>>>
In my response side I got very different error here my response is below

Status code: -3

Response: 

Humidity: 66.40 %   Temperature: 27.90 *C