Using Server Variables

Introduction. In any web interaction there is a large variety of information that is passed. When a developer wants to access this information it is usually identified by using the name Server Variables.

This information or server variables is usually classified into two major categories

HTTP Headers are pieces of information that are sent from the client to the server when requesting a piece of information or from the server to the client when responding to a page request. For example,

the hostname of the client computer

the browser type and version of the client

the operating system of the client

the type of connection established between the client and the web server

Environment Variables are bits of information that the web server makes available to any program that requests them. For example,

the URL of the ASP page

the entire physical path of the currently executing ASP

the root directory of the web

the web servers computer name

the web server's software

This information can be accessed within an ASP by using an appropriate Request.ServerVariables command. The names of the Server Variables are given in the following two tables.

HTTP Header	Description
HTTP_ACCEPT	A list of the MIME types the client will accept
HTTP_ACCEPT_LANGUAGE	What type of languages the browser expects. These are human languages such as en-us to represent English, United States.
HTTP_CONNECTION	The type of connection established between the client and the web server.
HTTP_HOST	The hostname of the web server.
HTTP_USER_AGENT	The browser type and version, and operating system of the client.
HTTP_REFERER	The full URL of the web page containing the hyperlink used to reach the currently executing ASP page.
HTTP_COOKIE	The cookies sent from the browser.

Environment Variable	Description
URL	The URL of the ASP page between http://www.yourWebServer.com/ and any query string.
PATH_INFO	The same as the URL environment variable.
PATH_TRANSLATED	The full, physical path of the currently executing ASP.
APPL_PHYSICAL_PATH	The physical address of the web's root directory.
QUERY_STRING	The querystring.
SERVER_NAME	The web server's computer name.
SERVER_SOFTWARE	The name of the web server software.

HTTP Headers. Now we want to develop a small ASP that requests some of the HTTP headers and displays them. So you want to copy the following code into a file called SomeHTTPHeaders.asp and upload it back to your ASP web.

<%@ Language=VBScript %>
<% Option Explicit %>

<html>

All of the MIME types the client will accept = <%= request.servervariables("HTTP_ACCEPT") %> 
All languages the browser accepts = <%= request.servervariables("HTTP_ACCEPT_LANGUAGE") %> 
The type of connection = <%= request.servervariables("HTTP_CONNECTION") %> 
The hostname of the client = <%= request.servervariables("HTTP_HOST") %> 
The client's type of browser and operating system = <%= request.servervariables("HTTP_USER_AGENT") %> 
The URL of the referring page = <%= request.servervariables("HTTP_REFERER") %> 

</html>

The meaning of the code will be discussed in class.

Now you would get something like the following screen when you view the page.

Environment Variables. Now we want to develop a similar ASP for displaying some important Environment Variables. You should create a file called SomeEnvironmentVariables.asp and copy in the following code.

<%@ Language=VBScript %>
<% Option Explicit %>

<html>

Physical path to the Webs Root Directory = <%= request.servervariables("APPL_PHYSICAL_PATH") %> 
Physical Path to the folder of the ASP that is currently running = <%= request.servervariables("PATH_TRANSLATED") %> 
The web server's computer name = <%= request.servervariables("SERVER_NAME") %> 
The web server's operating system = <%= request.servervariables("SERVER_SOFTWARE") %> 

</html>

The meaning of the code will be discussed in class.

You should get a screen that looks something like the following.