(be sure this second port is available to you through any firewall you may have)
In your mapping table ("Web request mapping (redirects)"), per the examples included there, set it up so any requests to the normal web port are redirected to an HTML page.
where test.html is an HTML file located in your root HTML directory (by default this is the 'HTML' subdirectory of 'webx').
Then to do your work on the server, you access your site through the 8080 port
When you are done, remove the new mappings and if you wish, close the alternate port access.