Update: UltraVNC 1.4.3.6 and UltraVNC SC 1.4.3.6: https://forum.uvnc.com/viewtopic.php?t=37885
Important: Please update to latest version before to create a reply, a topic or an issue: https://forum.uvnc.com/viewtopic.php?t=37864

Join us on social networks and share our announcements:
- Website: https://uvnc.com/
- GitHub: https://github.com/ultravnc
- Mastodon: https://mastodon.social/@ultravnc
- Facebook: https://www.facebook.com/ultravnc1
- X/Twitter: https://x.com/ultravnc1
- Reddit community: https://www.reddit.com/r/ultravnc
- OpenHub: https://openhub.net/p/ultravnc

Connection failed

Single Click discussions / bugs
Post Reply
stevezemlicka
Posts: 5
Joined: 2007-11-11 01:04

Connection failed

Post by stevezemlicka »

We have VNC SC setup with a menu for 6 different options. Each option goes to a different port with is redirected to the standard port and and appropriate internal IP address. Every option is unsecured.

This morning we started getting the following in mass

VncViewer Message Box
Connection failed - Invalid protocol !

Possible causes:

-You've forgotten to select a DSMPlugin and the Server uses a DSMPlugin


We also get the same message except after "Connection failed - " it reads "Error reading Protocol Version"


I just updated to viewer version 1.0.5.6
YY
200
200
Posts: 996
Joined: 2006-11-13 15:11

Re: Connection failed

Post by YY »

At the viewer pc, right click EYE Icon at Systray, select "New connection",

See if the "Use DSMPlugin" is checked.
stevezemlicka
Posts: 5
Joined: 2007-11-11 01:04

Re: Connection failed

Post by stevezemlicka »

No, it is not. Should it be?

We don't have any problem when we tell someone to connect to us. Connections work just fine, but when we are doing other work, these start popping up. I am relatively certain it is not a legitimate person trying to connect to us.
YY
200
200
Posts: 996
Joined: 2006-11-13 15:11

Re: Connection failed

Post by YY »

stevezemlicka wrote:No, it is not. Should it be?
If the box is not checked, then it is fine.

Because your SC.exe not using any secured setting (dsmplugin), I believe you were starting the viewer in listening mode w/o dsmplugin, but in some particular situation, the viewer will be running with DSMplugin "ON" automatically. In such case, the viewer may return your said error message.

stevezemlicka wrote: I am relatively certain it is not a legitimate person trying to connect to us.
If those connection came from non-legitimate person, then it is not a problem of UVNC/SC, just an unauthorised usage of your application, or someone using a port scanner to scan your network.
We can't help. :|
Last edited by YY on 2009-05-23 03:57, edited 1 time in total.
stevezemlicka
Posts: 5
Joined: 2007-11-11 01:04

Re: Connection failed

Post by stevezemlicka »

are there any known security implications by leaving several computers with the viewer listening over the port?
Post Reply