Garry, 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. Regards, Wez @ RealVNC Ltd. > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Garry Dunn > Sent: 15 November 2005 01:20 > To: vnc-list@realvnc.com > Subject: Black screen/error 10054/VPN > > To all, > > 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 > going wrong? > Here is the setup: > > Computer A is in the main office. It sits behind a > firewall/VPN device. > Computer B is in a remote office. It sits behind a > firewall/VPN device. > Computer C is in a second remote office. It sits behind a > firewall/VPN > device. > Computer D is in a test site. It sits behind a firewall > without a VPN > connection. > > 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. > The same > goes for Computer A to Computers B or C (through the public > IP address). > > If I try from Computer A to Computer B or C through the VPN > (using the > private IP), I will be asked for the VNC password, which it > will accept > and bring up a black remote screen. I never get the remote > desktop (the > screen is the correct size, but black). After roughly 15 > seconds I'll > 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 > remote end > 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 > problem? I've > 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 > dial-up). > > 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 > is Windows > 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. > > Thanks, > > Garry > _______________________________________________ > VNC-List mailing list > VNC-List@realvnc.com > To remove yourself from the list visit: > http://www.realvnc.com/mailman/listinfo/vnc-list _______________________________________________ VNC-List mailing list VNC-List@realvnc.com To remove yourself from the list visit: http://www.realvnc.com/mailman/listinfo/vnc-list
