I was using vSphere Client to connect my ESXi 6 server, but can't attach to any virtual machine console via Internet.
vSphere Client has error message:
Unable to connect to the MKS: Login(username/password) incorrect
Can telnet the ESXi 443 and 902 port.
Best Answer
As far as I remember, solved this issue by allowing few ports by host firewall (902, 903, 443). Make sure it isn't blocked on both sides.
Also, there are some options here https://communities.vmware.com/thread/238478