What on Earth is Session Zero?

John Aldrich JAldrich "at" covista.com
Tue Nov 1 21:34:00 2005


Stephen:
Since Outlook has lousy quoting, I'm going to copy/paste your questions here
and answer 'em again one-by-one.
> What's the difference between a double colon and a single colon, and why
does
> ip address:5900 work on the ME PC with a single colon? 
Single colon -- :
Double Colon -- ::
As for why "IP:5900" works, I'm going to guess that VNC is smart enough to
know that :5900 means the "default" session. You don't have to specify a
port or session in the viewer if you use port 5900.
> Is ip address:0 what is meant by "session zero"? 
Yes
> Is ip address:20 session 20? Is ip address::5920 session 20? 
Yes and no... They're both ways of specifying that you want to connect to
port 5920. On a *nix machine, that would be session 20, however, on a
Windows box, which only supports one active user session (due to operating
system limitations, NOT VNC) it's just a way of specifying a non-standard
port for the connection.

> Is ip address:5920 incorrect syntax? 
Yes. That is invalid.
As an aside, why are you using port 5920? Why can't you use 5900 or 5901? I
realize you have another machine listening on 5900, but you can specify a
different port on your router and have that forward to port 5900 on a
particular IP address on your lan. That is, say port 5901 (or IP:1)
externally would go to 192.168.x.y port 5900 and external port 5900(i.e.
IP:0) would go to 192.168.a.b port 5900. A lot of people do that and it
works great.

If you're still confused try reading http://faq.gotomyvnc.com. There's a lot
of good information there which you might find helpful. Also
http://www.portforward.com can help you figure out how to configure your
router's forwarding.

-----Original Message-----
From: Stephen [mailto:stephen "at" sptv.demon.co.uk]
Sent: Tuesday, November 01, 2005 4:14 PM
To: John Aldrich
Subject: Re: What on Earth is Session Zero?


----- Original Message -----
From: "John Aldrich" <JAldrich "at" covista.com>
To: "'Stephen'" <stephen "at" sptv.demon.co.uk>
Cc: <vnc-list "at" realvnc.com>
Sent: Tuesday, November 01, 2005 8:59 PM
Subject: RE: What on Earth is Session Zero?


> That's the problem... you either need to do DOUBLE-colon 5920 or just :20
> (SINGLE-Colon)
>
> Best to do the DOUBLE-colon and the port number if you're using something
> other than the default, in my personal opinion. Give that a shot and see
if
> it works.

I will try this next time I get a chance. What's the difference between a
double colon and a single colon, and why does
ip address:5900 work on the ME PC with a single colon? Is ip address:0 what
is meant by "session zero"? Is ip address:20 session 20? Is ip address::5920
session 20? Is ip address:5920 incorrect syntax?

> John
>
> -----Original Message-----
> From: Stephen [mailto:stephen "at" sptv.demon.co.uk]
> Sent: Tuesday, November 01, 2005 3:15 PM
> To: John Aldrich
> Cc: vnc-list "at" realvnc.com
> Subject: Re: What on Earth is Session Zero?
>
>
> ----- Original Message -----
> From: "John Aldrich" <JAldrich "at" covista.com>
> To: "'Stephen'" <stephen "at" sptv.demon.co.uk>; "Steven D. Clark"
> <sdclark "at" cnrgroup.com>
> Cc: <vnc-list "at" realvnc.com>
> Sent: Tuesday, November 01, 2005 7:48 PM
> Subject: RE: What on Earth is Session Zero?
>
>
> > Stephen:
> > How, EXACTLY are you trying to connect? Your connection dialog window
> should
> > have something like this: remotemachine:20 or (better)
remotemachine::5920
> > If you're just typing in "remotemachine" and hitting "connect" that
> explains
> > it. VNC is NOT listening on 5900 on the XP box and unless you specify
the
> > port number, you're going to get that error.
>
> This is what I type in to VNC Viewer
> ip address:5920
> At the other end both User Mode and Service Mode configuration windows are
> set for 5920 and http 5820.
>
> Previously, the ME PC at the other end was always off, User Mode and
Service
> Mode configuration windows on the XP PC were on their default settings
5900
> and http 5800, and I was typing this in to VNC Viewer
> ip address:5900
>
> The result has always been Error 10061, or 10065. The router at the remote
> end is wide open to all incoming connections, Windows Firewall is off,
> winvnc4.exe is listed as an exception in Windows Firewall anyway, and
there
> is no other firewall or security software installed. As far as I can tell
> Real VNC server is running, listening, and refusing all connections. Since
> there is no setting in the Real VNC server configuration which I can alter
> to change this, I concluded that Real VNC is not compatible with Windows
XP
> Home Edition.
>
> > -----Original Message-----
> > From: vnc-list-admin "at" realvnc.com [mailto:vnc-list-admin "at" realvnc.com]On
> > Behalf Of Stephen
> > Sent: Tuesday, November 01, 2005 2:22 PM
> > To: Steven D. Clark
> > Cc: vnc-list "at" realvnc.com
> > Subject: Re: What on Earth is Session Zero?
> >
> >
> > ----- Original Message -----
> > From: "Steven D. Clark" <sdclark "at" cnrgroup.com>
> > To: <vnc-list "at" realvnc.com>
> > Sent: Tuesday, November 01, 2005 3:53 PM
> > Subject: Re: What on Earth is Session Zero?
> >
> > > Does XP Home allow you to run "netstat -a" in a command window?
> > > You should see the following lines if VNC is listening:
> > >
> > >   TCP    <name-of-xp-box>:5800     <name-of-xp-box>:0        LISTENING
> > >   TCP    <name-of-xp-box>:5900     <name-of-xp-box>:0        LISTENING
> >
> > Yes it does. Below is my result from netstat -a on the XP PC.This was
> after
> > connecting it with "Add New Client" from the remote end, and starting up
> > Windows Media Encoder on Port 8080. The RealVNC ports are 5920 and 5820.
A
> > Windows ME computer (192.168.0.2 on the router also at the remote end)
> uses
> > Real VNC on 5900 and 5800 when it is on, and I CAN get into to that one
> with
> > RealVNC Viewer. The refusal to connect on the XP PC I need (192.168.0.3
on
> > the router at the remote end) does not change whether the ME PC is on or
> > off. The router is configured to allow everything inbound to both as
here:
> >
> > Inbound Services
> >  #  Enable  Service Name  Action  LAN Server IP address  WAN Users  Log
> >  1   Yes Any(ALL)  ALLOW always  192.168.0.2  Any  Always
> >  2   Yes Any(ALL)  ALLOW always  192.168.0.3  Any  Always
> >  Default  Yes  Any  BLOCK always  Any  Any  Never
> >
> > netstat -a
> > Active Connections
> >
> >   Proto  Local Address           Foreign Address        State
> >   TCP    YOUR-91C305C62F:epmap   YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:microsoft-ds   YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:2869    YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:5820    YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:5920    YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:8080    YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:1028    YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:netbios-ssn   YOUR-91C305C62F:0      LISTENING
> >   TCP    YOUR-91C305C62F:1049    sptv.demon.co.uk:5500  ESTABLISHED
> >   TCP    YOUR-91C305C62F:8080    sptv.demon.co.uk:1159  ESTABLISHED
> >   TCP    YOUR-91C305C62F:8080    sptv.demon.co.uk:1174  FIN_WAIT_2
> >   UDP    YOUR-91C305C62F:microsoft-ds   *:*
> >   UDP    YOUR-91C305C62F:isakmp   *:*
> >   UDP    YOUR-91C305C62F:1069    *:*
> >   UDP    YOUR-91C305C62F:4500    *:*
> >   UDP    YOUR-91C305C62F:ntp     *:*
> >   UDP    YOUR-91C305C62F:1035    *:*
> >   UDP    YOUR-91C305C62F:1900    *:*
> >   UDP    YOUR-91C305C62F:ntp     *:*
> >   UDP    YOUR-91C305C62F:netbios-ns   *:*
> >   UDP    YOUR-91C305C62F:netbios-dgm   *:*
> >   UDP    YOUR-91C305C62F:1900    *:*
> >
> >
> > > ----- Original Message -----
> > > From: "John Aldrich" <JAldrich "at" covista.com>
> > > To: "'Stephen'" <stephen "at" sptv.demon.co.uk>; <vnc-list "at" realvnc.com>
> > > Sent: Tuesday, November 01, 2005 8:16 AM
> > > Subject: RE: What on Earth is Session Zero?
> > >
> > >
> > > > Stephen:
> > > > Are you running any antivirus software, such as "Norton Internet
> > > Security"?
> > > > There is sufficient anecdotal evidence that some antivirus products
> > > actively
> > > > block VNC because they perceive it as "malware" due to the fact that
> it
> > > > could be misused.
> > > >
> > > > The first thing I would try is to connect from your Windows ME box
to
> > your
> > > > XP box and see if that works. If it doesn't, try the following:
> > > > Start ->Run ->Telnet <ip.of.xp.box> 5900
> > > > and see if you get an "RFB" prompt. If you don't, then your machine
is
> > not
> > > > accepting connections. My XP Pro box appears to be having the same
> > > problem,
> > > > but I'm not blaming it on VNC, because it works fine on other XP
> boxes.
> > > > _______________________________________________
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