Cannot connect from Mac client to Linux server, “Protocol Error”

[stargrazer82301]

Dear NoMachine

I am having a recurring issue where I am unable to connect to a NoMachine server (on Linux RHEL 9 system) from a Mac client.

It goes through multiple cycles of “attempting to reconnect: protocol error”, before finishing with “The connection with the server was lost. Error is 100: protocol error”.

Oddly, other people on the network trying to connect to the same Linux server, also from Mac, are able to do so.

Our admins have tried running:
sudo systemctl stop gdm
sudo /etc/NX/nxserver –restart

On the server, but to no avail.

I have updated to the latest version of the NoMachine Mac client.

I have attached the logs provided by the crash.

Help very much appreciated!

Attachments:

1. plesiosaurus-logs-2025-08-19-21.29.45.zip

[Britgirl]

Hi, we would need to see the NoMachine server logs from the host you are connecting to and the from the Player device you are connecting from. Are you using the latest version on both sides, 9.1.24? You can extract them using the instructions here: https://kb.nomachine.com/DT08U00298#1. Attach here or send them to forum[at]nomachine[dot]com. Please use the title of this topic as the subject of your email. Thanks!

[stargrazer82301]

Hi; many thanks. I just emailed the logs to that address.

The problem has come and gone several times. Occurred about 1.5 months ago, lasted for ~1.5 weeks, then went away again. It has come back again for the past week. We have updated the server and client a couple of times during this period. The client is definitely on the 9.1.24; the server is either on that, or the previous version. However the problem seems to persist across versions.

[Britgirl]

Hi, thanks for the logs. The agent logs were missing, unfortunately. Can you send us the .nx directory from the user’s home on the Linux server side? Just zip up and send via email. Thanks!

[stargrazer82301]

Ah, apologies for the oversight. I just emailed them. Thanks again.

[Britgirl]

Not received anything so far.

[stargrazer82301]

Ah, the email bounced due to attached zip breaching size limit? (It’s 5MB). I just sent another email, with a download link,

[Britgirl]

Logs point to a problem with Gnome, rather than NoMachine. Logs are showing this:

2919520 2919520 2025-08-25 11:02:12 205.757 NXNODE WARNING! Process '/bin/bash --norc -c exec -a - /bin/bash -c '/bin/dbus-launch --exit-with-session gnome-session --session=gnome'' with pid '2919612/2919612' finished with exit code 1 after 1,369 seconds.

NoMachine correctly tries to start a virtual display because it detects that your Linux is headless. But Gnome fails to start. Looking in the journalctl file would identify what is happening with Gnome.

journalctl -b -0 > journal.txt

[stargrazer82301]

Interesting, thanks.

journalctl shows the following error comes up whenever I try to connect into NoMachine:

wireplumber[545931]: GetManagedObjects() failed: org.freedesktop.DBus.Error.NameHasNoOwner

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