Cannot connect to the RGeomViewer/THttpEngine

ROOT
1

Problem

In the ROOT interpreter:

auto viewer = new ROOT::RGeomViewer();
viewer->Show();
Info in <THttpEngine::Create>: Starting HTTP server on port 127.0.0.1:9478
//go to browser and try to open the IP address. Returns 404.

Expected

I should be able to access the viewer from the browser

Notes

Maybe I am missing some dependency, or network setup, which is necessary for it to work?
I have tried to listen on the port and send there stuff wiith netcat and it works.

Launching the server in the ROOT interpreter also works without issues:

auto serv = new THttpServer("http:9479");

ROOT Version: 6.38.00
Platform: Alma9
Browser: Mozilla Firefox 140.9
Env:

source /cvmfs/sw-nightlies.hsf.org/key4hep/setup.sh -r 2026-04-09
2

Hi,

Which browser is installed on your machine?
Can you check content of $ROOTSYS/etc/system.rootrc file:

 cat $ROOTSYS/etc/system.rootrc | grep WebGui.
# WebGui specific settings (defaults are shown)
WebGui.HttpPort:            0
WebGui.HttpPortMin:         8800
WebGui.HttpPortMax:         9800
WebGui.HttpBind:
WebGui.HttpLoopback:        yes
WebGui.OnetimeKey:          yes
WebGui.SingleConnMode:      yes
WebGui.UseHttps:            no
WebGui.ServerCert:          rootserver.pem
WebGui.WaitForTmout:        100.0
WebGui.Chrome:             /usr/bin/chromium
WebGui.ChromeVersion:      145
WebGui.Edge:               
WebGui.Firefox:            /usr/bin/firefox
#WebGui.RootUi5Path:        $(ROOTSYS)/ui5

or just in ROOT session:

root [1] gEnv->GetValue("WebGui.Chrome","")
(const char *) "/usr/bin/chromium"
root [2] gEnv->GetValue("WebGui.Firefox","")
(const char *) "/usr/bin/firefox"

Are you working on the local desktop or on remote node?
In last case you may try to rootssh utility - see some info here.

Regards,
Sergey

3

Hi @linev,

I am using local desktop.
My browser is Firefox 140.9

File $ROOTSYS/etc/system.rootrc doesn’t seem to exist in my case.

ls: cannot access '/cvmfs/sw-nightlies.hsf.org/key4hep/releases/2026-02-26/x86_64-almalinux9-gcc14.2.0-opt/root/6.38.00-lovp3j/etc/system.rootrc': No such file or directory

Both gEnv->GetValue("WebGui.Chrome","") and gEnv->GetValue("WebGui.Firefox","") return empty strings.

which firefox
/usr/bin/firefox
4

cat $(root-config --etcdir)/system.rootrc | grep WebGui

1 Like
5 
# WebGui specific settings (defaults are shown)
WebGui.HttpPort:            0
WebGui.HttpPortMin:         8800
WebGui.HttpPortMax:         9800
WebGui.HttpBind:
WebGui.HttpLoopback:        yes
WebGui.OnetimeKey:          yes
WebGui.SingleConnMode:      yes
WebGui.UseHttps:            no
WebGui.ServerCert:          rootserver.pem
WebGui.WaitForTmout:        100.0
WebGui.Chrome:             
WebGui.ChromeVersion:      
WebGui.Edge:               
WebGui.Firefox:            
#WebGui.RootUi5Path:        /cvmfs/sw-nightlies.hsf.org/key4hep/releases/2026-02-26/x86_64-almalinux9-gcc14.2.0-opt/root/6.38.00-lovp3j/share/root/ui5
6

Hi,

Seems to be your ROOT installation did not recognize existing browsers during compilation.

You can try to start root --web=firefox. In such case ROOT tries to search firefox executable again.

Regards,
Sergey

7

Then I get seg. fault:

04:45:19 foxwise@fox01 ~ → root --web=firefox
   ------------------------------------------------------------------
  | Welcome to ROOT 6.38.00                        https://root.cern |
  | (c) 1995-2025, The ROOT Team; conception: R. Brun, F. Rademakers |
  | Built for linuxx8664gcc on Feb 26 2026, 09:18:25                 |
  | From tags/6-38-00@6-38-00                                        |
  | With g++ (Spack GCC) 14.2.0 std202002                            |
  | Try '.help'/'.?', '.demo', '.license', '.credits', '.quit'/'.q'  |
   ------------------------------------------------------------------

root [0] auto viewer = new ROOT::RGeomViewer()
(ROOT::RGeomViewer *) 0x3a506f0
root [1] viewer->Show()
Info in <THttpEngine::Create>: Starting HTTP server on port 127.0.0.1:9760
root [2] /cvmfs/sw-nightlies.hsf.org/key4hep/releases/2026-02-26/x86_64-almalinux9-gcc14.2.0-opt/root/6.38.00-lovp3j/etc/root/runfirefox.sh: line 52: 15110 Segmentation fault      (core dumped) $firefox $args > /dev/null 2> /dev/null

root [2] 

``
8

Can you provide stack trace of your seg fault.

Did you try out example from tutorials:

 root --web=firefox tutorials/visualisation/geom/web_cms.cxx