Failed to read from SSL socket: The TLS connection was non-properly terminated

[Oton Marques Jr.]

I can connect to my company's vpn using cisco's client, but when I try
it using openconnect (with servercert parameter), I  get the
following:
--
$ openconnect GATEWAY-IP --servercert <pin-sha256>
Connected to GATEWAY-IP:443
SSL negotiation with GATEWAY-IP
Server certificate verify failed: signer not found
Connected to HTTPS on GATEWAY-IP
Failed to read from SSL socket: The TLS connection was non-properly terminated.
Error fetching HTTPS response
GET https://GATEWAY-IP/
Connected to GATEWAY-IP:443
SSL negotiation with GATEWAY-IP
Server certificate verify failed: signer not found
Connected to HTTPS on GATEWAY-IP
Failed to read from SSL socket: The TLS connection was non-properly terminated.
Error fetching HTTPS response
Failed to obtain WebVPN cookie

I could keep using cisco's client but I'd prefer to use openconnect so
I could connect using network manager on xfce, so any help would be
much appreciated.

Regards
Oton