VNC server with UDP connection. Has anyone done it?

[Dieselboy]

I have configured a RHEL 6.7 server and installed TigerVNC. In the Red Hat guide it states an option for the display "-nolisten TCP". I have done this but my VNC connections still use TCP. There are no UDP packets at all. I went back in to the config on the server and set the screen resolution there and restarted the vnc server. The screen now has the resolution I had set but still using TCP for the data.

Code Select Expand


VNCSERVERARGS[2]="-geometry 1024x768 -nolisten tcp"

Has anyone used VNC with UDP? I done some Googling around and it doesn't look like it's common. I noticed that Windows RDP uses UDP now.

I don't have a preference which VNC server I use but TigerVNC was a piece of cake to set up. Took me about 5 minutes and it's the first time I've been able to get VNC server running exactly how I needed it to. But, UDP isn't working.

If I did have UDP working, how would the connection flow work? Because my VNC client would still set up the TCP session first I think. But then it should establish a UDP connection as well and send the screen image over UDP.
- OR do I need to do something fancy with my VNC client?

[deanwebb]

I'm security, so as soon as I saw VNC, I thought, "SHUT THAT THING DOWN. NOW." As soon as I saw "VNC with UDP", I wanted to start applying to work somewhere else.

You don't plan on having this open to the Internet, do you?

[Dieselboy]

Hahahaha no way! Why did you say that?  Well, it has internet access but there's no inbound access from the internet. If they need to they can anyconnect VPN.

But VNC with UDP - surely it's the best thing in the world other than a Classic Brown Derby from Wimpy (warmed doughnut, with ice cream on top, choc sauce and a sprinkle of peanuts).

When I have 320ms RTT latency between end user and server, I think UDP will help a bit. Because everything you do in the gui session requires TCP ack. So I would expect it to be twice as fast with udp.

Without VNC how else do you gui into a RHEL desktop?

I'm actually really pleased with my work here. I built a RHEL system, added it to a Windows domain, gave a specific user "admin" access, done all the updates and added the virtualisation tools. And gave a specific user a VNC session to their own desktop. 

[Reggle]

Without VNC how else do you gui into a RHEL desktop?

X-Window forwarding over SSH.
Ironically, I got that to work before VNC/RDP here.

[Dieselboy]

Yes that's good but the access is internal only and protected through an untrusted network using IPSEC with UDP transport.

The problem I have is that the VNC session is TCP for transport, likewise SSH is TCP. I would like to have a VNC "stream" to reduce screen refresh-rate latency and I think UDP would go a long way beyond the current setup in terms of responsiveness. At least if I can try it out to see if there's an improvement.

I've raised a Red Hat support case as their documentation which I followed is not working for our set up. I can't see that I've missed anything so at least if I have, I'm hoping their support can fill the knowledge-gap.

When I was googling for answers last week I came across someone who managed to redirect the VNC session through a loopback, which then routed into UDP for transport. But I wasn't sure what needed to be done on the client end to use that functionality.

[Dieselboy]

I've set up a test using "nomachine" which I hate, but only to test because it uses UDP for transport. I verified this with Wiresharkingtons.

I gave the details to the developer using the VM. I said "pay attention to the instructions given when you connect, because it explains how to configure the settings".
The next thing he says to me after he connected was "where do I access the settings"


He then sends me a screenshot comparison of VNC to Nomachine. Nomachine has a lower res (it's default is automatic so it lowers the res based on the connection, to keep response good). He says look at the difference. I said "Yes, it looks like VNC is configured for "slow" experience."


I said to him to let me have his feedback, I anticipate nomachine being a little bit quicker as it's using UDP for the screen updates.

He says "VNC is better, both are too slow."


So again I'm asking "too slow for what?!"
... The chat goes silent again.

[deanwebb]

I see that he has a bright future as a developer.

[dlots]

If only it was on fire... then he might be able to claim correctly that it was the fire-wall for once.