SSH X11 Forwarding - GUI Crashes with X Error of failed request: BadIDChoice

Question

I am:

• Running a program on a Ubuntu 20.04 AWS instance
• Using SSH & X11 forwarding in PuTTY, with the VcXsrv X-server, to run program GUIs on my local Windows 11 machine

The GUIs of test programs like xclock/xeyes successfully run on my local machine. The issue arises when trying to run the GUI of interest (NVIDIA's Isaac Gym). I run a test script that activates the GUI. It opens up for a second, closes, then I get the following error:

X Error of failed request:  BadIDChoice (invalid resource ID chosen for this connection)
  Major opcode of failed request:  148 ()
  Minor opcode of failed request:  3
  Resource id in failed request:  0x200002
  Serial number of failed request:  26
  Current serial number in output stream:  18

The Opcodes

As per the Xorg opcode page (thanks Kenster):

• Major opcode: PRESENT extension (apparently called for things related to "frame representation timing" - screen refreshing, tear-free rendering, etc.)
• Minor opcode: X_PresentSelectInput request (apparently "selects a set of Present events to be delivered for the specified window on the X server specified by display" - source)

It sounds like it's just an initial request that's sent when setting up/running PRESENT-related things.

How do I fix this? Some help would be greatly appreciated.

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More System Info

Server

As per this well-known post for setting up X11 forwarding:

• /etc/ssh/sshd_config looks as follows:

  #AllowAgentForwarding yes   # unspecified
  X11Forwarding yes           # activated
  #X11DisplayOffset 10        # unspecified
  #X11UseLocalhost yes        # unspecified
  

• /etc/ssh/ssh_config looks as follows:

  #   FowardX11 yes           # unspecified
  #   ForwardX11Trusted yes   # unspecified
  

• xauth is installed

  $ xauth -V
  1.1
  

• The server's DISPLAY variable seems to be set correctly

  $ env | grep DISPLAY
  DISPLAY=localhost:10.0
  

• The XAUTHORITY variable seems empty

  $ env | grep XAUTHORITY
  $
  

PuTTY

• Obviously "Enable X11 forwarding" box is checked

• "X display location" is empty

  

X Server (VcXsrv)

Using XLaunch:

• "Display number" is -1 (to let vcxsrv automatically choose one)
• "Disable access control" box is unchecked

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What I've Tried

The following all yield the BadIDChoice error mentioned up top:

• (After reading David G.'s answer) Enabled ForwardX11Trusted in /etc/ssh/ssh_config, together with "Disable access control" in XLaunch
  • Tried once with X11UseLocalhost no in /etc/ssh/sshd_config
  • Tried once with #X11UseLocalhost yes (commented out)
• Changing VcXsrv "Display number" to 0
• Changing PuTTY "X display location" to localhost:0

Other Errors:

• Changing VcXsrv "Display number" to 1 or 10 --> yields (4 times for some reason):

  PuTTY X11 proxy: unable to connect to forwarded X server: Network error: Connection refused
  

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Answer 1

openssh, at least, has the concept of two different levels of X11 forwarding, the second via ForwardX11Trusted or the -Y option. The error you are getting appears to be an untrusted connection. The issue being, there really aren't invalid IDs, just IDs that you are not trusted to access. I find that many more complex applications don't work in the untrusted connection.

There is an "X11 SECURITY Extension" involved, and I've seen documentation on it in the past, but I'm not sure where.

In any case, it is the SSH client and local X server where the problem lives.