Thing-IF SDK Structure

Thing-IF SDK provides the Thing-IF SDK for C for implementing a program that runs on things (devices) and the Thing-IF SDK for Android, iOS, and JavaScript for implementing mobile apps.

By leveraging both thing and mobile app SDKs, you can build services that enable users to manipulate the things from the mobile apps.

Thing-IF SDK for C

The Thing-IF SDK for C is a C program that runs on the things. The source code is open to the public. You can download and build it for your environment to start your development.

SDK Structure

The following diagram illustrates the SDK structure.

The SDK is composed of three repositories: thing-if-ThingSDK, KiiThingSDK-Embedded, and kii_json. Your code will leverage them to make use of the Thing Interaction Framework features.

Here are several important points you need to be aware of when using the Thing SDK:

  • You basically need only to implement the handlers

    After your program initializes the SDK, it basically waits for the SDK to execute its callback functions (i.e., command handler and state handler).

  • The SDK internally uses the Thing SDK Embedded

    The Thing-IF SDK internally uses the Thing SDK Embedded, which is an SDK written in C for embedded devices. This SDK supports key functionalities of the Kii Cloud SDK.

    You can also use the Thing SDK Embedded directly. See Implementing Things with Thing SDK Embedded for more information. See Using kii-core to learn how to use kii-core, which is internally used in the Thing SDK Embedded.

  • All OS-related functions are ready for use.

    The thing-if-ThingSDK defines the reference implementation for some specific environments. The APIs that are deeply dependent on the OS, like Socket and Task management, are already defined in the reference implementation. You can simply build it to use the functions. If you want to use the SDK in other environments, you need to provide equivalent functions for the environment by referring the source code.

    In the actual implementation, the thing-if-ThingSDK is integrating various OS dependent libraries that are included in the KiIThing-Embedded.

  • MQTT implementation is ready for use

    The KiiThingSDK-Embedded contains the implementation of the MQTT client, so that you can leverage the MQTT push notification without any additional library. In your code, you will use the push notification for receiving commands.

  • You need to prepare buffers in your program.

    Your thing program needs to allocate memory for receiving commands and sending states. The allocated memory is passed to the SDK upon the initialization. The API for allocating memory from the heap (something equivalent to malloc) is not available in the SDK.

    See Initializing and Onboarding for more details on the buffer handling.

  • The kii_json library is available for parsing JSON.

    When integrating with the mobile app, the thing needs to parse the JSON string.

    You can use any implementation for parsing JSON string, but you will be able to keep your code simple by using the kii_json library in your program. See Parsing JSON for more details.

  • The library will handle the communication control

    The library in the thing-if-ThingSDK implements and controls socket API calls for each OS. The implementations of the basic socket APIs such as connect(), close(), send(), and recv() are isolated from the caller, so you can customize their implementations for your target environment and leverage the SSL/TLS connection.

    The library also implements the reconnection logic; it will reestablish a new connection when the connection is lost while waiting for a command to be sent from the server via an MQTT channel.

Reference Implementation

We are providing the reference implementation for the following environment:

  • Linux
  • Intel Edison
  • Ti CC3200

If you want to use the SDK in other environments, please implement the necessary APIs by yourself. As shown in the structure diagram, all OS dependent processes like Socket and Task (thread) generation are pluggable for each platform. You can deploy the SDK to any platforms by replacing these implementations.

If you are replacing the API implementations, please prepare the source code equivalent to kii_iot_environment_linux.c file in the thing-if-ThingSDK repository for your environment.

See here for more details on the SDK preparation.

Thing-IF SDK for Mobile Apps

We offer SDKs for building mobile apps which work with Thing Interaction Framework. These SDKs support development of native apps for Android and iOS and web apps with JavaScript and TypeScript. With these SDKs, you can easily develop mobile apps for manipulating the things.

The supported environments are covered in SDKs and Supported Environments.

To use the Thing-IF SDK, you also need to use the Kii Cloud SDK.

  • Thing-IF SDK offers the ability to manipulate things, like sending commands and reading state.

  • Kii Cloud SDK provides the ability to get the access token and ID of the user who will own the thing. The access token and ID are needed when you are to initialize the thing.

The Thing Interaction Framework internally uses the Kii Cloud features (e.g., user and data management, push notifications) to realize the command and state transfer. We will present how to implement such features in the development guides. For the typical mobile app, here, you will just need to execute Kii Cloud SDK features just like the provided samples.

Kii Cloud and Thing Interaction Framework share the same application on the cloud. If you want to use features such as data management and push notifications, you can also call the function of the Kii Cloud SDK.

See the related topics in the development guides for Android, iOS, and JavaScript for more details on how to install the SDK.


You can directly use the REST API commands instead of the above SDKs to develop mobile apps or things for a solution with Thing Interaction Framework.

Especially, if you use functions within Thing Interaction Framework, you can develop things with the MQTT protocol only. See Using API via MQTT and Implementation with MQTT Only to learn how to implement things with the MQTT protocol only.