ok I've found this info, but don't know how to apply it to Mac OS X Server?
Next, you will need to configure Apache to run as a reverse proxy for the Rumpus domain name. The configuration depends on your version of Apache. For Apache 1.X, the configuration will look something like this:
LoadModule proxy_module libexec/httpd/libproxy.so
AddModule mod_proxy.c
<VirtualHost *:80>
ServerName files.acmewidgets.com
ProxyPass /
http://files.acmewidgets.com:8000/
ProxyPassReverse /
http://files.acmewidgets.com:8000/
</VirtualHost>
For Apache 2.X, the configuration is a bit different, as shown here:
LoadModule proxy_module libexec/apache2/mod_proxy.so
<VirtualHost *:80>
ServerName files.acmewidgets.com
ProxyRequests Off
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
ProxyPass /
http://files.acmewidgets.com:8000/
ProxyPassReverse /
http://files.acmewidgets.com:8000/
</VirtualHost>