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OMNeT++ GUI in Docker

Goals¶

In another article, we have shown how to (and why) run simulations in a Docker container. However, Docker in itself is not suited to running GUI applications, so it is not ideal for developing or exploring simulations due to the unavailability of the IDE and Qtenv. In this article, we explore options to overcome this limitation.

Survey of options¶

A common way of running GUI applications in Docker is X11, a network protocol for remote graphical user interfaces. X11 requires an X11 server to be running, to which clients can connect and display their GUIs on. On Linux systems, the desktop is by default X11-based, so one doesn't need to install any extra software. On Windows and macOS, one can install a 3^rd party X11 server (for example, VcXsrv on Windows and XQuartz on macOS).

We also looked into remote desktop solutions (like VNC or RDP), where the server runs in the container, and the host connects to it as a client. Those, however, do not provide the most seamless experience, as you see a virtual desktop, not separate windows. Moreover, performance/quality might not be the best, even when running locally on the same machine. From these two, RDP seems to be more promising, as some versions support seamless mode where applications on the remote machine - in our case, inside the container - can launch separate windows on the host display. Sadly, the configuration of the RDP server is somewhat complicated.

In the future, Wayland may become a viable alternative to X11 in our use case as well. The IDE uses the GTK3 backend and Qtenv uses Qt5, and both of these widget libraries come with perfectly usable Wayland support.

Choosing the proper Docker image¶

If you want to use the GUI, you need a Docker image that contains the IDE, Qtenv, and all the libraries necessary for their operation. (Many OMNeT++ Docker images don't contain these parts, in order to keep their sizes small.)

The list of GUI-enabled OMNeT++ images is available at the following URL: https://hub.docker.com/r/omnetpp/omnetpp-gui/tags

Docker with X11¶

With the following single command you can try out OMNeT++ on any system with Docker and an X11 server on it:

docker run --rm -it -v "$(pwd):/root/models" -u "$(id -u):$(id -g)" \
  -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$DISPLAY omnetpp/omnetpp-gui:u18.04-5.5.1

The 2^nd -v option is used here to map the X11 socket into the container.

The x11docker project can be useful here. It is a collection of tricks, flags, and methods to run graphical applications in Docker (with several ways of operation, including X11 and Wayland support, GPU passthrough, all with various levels of isolation and performance, etc). x11docker allows the above command line to be simplified to:

x11docker -i -- --rm -v "$(pwd):/root/models" -- omnetpp/omnetpp-gui:u18.04-5.5.1

Feedback¶

If you found this interesting or useful, make use of the it in practice, or you have ideas on how to take it further, please let us know!