When you try to connect to VCenter Server Appliance 6.5 U1 with the VMware vSphere Client you get the following error message :-
The required client support files cannot be retrieved from the server 0.0.0.0. The login process will now exit
Details: the request failed because of a connection failure. (Unable to connect to the remote server)
The desktop vSphere Client was deprecated in vSphere 6.5 and is no longer supported. When you try to connect to an ESXi 6.5 host you get the above error message. The Windows based vSphere Client is not supported anymore with this version – full details here.