ArduinoJson/examples/JsonHttpClient/JsonHttpClient.ino

// ArduinoJson - arduinojson.org
// Copyright Benoit Blanchon 2014-2018
// MIT License
//
// This example shows how to parse a JSON document in an HTTP response.
// It uses the Ethernet library, but can be easily adapted for Wifi.
//
// It performs a GET resquest on arduinojson.org/example.json
// Here is the expected response:
// {
//   "sensor": "gps",
//   "time": 1351824120,
//   "data": [
//     48.756080,
//     2.302038
//   ]
// }

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

void setup() {
  // Initialize Serial port
  Serial.begin(9600);
  while (!Serial) continue;

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

  Serial.println(F("Connecting..."));

  // Connect to HTTP server
  EthernetClient client;
  client.setTimeout(10000);
  if (!client.connect("arduinojson.org", 80)) {
    Serial.println(F("Connection failed"));
    return;
  }

  Serial.println(F("Connected!"));

  // Send HTTP request
  client.println(F("GET /example.json HTTP/1.0"));
  client.println(F("Host: arduinojson.org"));
  client.println(F("Connection: close"));
  if (client.println() == 0) {
    Serial.println(F("Failed to send request"));
    return;
  }

  // Check HTTP status
  char status[32] = {0};
  client.readBytesUntil('\r', status, sizeof(status));
  if (strcmp(status, "HTTP/1.1 200 OK") != 0) {
    Serial.print(F("Unexpected response: "));
    Serial.println(status);
    return;
  }

  // Skip HTTP headers
  char endOfHeaders[] = "\r\n\r\n";
  if (!client.find(endOfHeaders)) {
    Serial.println(F("Invalid response"));
    return;
  }

  // Allocate the JSON document
  // Use arduinojson.org/assistant to compute the capacity.
  const size_t capacity = JSON_OBJECT_SIZE(3) + JSON_ARRAY_SIZE(2) + 60;
  DynamicJsonDocument doc(capacity);

  // Parse JSON object
  DeserializationError error = deserializeJson(doc, client);
  if (error) {
    Serial.print(F("deserializeJson() failed: "));
    Serial.println(error.c_str());
    return;
  }

  // Extract values
  JsonObject root = doc.as<JsonObject>();
  Serial.println(F("Response:"));
  Serial.println(root["sensor"].as<char*>());
  Serial.println(root["time"].as<char*>());
  Serial.println(root["data"][0].as<char*>());
  Serial.println(root["data"][1].as<char*>());

  // Disconnect
  client.stop();
}

void loop() {
  // not used in this example
}

// Visit https://arduinojson.org/v6/example/http-client/ for more.