Hello,
unvc works well with encryption.
uvnc sx works well without encryption.
uvnc sx with encryption has problems:
helpdesk.txt
-plugin -connect 192.168.2.110:54320 -noregistry
viewer was started with:
...\vncviewer.exe -listen 54320 -dsmplugin MSRC4Plugin.dsm
After double click in uvnc-sc on viewer-pc pops up "VNC Authentication" (why?, i think here is the problem!).
When i click on "Log On" or "Cancel", popup is closed, nothing else happens (no viewer-window!).
On server-pc connection is active, sc-server is listening, and with contextmenu on systray-icon connection can be closed.
After closing connection on server-pc on viewer-pc pops up "VncViewerMessage Box" with message:
Connection failed: Error reading Protocol Version ...
I think that a viewer-parameter is wrong.
Thanks for every kind of help!
Best wishes
walter01
After more 2 000 000 (two million) views on forum for 1.5.0.x development versions... and 1.6.1.0, 1.6.3.0-dev versions
A new stable version, UltraVNC 1.6.4.0 and UltraVNC SC 1.6.4.0 have been released: https://forum.uvnc.com/viewtopic.php?t=38095
Feedback is always welcome
2025-12-05: Celebrating the 23th anniversary of the UltraVNC (26th anniversary since the laying of the foundation stone): https://forum.uvnc.com/viewtopic.php?t=38130
2025-12-03: Could you please complete our poll/survey? Renaming UltraVNC files and service to be more clear: https://forum.uvnc.com/viewtopic.php?t=38128
There was a problem to vote, it is solved now! Thanks in advance!
2025-12-02: We need help: English Wikipedia UltraVNC page has been requested to deletion: https://forum.uvnc.com/viewtopic.php?t=38127
Any help is welcome to improve the UltraVNC page and/or to comment on the Wikipedia Talk page
2025-05-06: Forum password change request: https://forum.uvnc.com/viewtopic.php?t=38078
2023-09-21: Important: Please update to latest version before to create a reply, a topic or an issue: https://forum.uvnc.com/viewtopic.php?t=37864
Development: UltraVNC development is always here... Any help is welcome
Feedback is welcome
Join us on social networks and share our announcements:
- Website: https://uvnc.com/
- GitHub: https://github.com/ultravnc
- Mastodon: https://mastodon.social/@ultravnc
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- X/Twitter: https://x.com/ultravnc1
- Reddit community: https://www.reddit.com/r/ultravnc
- OpenHub: https://openhub.net/p/ultravnc
A new stable version, UltraVNC 1.6.4.0 and UltraVNC SC 1.6.4.0 have been released: https://forum.uvnc.com/viewtopic.php?t=38095
Feedback is always welcome
2025-12-05: Celebrating the 23th anniversary of the UltraVNC (26th anniversary since the laying of the foundation stone): https://forum.uvnc.com/viewtopic.php?t=38130
2025-12-03: Could you please complete our poll/survey? Renaming UltraVNC files and service to be more clear: https://forum.uvnc.com/viewtopic.php?t=38128
There was a problem to vote, it is solved now! Thanks in advance!
2025-12-02: We need help: English Wikipedia UltraVNC page has been requested to deletion: https://forum.uvnc.com/viewtopic.php?t=38127
Any help is welcome to improve the UltraVNC page and/or to comment on the Wikipedia Talk page
2025-05-06: Forum password change request: https://forum.uvnc.com/viewtopic.php?t=38078
2023-09-21: Important: Please update to latest version before to create a reply, a topic or an issue: https://forum.uvnc.com/viewtopic.php?t=37864
Development: UltraVNC development is always here... Any help is welcome
Feedback is welcome
Join us on social networks and share our announcements:
- Website: https://uvnc.com/
- GitHub: https://github.com/ultravnc
- Mastodon: https://mastodon.social/@ultravnc
- Bluesky/AT Protocol: https://bsky.app/profile/ultravnc.bsky.social
- 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
problems with encryption
- Rudi De Vos
- Admin & Developer

- Posts: 6978
- Joined: 2004-04-23 10:21
- Contact:
Re: problems with encryption
did you added the rc4.key file.
But server and viewer need the same key file.
Via the plugin options, you need to generate a key, and call it rc4.key.
uvnc has a password, uvnc sc doesn't have a password.
If no key file exist, the password is used, this doesn't work for sc.
+The rc4.key is actual a dual protection
-used for encryption
-only viewer with the correct key file can connect.
But server and viewer need the same key file.
Via the plugin options, you need to generate a key, and call it rc4.key.
uvnc has a password, uvnc sc doesn't have a password.
If no key file exist, the password is used, this doesn't work for sc.
+The rc4.key is actual a dual protection
-used for encryption
-only viewer with the correct key file can connect.
UltraVNC links (join us on social networks):
- Website: https://uvnc.com/
- Forum: https://forum.uvnc.com/
- GitHub sourcecode: https://github.com/ultravnc/UltraVNC
- Mastodon: https://mastodon.social/@ultravnc
- Bluesky/AT Protocol: https://bsky.app/profile/ultravnc.bsky.social
- 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
- uvnc2me: https://uvnc2me.com/
- Website: https://uvnc.com/
- Forum: https://forum.uvnc.com/
- GitHub sourcecode: https://github.com/ultravnc/UltraVNC
- Mastodon: https://mastodon.social/@ultravnc
- Bluesky/AT Protocol: https://bsky.app/profile/ultravnc.bsky.social
- 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
- uvnc2me: https://uvnc2me.com/
Re: problems with encryption
wrong, single colon for non standard port
-plugin -connect 192.168.2.110:54320 -noregistry
correct, with port outside of standard port need double colons
-plugin -connect 192.168.2.110::54320 -noregistry
-plugin -connect 192.168.2.110:54320 -noregistry
correct, with port outside of standard port need double colons
-plugin -connect 192.168.2.110::54320 -noregistry
UltraVNC 1.0.9.6.1 (built 20110518)
Windows OS: XP Home + Vista Business + 7 Home
Only experienced user, [u]not[/u] developer
Windows OS: XP Home + Vista Business + 7 Home
Only experienced user, [u]not[/u] developer
Re: problems with encryption
thanks for your help.
I copied again rc4.key in the uvnc-program-folder of both pc's,
i inserted double colons in the file helpdesk.txt,
i created a new exe-file with copy of rc4.key and changed helpdesk.txt,
but i get no connection with encryption, without encryption all is ok.
Do you have another idea?
Best wishes,
Reinhardt (walter01)
I copied again rc4.key in the uvnc-program-folder of both pc's,
i inserted double colons in the file helpdesk.txt,
i created a new exe-file with copy of rc4.key and changed helpdesk.txt,
but i get no connection with encryption, without encryption all is ok.
Do you have another idea?
Best wishes,
Reinhardt (walter01)
Re: problems with encryption
Which version of UltraVNC you are using in your pc?
Be aware the different versions of MSRC4Plugin.dsm are not compatible.
In the previous UVNC package, the bundled MSRC4Plugin is 1.2.2.0 (the latest version using 1.2.4.0)
The SingleClick Online creator is using MSRC4Plugin.dsm 1.2.4.0
Be aware the different versions of MSRC4Plugin.dsm are not compatible.
In the previous UVNC package, the bundled MSRC4Plugin is 1.2.2.0 (the latest version using 1.2.4.0)
The SingleClick Online creator is using MSRC4Plugin.dsm 1.2.4.0

