Many of our projects (student projects as well as research projects) run on one of our local machines, for example on vulcano.informatik.privat:8400, but should be accessible from the outside, for example via http://aqqu.cs.uni-freiburg.de/proxy-test. This is non-trivial, if the latter URL is not only a top-level URL, like http://aqqu.cs.uni-freiburg.de but contains a path, like the /proxy-test.
Apache Config
The first step is to find out, which virtual host deals with the domain. In the example above, it's the Apache virtual host configured in filicudi:/etc/apaches2/sites-available/aqqu.conf and it contains (among others) the following lines:
<VirtualHost *:80> ServerName aqqu.informatik.uni-freiburg.de ServerAlias aqqu aqqu.cs.uni-freiburg.de [...] ProxyPass /proxy-test http://vulcano.informatik.privat:8400 ProxyPassReverse /proxy-test http://vulcano.informatik.privat:8400 [...] </VirtualHost>
The effect of the ProxyPass line is that when somebody types http://aqqu.cs.uni-freiburg.de/proxy-test/<something> in the browser, then vulcano.informatik.privat:8400 gets the request /<something>. Note that details like a trailing / or not in the line in the configuration file are important.
TODO: explain the effect of the ProxyPassReverse line and why and when it is needed.