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Installing the C++ SDK

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Linux

To install the C++ SDK:
1

Fetch and extract the Ditto package. (Downloading and Unpacking Ditto)
2

Configure your app to link to the Ditto library. (Linking to Ditto)

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Downloading and Unpacking Ditto

Download Ditto.tar.gz and unpack an archive containing the libditto.a static library and Ditto header: 
curl -O https://software.ditto.live/cpp-linux-x86_64/Ditto/4.11.0/dist/Ditto.tar.gz && tar xvfz Ditto.tar.gz

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Linking to Ditto

Add -lditto as a compilation step in the main.cpp source file:
For instructions on adding cross-platform Bluetooth Low Energy (LE) capabilities, see Bluetooth on Linux.BlueZ is the official Bluetooth protocol stack implementation for Linux systems to communicate with other Bluetooth-enabled platforms.
# This command assumes:
# You have unzipped the Ditto.tar.gz in a relative directory ./sdk/
# Your main code entry point is in ./src/main.cpp

g++ -std=c++17 ./src/main.cpp -I ./sdk -lditto -ldl -lrt -pthread -L ./sdk -o dist/main;

 # Once executed, your output will be available at: ./dist/main

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Android

The Ditto C++ SDK for Android is available in the Maven Central repository: https://central.sonatype.com/artifact/live.ditto/ditto-cpp Integrating the C++ SDK into an Android app requires use of the Android Native Development Kit (NDK) and the Java Native Interface (JNI) mechanism. To learn more about the NDK and JNI, see https://developer.android.com/ndk/guides.

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Setting Up Your Environment

Include the Maven Central repository in your Gradle file, and then synchronize it with your project.
1

From your project-level build.gradle file located in the app’s root directory, ensure the mavenCentral() repository is included in the repositories section:
Gradle
allprojects {
  repositories { mavenCentral() }
}
2

Synchronize your project with the Gradle file by clicking File > Sync Project with Gradle Files.

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Adding the Ditto SDK Dependency

Add the Ditto SDK to your app’s build.gradle file in the dependencies block with the appropriate version: 
implementation "live.ditto:ditto-cpp:4.9.3"
To ensure that your app links properly with the shared objects in the SDK, and that your app has debugging symbols for the SDK, add these rules to your android packagingOptions block: 
        jniLibs {
            useLegacyPackaging = true
            keepDebugSymbols.add("**/*.so")
            pickFirsts.add("lib/**/libditto.so")
            pickFirsts.add("lib/**/libc++_shared.so")
        }

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Setting Android Context

The C++ SDK for Android requires that the app call Ditto::set_android_context(JNIEnv* env, jobject context) with an application context object after creating an instance of the C++ Ditto class. This context is required by the SDK on Android to access system resources such as network interfaces and files.

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Configuring Permissions

The Android operating system limits access to some device functionality for end-user control and privacy. In order to use this functionality, configure your app to declare and request permissions from end users at runtime:
1

Review permissions used by Ditto. (Declaring Permissions)
2

Proactively check permission status to avoid unnecessary delay between granting access and Ditto being able to use the feature. (Requesting Permissions)

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Declaring Permissions in the Android Manifest

Android requires certain permissions to be explicitly requested by the app to access features like Bluetooth Low Energy and Wi-Fi Aware. These permissions must be declared in the app’s manifest file and requested from the end user at runtime. The Ditto SDK’s AndroidManifest.xml includes all of the necessary permissions for enabling its mesh network capabilities. These permissions will automatically be merged with your app’s permissions, so you should be aware of them. 

<!-- Required for Bluetooth -->
<uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" tools:targetApi="31" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" tools:targetApi="31" />
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" tools:targetApi="31" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="28" />

<!-- Required for WiFi Aware -->
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.NEARBY_WIFI_DEVICES" android:usesPermissionFlags="neverForLocation" tools:targetApi="33" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" android:maxSdkVersion="32" />

<!-- Required for WiFi Aware, TCP, UDP, and WebSockets -->
<uses-permission android:name="android.permission.INTERNET" />

<!-- Required for mDNS discovery -->
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
Some of these permissions have an android:maxSdkVersion attribute which means they are not used on devices running newer versions of Android. This is a best practice to respect users’ privacy when those permissions are not necessary. However, some apps may still need to use one or more of the above permissions across more versions of Android. This can be accomplished by overriding the permission configuration in your app’s AndroidManifest.xml. To override any of these permission limitations in your app, do the following:
1

Open the AndroidManifest.xml located in the app/src/main directory of your project.
2

Within the same manifest tag, just before the application tag, add the relevant permissions you want to configure (location example):
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" tools:remove="android:maxSdkVersion" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" tools:remove="android:maxSdkVersion" />
Note the additional tools:remove attribute. This tells the manifest merger to selectively remove the android:maxSdkVersion behavior from the associated permissions, changing them to apply to all Android versions.
For more information, see the official Permissions on Android and Merge manifest files documentation.

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Requesting Permissions at Runtime

At runtime, your app can call the C++ Ditto::missing_permissions() function to get a list of permissions required by Ditto that are missing, and your app can request them.

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Declaring a Foreground Service (Optional)

A foreground service allows your app to continue syncing data with Ditto while running in the background. A foreground service is not required to use Ditto, but without it your app will stop syncing whenever it is in the background. To declare the foreground service, add the following to your AndroidManifest.xml: 
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_CONNECTED_DEVICE" tools:targetApi="upside_down_cake" />
<uses-permission android:name="android.permission.POST_NOTIFICATIONS" tools:targetApi="tiramisu" />

<application ...>
    <service
        android:name="live.ditto.transports.foregroundservice.DefaultDittoForegroundService"
        android:exported="false"
        android:foregroundServiceType="connectedDevice"
        android:stopWithTask="true">
        <meta-data android:name="notificationChannelName" android:value="Background Data Sync" />
        <meta-data android:name="notificationChannelId" android:value="BackgroundDataSyncId" />
        <meta-data android:name="smallIcon" android:resource="@drawable/small_app_icon" />
        <meta-data android:name="notificationTitle" android:value="Syncing Data" />
        <meta-data android:name="notificationText" android:value="Syncing data across connected devices" />
        <meta-data android:name="notificationId" android:value="1001" />
    </service>
</application>
Make sure you customize the service metadata—it will be displayed to the user in the foreground service notification. Note that your small_app_icon drawable must be monochrome white. The foreground service will be automatically started and stopped on startSync() and stopSync(), respectively.

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Importing and Initializing Ditto

From the source code of your app, using #include <Ditto.h>, use the ditto namespace, and provide your access credentials:
C++

const auto identity = ditto::Identity::OnlinePlayground(
    std::move(app_id),
    std::move(online_playground_token),
    enable_cloud_sync,                  // This is required to be set to false to use the correct URLs
    std::move(custom_url)
);

ditto->update_transport_config([&](ditto::TransportConfig &config) {
    config.enable_all_peer_to_peer();
    config.connect.websocket_urls.insert(websocket_url);
});
// Required for compatibility with DQL.
ditto->disable_sync_with_v3();

// Disable DQL strict mode so that collection definitions are not required in DQL queries
ditto->get_store().execute("ALTER SYSTEM SET DQL_STRICT_MODE = false");

ditto->start_sync();