Troubleshooting port 443 conflict caused by Windows Admin Center

When Windows Admin Center is installed on the same server as Cayosoft Guardian, it may use TCP port 443 by default through http.sys. If Cayosoft Guardian is installed afterward and attempts to use the same HTTPS port for the web portal, a port binding conflict can occur and the Cayosoft Guardian web portal service may fail to start.

Applies to

• Cayosoft Guardian web portal
• Windows Admin Center installed on the same server

Symptoms

• The Cayosoft Guardian web portal is not accessible after installation.
• The Cayosoft Guardian service or web portal service fails to start.
• Port 443 is already in use on the server.
• Service startup logs or Windows event logs indicate that the HTTPS listener could not bind to the configured port.

Root cause

Windows Admin Center uses port 443 by default and registers its listener through http.sys. If Cayosoft Guardian is configured to use the same HTTPS port on the same server, only one service can bind to that port. As a result, Cayosoft Guardian cannot start its web portal listener.

Resolution

Reconfigure Windows Admin Center to use a different HTTPS port, then restart Cayosoft Guardian.

1. Confirm that Windows Admin Center is installed on the same server as Cayosoft Guardian.
2. Confirm that the Cayosoft Guardian web portal is configured to use port 443 (or identify the configured HTTPS port if different).
3. Re-run the Windows Admin Center installer (or setup) on the server.
4. When prompted for the HTTPS port, select an unused port other than 443.
   • Choose a port that is approved by your organization and not already in use.
   • Document the selected port for administrators who use Windows Admin Center.
5. Complete the Windows Admin Center setup/update.
6. Restart the Windows Admin Center service if required by the installer.
7. Restart the Cayosoft Guardian service (or restart the server if needed).
8. Verify that the Cayosoft Guardian web portal starts successfully and is reachable.
9. Run the following command from an elevated Command Prompt or PowerShell session:

netstat -ano | findstr :443To review HTTP.sys SSL bindings, run:
netsh http show sslcert

To prevent this:

• Do not assign port 443 to multiple web services on the same server.
• Plan port assignments before installing Windows Admin Center and Cayosoft Guardian on the same host.
• Record custom Windows Admin Center port assignments in deployment documentation.