http.getString() return blank

[igorfelluga]

Hi
I have a simple code that read a json and display result on lcd.
After some month I resumed it but I think that some update (Arduino CLI o other) give me a problem with http.getString() that return empty string.
To do a simple test I did an empty project with only wifi connection http request.
Here my code:

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>

const char* ssid = "FUNCOOL";
const char* password = "1807200505092011";


WiFiClient client;
HTTPClient http;

void setup() {

  // put your setup code here, to run once:
  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting...");
  }

}

void loop() {
  if (WiFi.status() == WL_CONNECTED) {

    http.begin(client, "http://192.168.1.252/user/counter.json");
    int httpCode = http.GET();
    Serial.println("Connected");
    Serial.println(httpCode);
    //Check the returning code
    if (httpCode == 200) {
      Serial.println("Connected");
      String payload = http.getString();
      Serial.println("http string");
      Serial.println(payload);
      Serial.println("http string end");

    } else {
      Serial.println("Gateway Problem");
    }
    http.end();   //Close connection
  } else {
    Serial.println("NOT Connected! Check WiFi");
  }
  // Delay
  delay(1000);

}

when I trace it get

Connecting...
Connecting...
Connected
200
Connected
http string

http string end
Connected
200
Connected
http string

http string end
Connected
200
Connected
http string

Has you can see the payload is empty/blank.
Any suggestion for me?
Thanks

[Tech-TX]

This is an area for issues with the Arduino/esp8266 core files and included libraries. The issue template that you've ignored clearly states that "how do I..." questions are for the arduino.cc or esp8266.com forums, not here.
The glitter is also open to generic "how do I" questions.

[igorfelluga]

I'm in right place
I have tested with older version and with 2.7.1 everything work.
With 2.7.4 I get the blank payload.

[d-a-v]

Your code works well with current master.
What does curl -D - http://192.168.1.252/user/counter.json give ?

[igorfelluga]

I get

HTTP/1.1 200 OK
Connection: close
Content-Type: application/json
Cache-Control: no-cache

{
"logged": 0,
"domus": "000000000000",
"life": 0,
"rt_stat": 2,
"dataora": 1604830496,
"instant": ["1.23kW","","","","","","","","","","","","","","","","","","","","","","","","","","","","0W","0W",""]
}

[d-a-v]

There is no Content-Length in the header. It is usually recommended but not mandatory, after checking it is supposed to be handled in our code.
There were recent changes on ability to reuse a connection. This is maybe a so-far-unseen side effect.
We need to check.
Out of curiosity what is the server ?

[igorfelluga]

it's a gateway
https://pro.comelitgroup.com/en-gb/product/1456

[d-a-v]

I reproduced the issue and while trying to fix I realized it already is in #6979.
You can try with this pull request or you can also try the installable alpha release (v0.0.2).

[Endc89]

Hi,
I have a similar behavior to that described in this issue.

I'm sending some GET requests and reading the response with http.getString(). For all the requests I get 200 as a respose code but for some of them http.getString() return blank.

Testing requests with curl everything works properly. The big difference between the requests is the payload size, I noticed that if the payload is large http.getString() return blank. At the moment I don't know exactly after what size this behavior occurs and if really the problem is the size.

Testing requests with curl I have also identified the size of the payloads:

• requests with payloads of ~600 characters and ~2500 characters -> http.getString() ok
• requests with payloads of ~5000 characters and ~9500 characters -> http.getString() blank

Is this possible? Any suggestions?

At the moment i'm not using Content-Length because i don't know the dimensions of the answers.
I'm using Release 3.0.2

Thanks

[d-a-v]

If you can get a 9500 bytes long answer maybe this protocol should be revised ?
It'd be the best option, otherwise there are some paths:

• use a reference string if you currently don't, it will prevent from duplicating a large object

const String& payload = http.getString();

• ask core to reserve data in second heap (option must be enabled from tools menu)

ESP.setIramHeap();
const String& payload = http.getString();
ESP.resetHeap();

(check example)

• or stream data to a file (in flash or sdcard) (wear-leveling is the enemy here)