Set http port 777 for subdomain

I have been searching the web for an answer to this question but I couldn't find anything.

I have a CentOs server managed with Plesk 12.5, with a 2nd level domain mysite.com for which I have created a number of subdomains (3rd level) sd1.mysite.com, sd2.mysite.com, etc.
The web server is Apache and also NGix is installed and working.

All the subdomains are reachable from the web : e.g. http://sd1.mysite.com, through port 80.

For one of these subdomains, I need it to be...

Set http port 777 for subdomain