JsonHttpClient.ino

Description

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
  ]
}

Source code

// ArduinoJson - arduinojson.org
// Copyright Benoit Blanchon 2014-2018
// MIT License

#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 JsonBuffer
  // Use arduinojson.org/assistant to compute the capacity.
  const size_t capacity = JSON_OBJECT_SIZE(3) + JSON_ARRAY_SIZE(2) + 60;
  DynamicJsonBuffer jsonBuffer(capacity);

  // Parse JSON object
  JsonObject& root = jsonBuffer.parseObject(client);
  if (!root.success()) {
    Serial.println(F("Parsing failed!"));
    return;
  }

  // Extract values
  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
}

Classes used in this example

Functions used in this example

Keep learning

The chapter “Deserialize ArduinoJson” of Mastering ArduinoJson is a tutorial on deserialization, it shows how to parse the response from Yahoo Weather.

The chapter “Case Studies” shows how to parse the huge JSON documents from OpenWeatherMap and Weather Underground, with a limited amount of memory.