vCenter Server uses TCP port 443 to listen for data transfer from its clients by default. If you have a firewall between vCenter Server and its clients, you must configure a connection through which vCenter Server can receive data from the clients.

Open TCP port 443 in the firewall to enable vCenter Server to receive data. Firewall configuration depends on what is used at your site, ask your local firewall system administrator for information.

If you do not want to use port 443 as the port for vSphere Web Client-to-vCenter Server communication, you can switch to another port. How you open ports depends on whether you use a vCenter Server Appliance or a vCenter Server Windows installation.

If you are still using the VMware Host Client, see the vSphere Single Host Management - VMware Host Client documentation.