Tiger VNC server using dynamic port assignment via system unit file socket?

[Jibun no Kage]

I have a working Xvnc configuration, I created the socket file, the service file, etc.  Using GNOME and gdm3 without wayland, since still need x11, and of course XDMCP enabled.  Everything is working fine.

However, when I switch from Xvnc binary to the tigervncserver binary I get, from tigervnc viewer, I get "An unexpected error occurred while communicating with the server: Reading version failed, not an RFB server?"

The only change in the configuration as outlined above is the following...

# This works...

ExecStart=/usr/bin/Xvnc -inetd -query localhost -once securitytypes=None

# This does not work...
ExecStart=/usr/bin/tigervncserver -inetd -query localhost -once securitytypes=None --I-KNOW-THIS-IS-INSECURE

The logs show nothing of note on the tigervncserver side, and the error message implies client side?  No?  Is this a bug of some kind in tigervnc viewer?

Below is the socket file and service files for reference...

```

/etc/systemd/system/tigervncserver.socket
[Unit]
Description=Tiger VNC Server Socket

[Socket]
ListenStream=5900
Accept=yes

[Install]
WantedBy=sockets.target

```

Below works...

```

nano /etc/systemd/system/tigervncserver@.service

// Add/Change...
[Unit]
Description=Tiger VNC Server (XDMCP) Session
After=network.target

[Service]
ExecStart=/usr/bin/Xvnc -inetd -query localhost -once securitytypes=None
StandardInput=socket

[Install]
WantedBy=multi-user.target

```

Below does not work...

```

nano /etc/systemd/system/tigervncserver@.service

// Add/Change...
[Unit]
Description=Tiger VNC Server (XDMCP) Session
After=network.target

[Service]
ExecStart=/usr/bin/tigervncserver -inetd -query localhost -once securitytypes=None --I-KNOW-THIS-IS-INSECURE
StandardInput=socket

[Install]
WantedBy=multi-user.target

```

Any assistance greatly appreciated.  Thanks.

[Pierre Ossman]

On 25/05/2026 03:59, Jibun no Kage wrote:
>
> # This does not work...
> ExecStart=/usr/bin/tigervncserver -inetd -query localhost -once
> securitytypes=None --I-KNOW-THIS-IS-INSECURE
>

That command is not meant to be used for XDMCP and will just ignore
those flags. Calling Xvnc directly is the correct way to use XDMCP.

What are you trying to achieve by switching out the command here?

Regards,
--
Pierre Ossman Software Development
Cendio AB http://cendio.com
Teknikringen 8 http://twitter.com/ThinLinc
583 30 Linköping http://facebook.com/ThinLinc
Phone: +46-13-214600

A: Because it messes up the order in which people normally read text.
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