Building Bridges

KDE developers have been working for more than a year to extend KDE Plasma to the mobile world. The current project, under the name Plasma Mobile, is geared to provide a free platform for mobile devices some time in the future, thus acting as an alternative to existing platforms [1]. Since Google Summer of Code 2015 (GSoC 015), an application has connected Android and BlackBerry devices with the Plasma desktop and supported some reciprocal functional control.

Spanish developer Albert Vaca aptly dubbed the application KDE Connect [2], which is available for Linux and FreeBSD, with clients for Android and BlackBerry. An iOS version is currently being built, as well. Users can meaningfully connect PCs, notebooks, tablets, and smartphones on the home network. Additionally, extensions for Firefox [3] and Chrome [4] send URLs from the desktop to Android devices. With the kdeconnect-cli command, you can control KDE Connect in a terminal (Figure 1).

Figure 1: KDE Connect from a terminal with kdeconnect-cli.

In September 2016, KDE Connect reached version 1.0, which incorporates several important innovations. Most distributions are not packaging this version right now, but that is likely to change in the near future. The associated packages in the archives of the distributions are typically named kdeconnect; for Ubuntu – depending on the version – this is kdeconnect-kde or kdeconnect-plasma. If necessary, you can build the latest 1.0.1 version from source code.

Ubuntu, Linux Mint, and Elementary OS can use KDE Connect with desktop environments like Gnome, Cinnamon, Unity, Maté, Xfce, and LXDE/LXQt. In these cases, you install using the indicator-kdeconnect personal package archive (PPA) [5].

To install the Android app, go to either F-Droid or the Google Play Store. You need at least Android 4.1 (Jelly Bean) to use all the features. If you have a firewall, you need to open ports 1714 to 1764 for both TCP and UDP. To integrate the data of the mobile device with the desktop file manager, you also need the sshfs package.

Getting Started

After installing KDE Connect on all the devices to be connected, you should launch the Android app. From there you can pair the devices, much like you would using Bluetooth (Figure 2). Instead of Bluetooth, D-Bus, its Media Player Remote Interfacing Specification (MPRIS) [6] interface, and the Avahi Zeroconf implementation [7] connect the devices. The MPRIS interface provides an API for controlling media players, including functions for identifying, querying, and play.

Figure 2: In the Android app, pair your mobile device with the desktop.

The app offers to ping the respective device to test the connection; then, you can use the three-item menu at top right to enable the desired plugins. On the Plasma desktop, you will want to install the plasmoid for KDE Connect first, so you always have quick access to the application (Figure 3).

Figure 3: A plasmoid gives direct access to all the KDE Connect features.

Key Features

You can now right-click on the KDE Connect plasmoid to access the configuration on your desktop (Figure 4) and enter the following settings:

• Battery monitor: Display and warn in case of low battery power.
• Receive notifications: Forward notifications on the mobile device to the desktop.
• Remote filesystem browser: Browse the remote file system with SSH Filesystem (SSHFS).
• Pause media during calls: Stop music or movies in case of a call.
• Multimedia control receiver: Remote control for media running on the desktop.
• Telephony integration: Send alerts for calls and text messages to the desktop.
• Share and receive: Send files from the mobile device to the desktop.
• Remote input: Use the smartphone as a touchpad or keyboard for the desktop.
• Clipboard: Share the clipboard with other devices.

Figure 4: Right-clicking on the KDE Connect plasmoid calls the configuration on the desktop.

In the lab test, I quickly switched off the notifications from the mobile device to the desktop, because the number of messages was annoying.

In version 1.0, KDE Connect saw the introduction of some long-awaited features. For example, you not only see a notification for incoming text messages on the desktop, you can also respond directly; conversely, the mobile device now receives notifications from the desktop. You can also define commands to the desktop, which you can then call from the mobile device. In this way, for example, you could send a notebook to sleep. Security benefits with the switch from RSA keys to TLS for encryption, ensuring that no external devices can hijack the connection.

One of the most popular features includes pausing music or movie applications, such as Amarok (Figure 5), Clementine, VLC, or SMPlayer, when a call comes in on the smartphone. After the end of the call, the respective media continue to run. Integration with a file manager like Dolphin, Nemo, Nautilus, or Thunar is one of the much-used functions. You can use SSHFS to display the contents of the mobile device on the desktop or copy and move (using drag and drop). Dolphin automatically integrates mobile devices (Figure 6); in other file managers, you need to add them manually.

Figure 5: If necessary, you can use KDE Connect to control the desktop via the mobile device.

Figure 6: You can use SSHFS to display content or copy and move mobile device items from the desktop.

From the file manager, you can send a larger number of images for editing to the desktop quickly. This removes the need for apps like AirDroid [8], and the data does not leave the home network. Sending data, images, or URLs from the mobile device works in the respective share pages in the corresponding applications (Figure 7); transmitted pictures or data are displayed on the desktop and URLs are opened in the browser. The battery indicator on the desktop for the mobile device is very useful, as well.

Figure 7: Sending data, images, or URLs from the mobile device to the desktop relies on the respective share pages in the corresponding applications.

The exchange of clipboard content keeps the clipboards of all connected devices synchronized in real time. However, the function is dangerous when you are outside the home LAN or a secure network, because the clipboard could contain sensitive data such as passwords that you do not want to share with others (e.g., at the workplace).

Conclusions

KDE Connect is literally addictive. It sets up a secure bridge over the short distance between the Plasma desktop and mobile platforms such as Android, BlackBerry, and iOS. The carefully considered application incorporates several features – especially for the KDE desktop – to which you become accustomed after just a short time. The software is stable and constantly evolving. I can therefore wholeheartedly recommend KDE Connect for the Plasma desktop. Users of other desktop environments have to decide whether they want to accept the many dependencies in the form of KDE packages to access the abundance of features in KDE Connect.