Code (C++)

#include <ArduinoJson.h>
#include <Ethernet.h>
#include <SPI.h>

EthernetClient client;

const char* server = "ws2.noman.it";  // server's address
const char* resource = "/api/energy/realtime/D2DC3D0FDD0129BF";                    // http resource
const unsigned long BAUD_RATE = 9600;                 // serial connection speed
const unsigned long HTTP_TIMEOUT = 10000;  // max respone time from server
const size_t MAX_CONTENT_SIZE = 512;       // max size of the HTTP response

// The type of data that we want to extract from the page
struct UserData {
  char Production[32];
  char Consumption[32];
};

// ARDUINO entry point #1: runs once when you press reset or power the board
void setup() {
  initSerial();
  initEthernet();
}

// ARDUINO entry point #2: runs over and over again forever
void loop() {
  if (connect(server)) {
    if (sendRequest(server, resource) && skipResponseHeaders()) {
      UserData userData;
      if (readReponseContent(&userData)) {
        printUserData(&userData);
      }
    }
  }
  disconnect();
  wait();
}

// Initialize Serial port
void initSerial() {
  Serial.begin(BAUD_RATE);
  while (!Serial) {
    ;  // wait for serial port to initialize
  }
  Serial.println("Serial ready");
}

// Initialize Ethernet library
void initEthernet() {
  byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
  if (!Ethernet.begin(mac)) {
    Serial.println("Failed to configure Ethernet");
    return;
  }
  Serial.println("Ethernet ready");
  delay(1000);
}

// Open connection to the HTTP server
bool connect(const char* hostName) {
  Serial.print("Connect to ");
  Serial.println(hostName);

  bool ok = client.connect(hostName, 1880);

  Serial.println(ok ? "Connected" : "Connection Failed!");
  return ok;
}

// Send the HTTP GET request to the server
bool sendRequest(const char* host, const char* resource) {
  Serial.print("GET ");
  Serial.println(resource);

  client.print("GET ");
  client.print(resource);
  client.println(" HTTP/1.0");
  client.print("Host: ");
  client.println(host);
  client.println("Connection: close");
  client.println();

  return true;
}

// Skip HTTP headers so that we are at the beginning of the response's body
bool skipResponseHeaders() {
  // HTTP headers end with an empty line
  char endOfHeaders[] = "\r\n\r\n";

  client.setTimeout(HTTP_TIMEOUT);
  bool ok = client.find(endOfHeaders);

  if (!ok) {
    Serial.println("No response or invalid response!");
  }

  return ok;
}

bool readReponseContent(struct UserData* userData) {
  // Compute optimal size of the JSON buffer according to what we need to parse.
  // See https://bblanchon.github.io/ArduinoJson/assistant/
const size_t bufferSize = JSON_ARRAY_SIZE(1) + JSON_OBJECT_SIZE(13) + 260;
DynamicJsonBuffer jsonBuffer(bufferSize);

JsonArray& root = jsonBuffer.parseArray(client);

JsonObject& root_0 = root[0];

  if (!root.success()) {
    Serial.println("JSON parsing failed!");
    //  Serial.println(client);
    return false;
  }

  // Here were copy the strings we're interested in
  strcpy(userData->Production, root_0["Production"]);
  strcpy(userData->Consumption, root_0["Consumption"]);
  // It's not mandatory to make a copy, you could just use the pointers
  // Since, they are pointing inside the "content" buffer, so you need to make
  // sure it's still in memory when you read the string

  return true;
}

// Print the data extracted from the JSON
void printUserData(const struct UserData* userData) {
  Serial.print("Production = ");
  Serial.println(userData->Production);
  Serial.print("Consumption = ");
  Serial.println(userData->Consumption);
}

// Close the connection with the HTTP server
void disconnect() {
  Serial.println("Disconnect");
  client.stop();
}

// Pause for a 5 seconds
void wait() {
  Serial.println("Wait 5 seconds");
  delay(5000);
}
 

Code (C++)

float produzione = root_0["Production"];