Web servers

There are a multitude of different web servers available. The most popular one is that made by Apache - see http://httpd.apache.org/ for details, and also links to (free) binary versions for Windows (obtain a file ending with a msi extension - double clicking on it will set up and install Apache).

The operation of the web server is controlled by certain configuration files - the main one is called httpd.conf, which resides under a conf subdirectory underneath the top-level directory under which you installed Apache. There are many directives contained in this file - we shall highlight a few of them here, and leave it to the Apache documentation to provide further details.

• ServerRoot "D:/www/Apache2"
  This gives the top-level directory under which all further files relevant to the operation of the web server are found.
• DocumentRoot "D:/www/Apache2/htdocs"
  This gives the top-level directory under which all pages to be served by the web server are found. For example, a request for http://localhost/projects/index.html will send a file index.html contained in a projects subdirectory found under D:/www/Apache2/htdocs. Note that localhost is an alias that you can use for any local computer. Also note that, in the context of a web server, directories are separated by a forward slash (/).
• ScriptAlias /cgi-bin/ "D:/www/Apache2/cgi-bin/"
  This directive does two things. It first allows scripts placed under D:/www/Apache2/cgi-bin/ can be executed, and secondly, sets up an alias that such scripts are accessed as http://localhost/cgi-bin/script_name. This is valuable from the point of view of security - allowing a remote user to execute a program on another machine opens up a whole host of security concerns, and the ScriptAlias directive ensures that only scripts living beneath a certain directory can be run.