[Box-Admins] Re: best practice RFB for Squeak-based server

Levente Uzonyi leves at caesar.elte.hu
Sun Aug 28 10:44:26 UTC 2016


Hi Chris,

X forwarding and RFB/VNC are two entirely different things. Let's not mix 
X forwarding here.

Squeak's RFB server and external VNC servers are also different things. 
They use the same protocol, but they work differently.

If you use Squeak's RFB server, which is the preferred way IMO, then you 
don't have to use any external software. It's more responsive than an 
external RFB server, because it knows the rectangles which have changed, 
and it can use the same framebuffer as the image uses. It's only drawback 
is that Cmd+. will not always work, as it may interrupt one of the RFB 
server's processes.

To set it up, just load the RFB package (I suggest you use this one for 
5.1: http://leves.web.elte.hu/squeak/RFB-ul.14.mcz ), disable "allow 
remote connections", then start it on an unused port. The other default 
settings should be fine.

How to choose the port?
I prefer to keep RFB ports and Web ports in sync on a server. So if your 
web ports start from 8080 and RFB ports start from 5900 and let's say 8083 
is free, then the RFB port 5903 should be used. When you start RFB, you 
have to pass the display number, which is RFB port minus 5900. So if you 
want the RFB server to listen on 5903, then you have to start it on 
display 3.

How to connect to the RFB server?
You have to forward the port via ssh from your local machine. For example 
if the RFB port is 5903, then when you connect to the server, you add the 
parameter

 	-L 5903:127.0.0.1:5903

to the ssh command. Then you open your VNC client on your machine and 
connect to 127.0.0.1:5903. If your program uses display numbers you'll use 
display 3. Note that you can manage the tunnels of an existing 
connection[1].

Some VNC clients don't seem to work well with Squeak's RFB server. You 
can make these work, by setting the encoding to ZRLE and the color space 
to max (24-bit).

Levente

[1] https://en.wikibooks.org/wiki/OpenSSH/Cookbook/Tunnels#Adding_or_Removing_Tunnels_within_an_Established_Connection

On Sat, 27 Aug 2016, Chris Muller wrote:

> Hi Levente and all, I unfortunately have only ever hobbled along with
> "whatever I can get to work" when it comes to VNC.  It seems like it
> always only barely works -- for example, using Squeak's RFB on on my
> local laptop works fine viewing with Ubuntu's Remmina, but not the
> commercial "vncviewer".
>
> On box4, I'm not sure what our viewer is, Xtightvnc?  Or, is that the
> Xtight server because I know I've used a "xtightvncviewer" before...
>
> My strategy was to start RFB server in Squeak to accept local
> connections only.  Then I was going to use ssh -X when I logged in to
> box4 from terminal, and then, xtightvncviewer :6900.  Is this a flawed
> strategy?  Your expertise could save me a lot of time from research
> and trial and error by sharing your VNC best-practices with me.  :)
>
> When I tried Xtightvnc :6900, it said:
>
> =========
> _XSERVTransSocketINETCreateListener: ...SocketCreateListener() failed
> _XSERVTransMakeAllCOTSServerListeners: server already running
>
> Fatal server error:
> Cannot establish any listening sockets - Make sure an X server isn't
> already running
> =========
>
> So yeah, Xtightvnc looks like a server, not a viewer, but I didn't
> want to install xtightvncviewer without asking the box-admins team
> leader first..
>
> Best.
>


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