added check gprs connection at the top of loop and added new 'ensureGPRS' function to ensure GPRS is connected

src/main.cpp

@@ -13,7 +13,6 @@
 #include <Adafruit_GFX.h>
 #include <Adafruit_SSD1306.h>
 
-
 // ================== SIM800L =================
 #define MODEM_RX 16 // ESP32 GPIO16 ← SIM800L TX
 #define MODEM_TX 17 // ESP32 GPIO17 → SIM800L RX (via resistor)
@@ -80,10 +79,6 @@ void oledMQStatus(const String &msg1, const String &msg2, const String &msg3, co
   display.display();
 }
 
-
-
-
-
 // ================= HELPER ======================
 float readAverage(MQUnifiedsensor &sensor, int samples = 5)
 {
@@ -138,7 +133,6 @@ void setup()
     oledGSMStatus("GAGAL JARINGAN");
     oledGSMStatus("RESTART ESP32...");
     ESP.restart(); // Restart ESP32
-    
   }
 
   Serial.println("[GSM] Network OK");
@@ -206,9 +200,52 @@ void setup()
   oledMQStatus("KALIBRASI OK", "...", "Mulai Monitoring", "...");
 }
 
+bool ensureGPRS()
+{
+  if (!modem.isNetworkConnected())
+  {
+    Serial.println("[GSM] Network lost, waiting...");
+    oledGSMStatus("NET PUTUS");
+
+    if (!modem.waitForNetwork(60000L))
+    {
+      Serial.println("[GSM] Network still down!");
+      return false;
+    }
+  }
+
+  if (!modem.isGprsConnected())
+  {
+    Serial.println("[GSM] GPRS lost, reconnecting...");
+    oledGSMStatus("GPRS ULANG");
+
+    modem.gprsDisconnect();
+    delay(1000);
+
+    if (!modem.gprsConnect(apn, user, pass))
+    {
+      Serial.println("[GSM] GPRS reconnect failed!");
+      return false;
+    }
+
+    Serial.println("[GSM] GPRS reconnected");
+  }
+
+  return true;
+}
+
 // =====================================================
 void loop()
 {
+  if (!ensureGPRS())
+  {
+    Serial.println("[GSM] Recover failed, restarting modem...");
+    oledGSMStatus("RESTART MODEM");
+
+    modem.restart();
+    delay(5000);
+    return; // skip this loop
+  }
 
   // =============== MQ135 =================
   MQ135.setA(110.47);
@@ -282,6 +319,9 @@ void loop()
 
   delay(5000);
 
+  client.stop();
+  delay(1000);
+
   if (client.connect(server, port))
   {
     String url = "/api/update?";