Arduino / C++ Library

The ArduinoIoTCloud library allows you to connect to the Arduino Cloud using Arduino/C++.

The default Arduino / C++ library for the Arduino Cloud is the ArduinoIoTCloud library. This library depends on the Arduino_ConnectionHandler library which provides connection via various wireless protocols (Wi-Fi®, LoRaWAN®, NB-IoT, GSM, Ethernet).

The library is integrated into the Arduino Cloud platform, where Automatic Sketch Generation converts your Thing configurations into a set files that relies on aforementioned libraries.

The ArduinoIoTCloud library supports either connection via TCP/IP or LoRaWAN®. Depending on the device you compile for, the library automatically chooses the right configuration.


To view the source code and report issues, follow the links below to the GitHub repository:

Connection Methods

The ArduinoIoTCloud library supports both connection via TCP/IP and via LoRaWAN®, which is enabled via the

classes. Depending on what device you configure, the library will automatically choose the right class, which will externally be available in your sketch file as


When connecting via TCP/IP stack, the library communicates with the Arduino Cloud via MQTT, a lightweight network protocol using a publish/subscribe method to send data. This support is enabled in the following files:


When connecting via LoRaWAN®, data is sent via The Things Network, which is integrated with the Arduino Cloud. This support is enabled in the following files:

Library API Docs

The documentation lives in the ArduinoIoTCloud library documentation page. Here you will find all public methods that are available.

Most of its functions are already pre-configured in your sketch files, so for most use cases you will not need to explore the API. Functions for connecting to, and syncing data with the Arduino Cloud is handled automatically, and will be generated into your sketch files in the web environment.

Arduino IDE (Offline)

This library can be used with the offline version of the Arduino IDE (download through the Arduino Downloads Page). You can program your devices offline and monitor them via the Cloud, but your Thing configuration is not synchronized if you do so.

To use it offline, you will manually need to install the following libraries in the Arduino IDE:

Events & Callbacks

Arduino Cloud has support for events and callbacks. This can be used to trigger specific functionalities depending on what state your device is in.

You can for example trigger a specific block of code whenever the board is in a connecting, synchronized or disconnected state. In this document, we will explore how to set it up, using an example from the ArduinoIoTCloud library.



enumeration class has three possible events:

    (0) - Board successfully connects to Arduino Cloud.
  • SYNC
    (1) - Data is successfully synced between Board and Arduino Cloud.
    (2) - Board has lost connection to Arduino Cloud.


events can occur even though no variable is created inside the Thing. However,
requires a variable to be created, as this triggers whenever data is synchronized between the board and Cloud.

These events can be subscribed to using the

function, which is documented in the next section.


Callbacks can be added for each event, and essentially triggers a custom function whenever the event occurs.

Callbacks are added via the

method from the
class, where the event and custom function are added as parameters.

1ArduinoCloud.addCallback(ArduinoIoTCloudEvent::CONNECT, doThisOnConnect);

The above code will trigger the

function whenever the
event occurs.

Please note that callback functions should be added inside the

of your sketch.

Full Example

The example below demonstrates how to use events & callbacks in the Arduino Cloud.

Code Source on Github

Suggested changes

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The Arduino documentation is licensed under the Creative Commons Attribution-Share Alike 4.0 license.