For the most common case of lots of users needing ports (web apps), there's the option in nginx and newer Apache versions to proxy to a UNIX socket, so no port

For the most common case of lots of users needing ports (web apps), there's the option in nginx and newer Apache versions to proxy to a UNIX socket, so no port is needed for the user app. It's not gonna work for everything but many web app servers are fine with using a socket instead of a port. There's also http://cyberelk.net/tim/software/portreserve/ http://cyberelk.net/tim/software/portreserve/ for when ports are really needed (not as elegant as the solution under discussion, though, as it just holds a port by binding to it until the rightful owner/service comes along).