Each virtual server handles a web site, complete with modules and
module configurations. To make a virtual server reachable by the
outside world, you will have to configure its Server Variables/Listen ports
variable to select which protocol, IP address and port number the
virtual server are to use.
The protocols Challenger support are HTTP, HTTPS and FTP. HTTP, Hyper
Text Transfer Protocol, is the basic protocol used by web servers. The
default port for HTTP is 80.
HTTPS is HTTP over SSL, the Secure Socket Layer, which provides
encrypted communication. The default port for HTTPS is 443.
FTP, File Transfer Protocol, is an older protocol that is still
used for some purposes. The default port for FTP is 21.
IP address and port
All communication over the Internet is channeled through IP addresses
and ports. Each computer handles one or a few IP addresses. For each
IP address, there are 65,535 available ports. Each protocol has its
own default port, which is the preferred port for communication in
Usually, it is possible to use any port by specifying it
explicitly. Thus, the URL http://www.roxen.com/ will use the
default port, 80 in this case, while the URL
http://skuld.idonex.se:4711/ will use the port 4711.
The basic IP addresses consist of numbers, for example
188.8.131.52, that are not particularly easy to
remember. Domain Name System, DNS, helps by suppling symbolic names,
for example www.roxen.com that are translated into the IP
addresses needed for communication.
The symbolic names are handled by name servers. For example,
Idonex's name server handles domain roxen.com, among others.
Configurations of new names under a domain are done by configuring the
Many protocols make it necessary for each information service on the
Internet to have its own IP address. Thus, each web site and FTP site
would need one IP address. If one computer were to handle more than
one information service it would have to handle more than one IP
In HTTP, the web site wanted is also sent through the protocol in
the Host header. Thus, it is possible to make several web sites share
the same IP address and port. When a virtual server in Challenger is
configured for IP-less HTTP, it will have no port of its own. Instead
it will rely on getting requests from another virtual server that does
listen to the port.
Really old browsers such as Netscape 1.0, do not support the Host
header, and therefore can not connect to web sites using IP-less HTTP.
It is strongly recommended to upgrade such browsers.
Each IP address that a computer handles is bound to an interface. An
interface is an ethernet card, a modem, or some other physical network
hardware. A computer, or router, connected to more than one physical
network needs one IP address per network interface.
It is also possible to configure virtual interfaces for the
sole purpose of handling more IP addresses. How this is done varies
between operating systems. If you want to handle more than one HTTPS
or FTP server on each computer, or don't like IP-less HTTP, you will
need to know how to set up additional virtual interfaces.