(I am not looking for answers such as "Stop using VNC as it is insecure", nor do I need answers recommending different VNC implementations, as I'm specifically wanting to get TigerVNC to function properly).
I need to display and control a Ubuntu 18.10 desktop from an Ubuntu 18.10 laptop, using TigerVNC. Both machines have been upgraded to 18.10 recently.
I have enabled desktop sharing on the desktop via the instructions in https://askubuntu.com/a/1088328 with with this exception: When I have not executed the following command:
gsettings set org.gnome.Vino require-encryption false
it does not work (see below). But when I do use that gsettings
command on the desktop, then I to get a prompt for the vnc password,
and upon typing it in, I'm able to control the desktop. So
ultimately, I know that must be the fix, but I specifically need to
know why that would be required (see remmina usage below). None of my
web searches have provided an answer of why.
On the desktop machine, the Sharing settings are:
Note: I can successfully use the remmina tool, using the VNC setting,
to connect to the desktop machine and display it, without using the
above gsettings setting on the desktop machine. But, when I use the
TigerVNC type of vncviewer using this command:
vncviewer thedesk.local:0
(where thedesk.local is the Ubuntu desktop machine), I get a popup with:
No matching security types
And the output into the shell shows:
$ vncviewer thedesk.local:0
TigerVNC Viewer 64-bit v1.9.0
Built on: 2018-07-29 13:31
Copyright (C) 1999-2018 TigerVNC Team and many others (see README.rst)
See http://www.tigervnc.org for information on TigerVNC.
Sun May 26 07:10:29 2019
DecodeManager: Detected 8 CPU core(s)
DecodeManager: Creating 4 decoder thread(s)
Sun May 26 07:10:30 2019
CConn: connected to host thedesk.local port 5900
Sun May 26 07:10:31 2019
CConnection: Server supports RFB protocol version 3.7
CConnection: Using RFB protocol version 3.7
CConnection: No matching security types
CConn: No matching security types
On both the Ubuntu 18.10 laptop and the desktop machines, I have these
installed versions of vnc-like packages, apt remove-ing all other
flavors of "vnc" clients/servers to avoid confusion with the
Linux "alternatives" mechanism:
$ dpkg --list *vnc* | grep '^i'
ii libvncclient1:amd64 0.9.11+dfsg-1.1ubuntu0.1 amd64 API to write one's own VNC server - client library
ii remmina-plugin-vnc:amd64 1.2.31.4+dfsg-1ubuntu1 amd64 VNC plugin for Remmina
ii tigervnc-common 1.9.0+dfsg-1 amd64 Virtual network computing; Common software needed by servers
ii tigervnc-standalone-server 1.9.0+dfsg-1 amd64 Standalone virtual network computing server
ii tigervnc-viewer 1.9.0+dfsg-1 amd64 Virtual network computing client for X
$ vncviewer --version |& head -5
TigerVNC Viewer 64-bit v1.9.0
Built on: 2018-07-29 13:31
Copyright (C) 1999-2018 TigerVNC Team and many others (see README.rst)
See http://www.tigervnc.org for information on TigerVNC.
$
remmina --version pops up with a dialog that reads:
1.2.31.4 (git n/a)
The reason remmina is involved is just to show that some client is able to talk to the Ubuntu desktop, just not TigerVNC. I've tried connecting to thedesk.local from a Raspberry Pi 3 B+ running Raspbian and got a different error, but still seemingly involving a similar incompatibility with security protocols between VNC implementations. The error is:
So, what is remmina providing to the X server (or VNC server?) running on display :0 on thedesk.local, that the TigerVNC viewer client (or that RealVNC client running under Raspbian) is not providing?
My web searches turn up results such as
https://ubuntuforums.org/showthread.php?t=2384046 which give "Why
don't you do 'X' instead?" type of responses, which is a fair
observation. But I specifically want to find out why I would have to
use the gsettings change just to get TigerVNC viewer to popup the
prompt, while remmina does not require it. (When I need to have
security, I know how to tunnel traffic over SSH already.)
