I have just done this.
The method I used involved installing Apache and Webmin
1. Install Apache, use the following command via putty
apt-get install apache2
Then install webmin, see the following link for how to do this
http://www.webmin.com/deb.html
Then in webmin, goto servers->apache server->Virtual server on Port 80->Alias and redirects-> then in Permanent URL redirects put '/' (without the quotes) in the from field,and the url you wish them to goto ie
https://vpn.mydomain.com
Hope that helps