On Mon, Aug 06, 2007 at 10:48:20AM -0400, Boyd Campbell wrote: > Please recall from my message that it works fine from some locations and is > consistent across machines at those locations. IE: All machines at certain > locations work and all machines at other locations get the black screen. I > fail to see how the server is the issue, but I'm still open to your > suggestions and will review the link.
That behaviour is exactly the expected behaviour when the server tries to do a Path MTU Discovery but fails (in some cases.) On the working networks the MTU used by the server fits on all path components (the Path MTU Discovery is never triggered or works as expected.) On the non-functional networks the MTU used by the server triggers an ICMP request to fragment the data, but that request is dropped/filtered by some network equipment on its way back to the server. But again, I'm just guessing. Cheers, Peter > Anyone else with thoughts? I'd very much like to hear from the VNC > community. Thank you. > > -----Original Message----- > From: Peter Rosin [mailto:[EMAIL PROTECTED] > Sent: Monday, August 06, 2007 5:11 AM > To: Boyd Campbell > Cc: vnc-list@realvnc.com > Subject: Re: Inconsistent Black Screen issues... > > On Mon, Aug 06, 2007 at 12:03:02AM -0400, Boyd Campbell wrote: > > Good evening all, > > > > I'm using VNC to connect to a specific server on a remote LAN from > > many different clients at many different locations. However, using the > > same machine on one network vs. another, I'm either able to get into > > the server in question fine or I get a black screen with no visual. > > The mouse is moving on the server and a hard connection is made, but > > the client only gets a black screen. IE: Using a single laptop, I can > > get connected instantly from one LAN with no issues, yet from another > > LAN, black screen. I'm also able to connect from different machines on > > the LAN's that work. All machines in question thus far have been XP > > Pro, SP2, RDP & User Switching off (neither of which really matter > > anyways, since I am indeed able to connect using the same machine(s) > > from one network but not another). Also, the server in question is > > behind a VPN router with port forwarding to 5900 on (hence our being > > able to connect to begin with). I've even gone to lengths of messing > > with the MTU & RWIN settings and used the TCP/IP Optimizer off from > SpeedGuide.net...all to no avail. > > > > I've searched many lists and Google high and low for answers to > > this issue. As I'm sure you well know, this issue has been an issue > > for many years with VNC, but I haven't been able to find any > > definitive answers by the VNC folks or others. Most of the answers > > I've found were merely suggestions that appeared to be just shots in > > the dark (simply my perception based on verbiage). In my humble > > opinion, if this is to be a viable product, then this issue needs to > > be addressed once and for all, being put under the VNC FAQ's since it > > is most certainly a FAQ on every list I've found, regardless of the > > domain I've found the issue listed on. But I've found everything from > > simple answers to uber-geek answers, none of which have helped and none of > which I've been able to find on the VNC site. > > > > I very humbly state, if RealVNC, Ltd. expects me, my company and > > my clients to drop cash for the Enterprise versions of this software, > > then someone needs to show me that the tool will work from anywhere > > around the world with an internet connection if I go with it. I'm > > using the free one now as a POC. But thus far, things have been > > problematic at best, and I've not been able to find any viable > > solutions from the VNC technical community at large. > > > > I would very much appreciate any help you all can lend. > > You say that you have played with MTU, does that include playing with the > server? Did you try to disable its Path MTU Discovery which is my bet at > what is wrong here (since largish amounts of data is not getting from the > server to the client). Or maybe I should wager that the server (or some > firewall) blocks the relevant ICMP messages needed for Path MTU Discovery... > > See http://www.netheaven.com/pmtu.html for some background on my wild guess. > > Cheers, > Peter _______________________________________________ VNC-List mailing list VNC-List@realvnc.com To remove yourself from the list visit: http://www.realvnc.com/mailman/listinfo/vnc-list
