I started to have this issue as well recently.
The cause of problem for me is a little bit different. and I m posting here for some other people's reference.
I found out that at the end, it's our network problem because I m on VPN.
Port 902/903 is blocked I believe.
I've asked a coworker of mine (not in VPN) and he can successfully telnet to the ESX --> telnet <ESX IP> 902
But I can't while I am on VPN, even if I disabled all firewall.
So I contact the IT dept and they resolved this.
Hope this helps some people.