Port 80 is generally/normally used for HTTP, not telnet. Although you are using telnet on your side the other side is a web server and expecting HTTP commands. I know how to type HTTP commands using a telnet client, but I don't know how to pass the userid and password for authentication.
What I think you need to do is setup the firewall so that you can http directly to the lacie box and then use a normal web browser to do this.