# TigerVNC mirrors my entire PC screen instead of showing the virtual HMI

**URL:** <https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998>\
**Category:** HMI & Visualization\
**Tags:** vnc\
**Created:** [November 12, 2025, 12:59pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998 "2025-11-12T12:59:17Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Hamsin](https://avatars.discourse-cdn.com/v4/letter/h/FF8800/32.png) [@Hamsin](https://community.br-automation.com/u/Hamsin)\
**Post date:** [November 12, 2025, 12:59pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998/1 "2025-11-12T12:59:17Z")

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Hello everyone,

I’m trying to use TigerVNC to connect to a virtual HMI running on my PC, but instead of showing the HMI display, TigerVNC mirrors my entire computer screen — it looks like a screen duplication rather than the HMI interface.

Has anyone encountered this problem before?

Here are some details:

What’s happening: When connecting via TigerVNC, it displays my Windows desktop instead of the virtual HMI window.

What I’ve tested: I’ve tried adjusting TigerVNC settings, window modes, but the issue remains.

Software / hardware: Automation Runtime version 4.7.7.74 SP, running a virtual HMI instance locally on the same PC.

Any suggestions or configuration tips to make TigerVNC display only the HMI screen properly would be greatly appreciated.

Thanks in advance!

Hamsin

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**Author:** ![christoph.hilchenbac](https://dub1.discourse-cdn.com/brcommunity/user_avatar/community.br-automation.com/christoph.hilchenbac/32/423_2.png) [@christoph.hilchenbac](https://community.br-automation.com/u/christoph.hilchenbac)\
**Post date:** [November 12, 2025, 1:54pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998/2 "2025-11-12T13:54:51Z")

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There is probably already a VNC server running on your PC and now using the 5900 port.

You could try to change the port on your ArSim to 5901 and use that in the VNC client.

 ![image](https://europe1.discourse-cdn.com/brcommunity/original/2X/a/a37f7edec76a7a2be7e3dbe7e59e622d7fe05fe8.png)

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**Author:** ![Hamsin](https://avatars.discourse-cdn.com/v4/letter/h/FF8800/32.png) [@Hamsin](https://community.br-automation.com/u/Hamsin)\
**Post date:** [November 12, 2025, 2:14pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998/3 "2025-11-12T14:14:05Z")

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Many thanks for your detailed explanation.  
Changing the VNC port to **5901** solved the issue completely.  
The virtual HMI now displays correctly in TigerVNC.  
Much appreciated!

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**Author:** ![christoph.hilchenbac](https://dub1.discourse-cdn.com/brcommunity/user_avatar/community.br-automation.com/christoph.hilchenbac/32/423_2.png) [@christoph.hilchenbac](https://community.br-automation.com/u/christoph.hilchenbac)\
**Post date:** [November 12, 2025, 2:25pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998/4 "2025-11-12T14:25:37Z")

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Glad I could help.

But think about deactivating the local VNC server on your PC since this could be security issue 🙂

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**Author:** ![Matt\_Buck](https://avatars.discourse-cdn.com/v4/letter/m/FF8800/32.png) [@Matt\_Buck](https://community.br-automation.com/u/Matt_Buck)\
**Post date:** [November 17, 2025, 12:33pm UTC](https://community.br-automation.com/t/tigervnc-mirrors-my-entire-pc-screen-instead-of-showing-the-virtual-hmi/8998/5 "2025-11-17T12:33:00Z")

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@christoph.hilchenbac there are lots of 3rd party IT administration programs that have prepackaged VNC into them for it’s cross platform compatibilities over RDP. At my last company we got the IT department to reconfigure the software they were using to use a custom VNC port instead of the default 5900 or just set the programs to use 5901 as well.