Black screen/error 10054/VPN
garry "at" trellisconsulting.ca
Tue Nov 15 23:56:01 2005
You hit the nail on the head. Its working, after reducing my MTU.
James Weatherall wrote:
> The problem is probably that your VPN has an MTU smaller than the underlying
> network, but that your servers are not detecting that correctly - this is a
> very common flaw in many VPN setups, and will affect any protocol that
> transfers non-trivial amounts of data, e.g. FTP, HTTP, etc.
> You will find that VNC can connect and will attempt to authenticate you, but
> that you'll then get a blank screen and an eventual disconnect error - this
> is because your server's TCP/IP stack is sending network data segments that
> are larger than the VPN can support, so it's simply dropping them. To the
> TCP/IP stacks at both ends, it appears that the connection has been lost, as
> a result. Because connecting & authenticating involve small amounts of
> data, they don't exhibit this problem.
> Wez @ RealVNC Ltd.
>>From: vnc-list-admin "at" realvnc.com
>>[mailto:vnc-list-admin "at" realvnc.com] On Behalf Of Garry Dunn
>>Sent: 15 November 2005 01:20
>>To: vnc-list "at" realvnc.com
>>Subject: Black screen/error 10054/VPN
>>I've been trying to get RealVNC (4.1.1) running through a VPN and I'm
>>having no luck. Could someone give me ideas as to what's
>>Here is the setup:
>>Computer A is in the main office. It sits behind a
>>Computer B is in a remote office. It sits behind a
>>Computer C is in a second remote office. It sits behind a
>>Computer D is in a test site. It sits behind a firewall
>>without a VPN
>>I've got a public IP address I can hit for Computer A, B and
>>C and I can
>>get control over any of those VNC terminals from Computer D.
>>goes for Computer A to Computers B or C (through the public
>>If I try from Computer A to Computer B or C through the VPN
>>private IP), I will be asked for the VNC password, which it
>>and bring up a black remote screen. I never get the remote
>>screen is the correct size, but black). After roughly 15
>>get the error code 10054 and the connection is lost. The remote user
>>tells me they can see the mouse moving on their screen. The
>>lists a 'timeout' as the reason for the connectionn being dropped.
>>It seems obvious the problem is related to the VPN (remember:
>>I can use
>>the public IP addresses without issues). But what is the
>>run a ping in the background while I'm trying to connect
>>through the VPN
>>and the computer will ping consistently (even after the error 10054).
>>The ping times are roughly 40ms to Computer B and 70ms to Computer C.
>>All the internet connections are DSL (1Mbit/s or greater--not
>>I've run through the archives and I think I've got everything covered
>>that is suggested there:
>>1) fast user switching is off
>>2) the rate limiting is on for mouse movements
>>I'm running Windows XP SP2 on Computer A and B. Computer C
>>XP SP1. Computer D is Windows 98. I've tried RealVNC 3.7.7, 4.0 and
>>4.1.1. They all do virtually the same thing. I can telnet to the
>>private IP address (port 5900) and get the RFB response.
>>I've been playing with the firewall configurations to make sure that
>>port 5900 is passed through the firewall and it is. Based on the VNC
>>authentication being granted, I'd say that is true. But why do I not
>>get screen updates and lose the connection 15 seconds later?
>>Any ideas would be greatly appreciated.
>>VNC-List mailing list
>>VNC-List "at" realvnc.com
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Garry Dunn, P.Eng