Multiple websites on server setup (different domain names)

I want to set up a single web server which runs multiple websites, kind of
like a web host does. I also want them to be accessable by different domain
names, how do i go about doint this? All i know how to do is set up a root
one on port 80 to be the website, but of course the other sites would be on
differnt ports for each site... how would you go about mapping this through
domain names? thanks


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