Gazebo GUI stuck at "requesting list of world names" – server not responding (Ubuntu 22.04, ROS 2 Humble)

[jainchaitanya19]

Hello,
I’m experiencing an issue where Gazebo’s GUI never loads and stays stuck on the message:

“Gazebo GUI requesting list of world names. The server may be busy downloading resources. Please be patient.”

Even after waiting several minutes, the simulation does not start, and the world is not displayed.

System Information:

OS: Ubuntu 22.04 (Jammy)

ROS 2 distro: Humble

Gazebo version: Fortress (Ignition Gazebo 6.17.0)

Graphics: Mesa Intel(R) Xe Graphics (TGL GT2)

Rendering backends installed: libignition-rendering6-ogre1, libignition-rendering6-ogre2

Steps to Reproduce:

Installed Gazebo Fortress via:

sudo apt install ignition-fortress

Ran:

ign gazebo ~/worlds/empty.world

The GUI window opens but remains stuck showing:

Gazebo GUI requesting list of world names. The server may be busy downloading resources.

What I’ve Tried:

Running with verbose mode (-v 4)

Running server-only mode (ign gazebo -s)

Reinstalling gazebo, ros-gz-sim, and ignition rendering dependencies

Verified OpenGL rendering (glxinfo shows Mesa Intel Xe Graphics working correctly)

Checked that ign and gz binaries are accessible in /usr/bin/

Expected Behavior:

Gazebo GUI should connect to the server and display the simulation world (e.g., empty.world).

Actual Behavior:

GUI hangs indefinitely at the “requesting list of world names” message.

Additional Notes:

It seems like the client GUI and the simulation server are unable to communicate locally. Any guidance on debugging or configuration checks (e.g., environment variables, port settings) would be appreciated.

[peci1]

This message is a generic message displayed until the server starts running the world. It may be displayed e.g. because model resources are being downloaded, or even in the case the server dies but GUI is running.

In general, this repo doesn't support ROS 2. There are some environment variables needed to be set for subt to work correctly, and in ROS 1, this is done by catkin. As ROS 2 doesn't support catkin, this will not work.

I suggest using the noetic branch with ROS Noetic.

[jainchaitanya19]

Hi @peci1
My project is based on ROS 2, so shifting to ROS 1 (Noetic) isn’t feasible for this work. Moreover, this issue has appeared only recently; the system was working fine before without any problems. I believe it may be an intermittent issue rather than a fundamental incompatibility.

Could we explore potential ROS 2–compatible solutions to address this?

[peci1]

Maybe there is some issue with the Fuel server? What does the followin command do?

ign fuel download -v 4 -j 8 --type model -u "https://fuel.ignitionrobotics.org/OpenRobotics/collections/SubT Tech Repo"

Please note it might not show output for quite some while, but you should at least see some nontrivial network activity happening.

[jainchaitanya19]

Hi @peci1

I tried the steps you suggested, but unfortunately the issue is still occurring.
I’ve already downloaded all the SubT models successfully — here’s a snippet from my model directory:

chaitanya@chaitanya-IdeaPad-Flex-5-14ITL05:~$ ls ~/.ignition/fuel/fuel.ignitionrobotics.org/openrobotics/models | head
4-way finals transition
4-way finals transition 2
4-way finals transition 2 lights
artifact proximity detector
barcs_qav500_sensor_config_1
barcs_qav500_sensor_config_2
base station
black and decker cordless drill
bosdyn_spot
breadcrumb node

After that, I launched Ignition Gazebo using:

ign gazebo ~/worlds/empty.world

But I’m still seeing the same behavior the GUI gets stuck at

[GUI] [Dbg] [Gui.cc:333] GUI requesting list of world names. The server may be busy downloading resources. Please be patient.

Let me know if there’s anything else I can try or check.

Thanks

[peci1]

Thanks for chiming in, @arjo129 . In this case (Fortress) it would be IGN_IP instead of GZ_IP I guess.

@jainchaitanya19 what's actually the empty.world you're trying to run? Where did you get it? What are its contents?

Also, for better debugging, run the server and GUI separately:

ign gazebo -s -v4 ~/worlds/empty.world
ign gazebo -g -v4 ~/worlds/empty.world  # in another console with the same environment