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Encyclopedia > ISAPI

The Internet Server Application Programming Interface (ISAPI) is an N-tier API of Internet Information Services (IIS), Microsoft's collection of Windows-based web server services. The most prominent application of IIS and ISAPI is Microsoft's web server. In computing, Three-tier is a client-server architecture in which the user interface, functional process logic (business rules) and data storage and data access are developed and maintained as independent modules, most often on separate platforms. ... API and Api redirect here. ... Microsoft Internet Information Services (IIS; formerly called Server) is a set of Internet-based services for servers using Microsoft Windows. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... Windows redirects here. ... The inside/front of a Dell PowerEdge web server The term Web server can mean one of two things: A computer program that is responsible for accepting HTTP requests from clients, which are known as Web browsers, and serving them HTTP responses along with optional data contents, which usually are...

ISAPI Filters dialog in Microsoft IIS
ISAPI Filters dialog in Microsoft IIS

The ISAPI has also been implemented by Apache's mod_isapi module so that server-side web applications written for Microsoft's IIS can be used with Apache. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The Apache HTTP Server, commonly referred to simply as Apache, is a web server notable for playing a key role in the initial growth of the World Wide Web. ...

Contents

Big Picture

The word "server" can refer to a computer ( "box" ) or a piece of software ( for example, SQL Server ). Microsoft's web server application is called Internet Information Services, which is made up of a number of "sub-applications" and is very configurable. ASP.NET is one such slice of IIS, allowing a programmer to write web applications in his or her choice of programming language ( Visual Basic, C#, J# ) that's supported by the Microsoft .NET CLR. ISAPI is a much lower-level programming system, giving much better performance, at the expense of complexity. While Microsoft is generally credited with the creation of the ISAPI specification, it was actually codeveloped by Process Software and Microsoft with input from a small number of other vendors.[1] Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... Microsoft Internet Information Services (IIS; formerly called Server) is a set of Internet-based services for servers using Microsoft Windows. ... ASP.NET logo ASP.NET is a web application framework marketed by Microsoft that programmers can use to build dynamic web sites, web applications and XML web services. ...


Performance and compromise

Compared to PHP or ASP, which both are server-side scripting technologies, ISAPI is a real executable part of the system - thus: having the highest performance possible. To issue a statement: A Microsoft webserver executes ASP and PHP by running an ISAPI Server Extension. Comparing PHP/ASP with ISAPI is like comparing Microsoft Office with Microsoft Windows: Office can never run faster than Windows - its operating system - itself. For other uses, see PHP (disambiguation). ... Active Server Pages (ASP) is Microsofts server-side script engine for dynamically-generated web pages. ... Scripting languages (commonly called scripting programming languages or script languages) are computer programming languages that are typically interpreted and can be typed directly from a keyboard. ...


Before switching to ASP.Net Microsoft's MSDN-Library (msdn.microsoft.com) was fully developed with ISAPI. Ebay still uses the "eBayISAPI.dll", although they declare that they are using Java-Technology powered by Sun.[2] The Microsoft Developer Network (MSDN) is an information service from Microsoft for software developers. ...


The greatest disadvantage of developing web applications at ISAPI level is the required development time, which is at least twice as high as using ASP or PHP.[citation needed] Another penalty is the lack of native support for many standard web application features such as Session handling, which are common features in technologies such as ASP and PHP. In computer science, in particular networking, a session is either a lasting connection using the session layer of a network protocol or a lasting connection between a user (or user agent) and a peer, typically a server, usually involving the exchange of many packets between the users computer and...


ISAPI for IIS 5.0 and earlier

In contrast to CGI applications, an ISAPI application is loaded into the same process space as the IIS web server. This removes the need for inter-process calls allowing improved performance of ISAPI applications over CGI applications. However, if an ISAPI application crashes, it can cause the whole of the web server to crash along with it. The Common Gateway Interface (CGI) is a standard protocol for interfacing external application software with an information server, commonly a web server. ... In computing, a process is an instance of a computer program that is being executed. ... A crash in computing is a condition where a program (either an application or part of the operating system) stops performing its expected function and also stops responding to other parts of the system. ...


ISAPI for IIS 6.0

In IIS 6.0 it is possible to configure an IIS application to run in a separate process space created by IIS (recommended mode: "High (isolated)"). Thus, performance is maintainted but if the ISAPI application crashes it will not cause the whole IIS server to crash.


ISAPI applications

ISAPI consists of two components: Extensions and Filters. These are the only two types of application that can be developed using ISAPI. Both Filters and Extensions must be written in C++ and compiled into DLL files which are then registered with IIS to be run on the web server.


ISAPI applications can be written using C++ and Delphi Pascal. There are a couple of C++ libraries available which help to ease the development of ISAPI applications, and in Delphi Pascal the Intraweb components for web-application development. MFC includes classes for developing ISAPI applications. Additionally, there is the ATL Server technology which includes a C++ library dedicated to developing ISAPI applications. This article does not cite any references or sources. ... ATL Server is a technology for developing web based applications. ...


Extensions

ISAPI Extensions are true applications that run on IIS. They have access to all of the functionality provided by IIS. ISAPI extensions are implemented as DLLs that are loaded into a process that is controlled by IIS. Clients can access ISAPI extensions in the same way they access a static HTML page.


Filters

ISAPI filters are used to modify or enhance the functionality provided by IIS. They always run on an IIS server and filter every request until they find one they need to process. Filters can be programmed to examine and modify both incoming and outgoing streams of data.


Filters are implemented as DLL files and can be registered on an IIS server on a site level or a global level (i.e., they apply to all sites on an IIS server). Filters are initialised when the worker process is started and listens to all requests to the site on which it is installed.


Common tasks performed by ISAPI filters include:

  • Changing request data (URLs or headers) sent by the client
  • Controlling which physical file gets mapped to the URL
  • Controlling the user name and password used with anonymous or basic authentication
  • Modifying or analysing a request after authentication is complete
  • Modifying a response going back to the client
  • Running custom processing on "access denied" responses
  • Running processing when a request is complete
  • Run processing when a connection with the client is closed
  • Performing special logging or traffic analysis.
  • Performing custom authentication.
  • Handling encryption and compression.

Common ISAPI applications

This is a list of common ISAPI applications implemented as ISAPI extensions:

  • Active Server Pages (ASP), installed as standard
  • ASP.NET, installed as standard on IIS 6.0 onwards
  • Perl ISAPI (aka PerlIIS), available for free to install
  • PHP, available for free to install.

Active Server Pages (ASP) is Microsofts server-side script engine for dynamically-generated web pages. ... ASP.NET logo ASP.NET is a web application framework marketed by Microsoft that programmers can use to build dynamic web sites, web applications and XML web services. ... Wikibooks has a book on the topic of Perl Programming Perl is a dynamic programming language created by Larry Wall and first released in 1987. ... For other uses, see PHP (disambiguation). ...

ISAPI Development

ISAPI applications can be developed using any development tool that can generate a Win32 DLL. Wizards for generating ISAPI framework applications have been available in Microsoft development tools since Visual C++ 4.0.


See also

Microsoft Internet Information Services (IIS; formerly called Server) is a set of Internet-based services for servers using Microsoft Windows. ... ATL Server is a technology for developing web based applications. ... In computer science, the Server Application Programming Interface (SAPI) is the generic term used to designate direct module interfaces to web server applications such as the Apache HTTP Server, Microsoft IIS, or iPlanet. ... C++ (pronounced see plus plus, IPA: ) is a general-purpose programming language with high-level and low-level capabilities. ... For other uses, see PHP (disambiguation). ...

Footnotes

  1. ^ http://wasd.vsm.com.au/ht_root/doc/scripting/scripting_0600.html
  2. ^ eBay was initially developed using Microsoft technology for both the front end and back and processing (re: The Perfect Store by Adam Cohen). They later adopted a Java application server for the request processing but the web client software still uses an ISAPI application.

References

  • The Perfect Store, Adam Cohen, ISBN 0749924039

External links

  • The ISAPI Developer's site
v • d • e
Web server interfaces
General Common Gateway Interface (CGI) · Simple CGI · FastCGI
Technology specific ISAPI · Java Servlet · NSAPI · AJP · Python WSGI
Apache modules mod_perl · mod_php · mod_python · mod_ruby

  Results from FactBites:
 
mod_isapi - Apache HTTP Server (862 words)
ISAPI extension modules (.dll files) are written by third parties.
Whether or not you have preloaded an ISAPI extension, all ISAPI extensions are governed by the same permissions and restrictions as CGI scripts.
Many ISAPI modules are subtly incompatible with the Apache server, and unloading these modules helps to ensure the stability of the server.
ISAPI Extension Overview (1001 words)
ISAPI extensions are true applications that run on IIS and have access to all of the functionality provided by IIS.
ISAPI extensions are implemented as DLLs that are loaded into a process that is controlled by IIS.
The ISAPI extension carries out the actions it was designed to perform: for example, reading more data from the client (as in a POST operation), or writing headers and data back to the client.
  More results at FactBites »


 

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