problem of serializeJson in ArduinoJson 6 with ESP8266 WiFiClientSecure

Created by: liuzheng1990

Hi, I'm using ArduinoJson to compose the body of HTTPS requests. I've got some problem when trying to serialize the json document to WiFiClientSecure object. Here are some sample codes. I'm using ArduinoJson 6.10.0 with ESP8266 Arduino core board both 2.4.2 and 2.5.0. Roughly the same error message appeared.

#include <ESP8266WiFi.h>
#include <ArduinoJson.h>
#include <WiFiClientSecure.h>
#include <WiFiClient.h>

#define HOSTNAME <my cloud server's IP>
#define PORT 443
#define FINGER_PRINT <self-signed cert's fingerprint>

WiFiClientSecure http;
// WiFiClient http; // when change to WiFiClient, it compiled.

void setup() {
  // put your setup code here, to run once:
  WiFi.begin(<wifi_ssid>, <wifi_password>);
  Serial.begin(115200);
  Serial.println();
  Serial.print("Connecting to WiFi");
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(".");
    delay(500);
  }
  Serial.println();
  Serial.print("WiFi connection established! IP: "); Serial.println(WiFi.localIP());
}

void loop() {
  if (!http.connect(HOSTNAME, PORT))
  {
    Serial.println(F("WiFiManagerError: Failed to connect to the server!"));
    http.stop();
    delay(5000);
    return;
  }

/* need to comment the fingerprint verification if using WiFiClient */
  if (!http.verify(FINGER_PRINT, HOSTNAME)) 
  {
    Serial.println(F("WiFiManagerError: SSL certificate does not match!"));
    http.stop();
    delay(5000);
    return;
  }


  StaticJsonDocument<200> jdoc;
  jdoc["user_id"] = "Alice";
  jdoc["age"] = 26.5;
  
  http.print("POST"); http.print(" "); http.print("/"); http.println(" HTTP/1.1");
  http.print("HOST: "); http.println(HOSTNAME);
  http.println("User-Agent: haiyan");
  jdoc["device_id"] = "nbzheng";
  size_t len = measureJson(jdoc);
  http.println("Content-Type: application/json");
  http.print("Content-Length: "); http.println(len);
  http.println("Connection: close");
  http.println();
  serializeJson(jdoc, http);
}

Here is the error message:

In file included from /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:10:0, from /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson.hpp:34, from /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson.h:9, from /home/bear/DataBank/codelab/arduino_lab/wifi_tutorial/json_wificlientsecure/json_wificlientsecure.ino:2: /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp: In instantiation of 'void ArduinoJson6100_000::TextFormatter::writeRaw(char) [with TWriter = axTLS::WiFiClientSecure]': /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:58:19: required from 'void ArduinoJson6100_000::TextFormatter::writeFloat(T) [with T = float; TWriter = axTLS::WiFiClientSecure]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:56:5: required from 'void ArduinoJson6100_000::JsonSerializer::visitFloat(ArduinoJson6100_000::Float) [with TWriter = axTLS::WiFiClientSecure; ArduinoJson6100_000::Float = float]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Variant/VariantData.hpp:29:51: required from 'void ArduinoJson6100_000::VariantData::accept(Visitor&) const [with Visitor = ArduinoJson6100_000::JsonSerializeraxTLS::WiFiClientSecure]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Variant/VariantFunctions.hpp:14:5: required from 'void ArduinoJson6100_000::variantAccept(const ArduinoJson6100_000::VariantData*, Visitor&) [with Visitor = ArduinoJson6100_000::JsonSerializeraxTLS::WiFiClientSecure]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Variant/VariantRef.hpp:351:33: required from 'void ArduinoJson6100_000::VariantConstRef::accept(Visitor&) const [with Visitor = ArduinoJson6100_000::JsonSerializeraxTLS::WiFiClientSecure]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Document/JsonDocument.hpp:21:39: required from 'void ArduinoJson6100_000::JsonDocument::accept(Visitor&) const [with Visitor = ArduinoJson6100_000::JsonSerializeraxTLS::WiFiClientSecure]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Serialization/serialize.hpp:21:3: required from 'typename ArduinoJson6100_000::enable_if<(! ArduinoJson6100_000::IsWriteableString::value), unsigned int>::type ArduinoJson6100_000::serialize(const TSource&, TPrint&) [with TSerializer = ArduinoJson6100_000::JsonSerializer; TSource = ArduinoJson6100_000::StaticJsonDocument<200u>; TPrint = axTLS::WiFiClientSecure; typename ArduinoJson6100_000::enable_if<(! ArduinoJson6100_000::IsWriteableString::value), unsigned int>::type = unsigned int]' /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:102:55: required from 'size_t ArduinoJson6100_000::serializeJson(const TSource&, TDestination&) [with TSource = ArduinoJson6100_000::StaticJsonDocument<200u>; TDestination = axTLS::WiFiClientSecure; size_t = unsigned int]' /home/bear/DataBank/codelab/arduino_lab/wifi_tutorial/json_wificlientsecure/json_wificlientsecure.ino:58:27: required from here /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:136:13: error: no matching function for call to 'axTLS::WiFiClientSecure::write(uint8_t)' _length += _writer.write(static_cast<uint8_t>(c)); ^ /home/bear/Arduino/libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:136:13: note: candidates are: In file included from /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/WiFiClientSecure.h:23:0, from /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/ESP8266WiFi.h:42, from /home/bear/DataBank/codelab/arduino_lab/wifi_tutorial/json_wificlientsecure/json_wificlientsecure.ino:1: /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.h:46:10: note: virtual size_t axTLS::WiFiClientSecure::write(const uint8_t*, size_t) size_t write(const uint8_t *buf, size_t size) override; ^ /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.h:46:10: note: candidate expects 2 arguments, 1 provided /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.h:48:10: note: size_t axTLS::WiFiClientSecure::write(Stream&) size_t write(Stream& stream); // Note this is not virtual ^ /home/bear/.arduino15/packages/esp8266/hardware/esp8266/2.4.2/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.h:48:10: note: no known conversion for argument 1 from 'uint8_t {aka unsigned char}' to 'Stream&' exit status 1 Error compiling for board NodeMCU 1.0 (ESP-12E Module).

Sorry it's a bit long and messy. I think it's a type conversion problem. When WiFiClientSecure is replaced by WiFiClient for HTTP POST, not HTTPS, it compiled. In addition, when I used ArduinoJson 5, it worked without problems. I do like the JsonDocument instead of JsonBuffer and still wants to know how to solve this problem in ArduinoJson 6.

Is there anything I missed? Thanks very much for your help!

Best Zheng