Hello!
I'm using UltraVNC a long time on many machines by using the commandline option "-connect".
This seems not working in Version 1.2.1.7 (on client side) - there's no connect and no error message.
However, when I use "add new client" from the taskbar icon it works. Also Version 1.2.1.6 works well.
This had happened now on 3 different computers (Win 10 Fall creator (1709) - 64Bit ).
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
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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:
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- GitHub: https://github.com/ultravnc
- Mastodon: https://mastodon.social/@ultravnc
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connecting via commandline in 1.2.1.7
- Rudi De Vos
- Admin & Developer

- Posts: 6978
- Joined: 2004-04-23 10:21
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Re: connecting via commandline in 1.2.1.7
vncviewer -connect localhost
seems to work
testen on build 10.0.16299
tested viewer 1.2.2.0
1217 x64 win8>
1217 x64 xp
Are you using plugins ?
Try without firewall, it could be blocking the viewer..
seems to work
testen on build 10.0.16299
tested viewer 1.2.2.0
1217 x64 win8>
1217 x64 xp
Are you using plugins ?
Try without firewall, it could be blocking the viewer..
UltraVNC links (join us on social networks):
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Re: connecting via commandline in 1.2.1.7
Thanks for the reply.
The problem takes place when using the vnc listening viewer - when the client wants to connect via
winvnc -connect <host>
I've tested it on differnet PC's with different firewalls and Antivirus Software (and disabling them). Even on a completely fresh installed system.
The problem takes place when using the vnc listening viewer - when the client wants to connect via
winvnc -connect <host>
I've tested it on differnet PC's with different firewalls and Antivirus Software (and disabling them). Even on a completely fresh installed system.
- Rudi De Vos
- Admin & Developer

- Posts: 6978
- Joined: 2004-04-23 10:21
- Contact:
Re: connecting via commandline in 1.2.1.7
Could it be this one
winvnc -connect <host>
Inject in running winvnc
winvnc -connect <host> -run
start a new winvnc and make connection to
winvnc -connect <host>
Inject in running winvnc
winvnc -connect <host> -run
start a new winvnc and make connection to
UltraVNC links (join us on social networks):
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- Reddit community: https://www.reddit.com/r/ultravnc
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- 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
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- uvnc2me: https://uvnc2me.com/