CommandPackage

CommanderModule.java

public class CommanderModule extends ReactContextBaseJavaModule {

    public CommanderModule(ReactApplicationContext reactContext) {
        super(reactContext);
    }

    @ReactMethod
    public void postCommand(ReadableMap config, Callback successCallback, Callback cancelCallback) {
        try {
            byte[] data = Olclient.postCommand(config.getString("command"));
            String dat = new String(data);
            successCallback.invoke(dat);
        } catch (Exception e) {
            cancelCallback.invoke(e.getMessage());
        }
    }

    @Override
    public String getName() {
        return "Commander";
    }
}

CommandPackage.java

public class CommandPackage implements ReactPackage {

    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
        List<NativeModule> modules = new ArrayList<NativeModule>();
        modules.add(new CommanderModule(reactContext));
        return modules;
    }

    @Override
    public List<Class<? extends JavaScriptModule>> createJSModules() {
        return Collections.emptyList();
    }

    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        return Collections.emptyList();
    }
}

MainApplication.java

public class MainApplication extends Application implements ReactApplication {

     private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {
        @Override
        public boolean getUseDeveloperSupport() {
            return BuildConfig.DEBUG;
        }

        @Override
        protected List<ReactPackage> getPackages() {
          return Arrays.<ReactPackage>asList(
                  new MainReactPackage(),
                  new CommandPackage()
          );
        }
    };

    @Override
    public ReactNativeHost getReactNativeHost() {
          return mReactNativeHost;
    }

     @Override
     public void onCreate() {
          super.onCreate();
          // React Native
          SoLoader.init(this, /* native exopackage */ false);
     }
}