Almost every VNC Viewer connection problem falls into one of a few buckets: the server isn't running, the network is blocking it, or a display setting is getting in the way. Work through these in order and you'll usually be back in business within minutes.
When you can't connect at all
- Confirm the server is running on the host — look for its tray icon.
- Check the IP address. Run
ipconfigon the host and re-type it exactly. - Allow the port through Windows Firewall on the host machine.
- Verify both PCs are on the same network for local testing.
- Restart the VNC Viewer service if it's installed as a service.
'Connection refused' or timeouts
A refused connection usually means nothing is listening on the port you tried. Confirm the server is actually started, that you're using the right port, and that antivirus or a corporate firewall isn't silently blocking it.
Black screen after connecting
This is a classic VNC symptom, usually tied to display or driver behaviour. Try toggling the mirror-driver option in the server settings, updating the graphics driver, or switching the capture method. On some systems the secure desktop (login screen) requires the server to run as a service.
Password keeps being rejected
- Re-enter it carefully — VNC passwords are case-sensitive.
- Check whether you're hitting the view-only vs full-control password.
- Reset the password in the server properties and try again.
Session connects but is slow
Lag is a settings problem, not a fault. Drop the colour depth, raise compression and pick an efficient encoding in the viewer. Our performance guide has the exact combination to try first.
Frequently asked questions
Usually a display-driver or capture-method issue. Toggle the mirror driver, update graphics drivers, or run the server as a service so it can see the secure desktop.
Make sure the server is running and listening on the expected port, and that no firewall or antivirus is blocking it.
Check for case sensitivity and whether you're entering the view-only password. Resetting it in the server properties usually resolves it.
Remember: always download VNC Viewer from the
official project source, keep it updated, and never expose a raw VNC port to the
internet without a VPN or SSH tunnel. When you're ready,
head to the download section.
