Error 603 when trying to connect to Firebase

Question

I want to send a POST request from a SIM800L module to firebase. So far I have only got the error 603, which tells me that I have no access right?

When I send the same request from Postman installed on my laptop it works fine, read and write access is set to true.

Do I have to send some kind of authentification token with the request or something?

Thanks in advance

---

This is the code for the arduino controlling the SIM800L module

#define SIM800L_RX     27
#define SIM800L_TX     26
#define SIM800L_PWRKEY 4
#define SIM800L_RST    5
#define SIM800L_POWER  23

String apn = "internet.eplus.de";      //APN
String apn_u = "eplus";                //APN-Username
String apn_p = "gprs";                 //APN-Password
String url = "https://benchmark-7913c-default-rtdb.europe-west1.firebasedatabase.app/.json";  //URL of Server

void setup()
{
  pinMode(SIM800L_POWER, OUTPUT);
  digitalWrite(SIM800L_POWER, HIGH);

  Serial.begin(115200);
  Serial.println("ESP32+SIM800L AT CMD Test");
  Serial2.begin(9600, SERIAL_8N1, SIM800L_TX, SIM800L_RX);
  delay(15000);
  while (Serial2.available()) {
    Serial.write(Serial2.read());
  }
  delay(2000);
  gsm_config_gprs();

  gsm_http_post("{\"test\" : \"true\"}");
  Serial.println("Done");
}


void loop() {
  
}

void gsm_http_post( String postdata) {
  Serial.println(" --- Start GPRS & HTTP --- ");
  gsm_send_serial("AT+SAPBR=1,1");
  gsm_send_serial("AT+SAPBR=2,1");
  gsm_send_serial("AT+HTTPINIT");
  gsm_send_serial("AT+HTTPPARA=CID,1");
  gsm_send_serial("AT+HTTPPARA=\"URL\"," + url);
  gsm_send_serial("AT+HTTPPARA=CONTENT,application/x-www-form-urlencoded");
  gsm_send_serial("AT+HTTPDATA=192,5000");
  gsm_send_serial(postdata);
  gsm_send_serial("AT+HTTPACTION=1");
  gsm_send_serial("AT+HTTPREAD");
  gsm_send_serial("AT+HTTPTERM");
  gsm_send_serial("AT+SAPBR=0,1");
}

void gsm_config_gprs() {
  Serial.println(" --- CONFIG GPRS --- ");
  gsm_send_serial("AT+SAPBR=3,1,Contype,GPRS");
  gsm_send_serial("AT+SAPBR=3,1,APN," + apn);
  if (apn_u != "") {
    gsm_send_serial("AT+SAPBR=3,1,USER," + apn_u);
  }
  if (apn_p != "") {
    gsm_send_serial("AT+SAPBR=3,1,PWD," + apn_p);
  }
}

void gsm_send_serial(String command) {
  Serial.println("Send ->: " + command);
  Serial2.println(command);
  long wtimer = millis();
  while (wtimer + 3000 > millis()) {
    while (Serial2.available()) {
      Serial.write(Serial2.read());
    }
  }
  Serial.println();
}

Answer 1

It seems you are adding .json onto the end of the URL before assigning a database location. The error 603 simply means that the location you are trying to access simply does not exist.

Example URL: https://docs-examples.firebaseio.com/rest/saving-data/fireblog/posts.json

Documentation: https://firebase.google.com/docs/database/rest/retrieve-data