Why did not connect?

When you attempt to open a virtual machine console from the vSphere Web Client, the console does not
connect. The following error message appears:HTTP ERROR 404
Problem accessin/.Reason:
Not Found
Why did not connect?

A.
Port 443 is in use.

B.
Port 9443 is in use.

C.
Port 8443 is in use.

D.
Port 22443 is in use.

Explanation:
Another program or process is using port 9443, the default port used by the HTML5 virtual machine console.
https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.troubleshooting.doc/GUID-
8536C14F-4D4F-4674-846E-08BE321B7A11.html