Sitemap & robots file for subdomain meteor

I am creating an app using meteor that creates dynamic subdomain how meteor does like
example.meteor.com/
telescope.meteor.com/
example2.meteor.com/
Now i am willing to create sitemap and robots.txt for each url that is not given for meteor subdomain
example.meteor.com/sitemap.xml & example.meteor.com/robots.txt
telescope.meteor.com/sitemap.xml & telescope.meteor.com/robots.txt
example2.meteor.com/sitemap.xml & example2.meteor.com/robots.txt

I am using gadicohen:sitemaps for sitemap creation .
My problem-
I am able to get hostname using window.location.host . but how can i get it serverside to fetch subdomain .

Take a look at my comments in this thread:

Hi @hwillson, do you have any suggestions for robots.txt for subdomains? Since it’s the same codebase - I haven’t been able to figure this part out…