ISAPI Server Extensions and Filters

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The Internet Server API (ISAPI) provides a simple and efficient way to extend any ISAPI-compliant Web server.

Advantages of ISAPI Server Extensions

You can write ISAPI server extension DLLs (ISAs) that can be loaded and called by the HTTP server. Users can fill out forms and click a submit button to send data to a Web server and invoke your ISA, which can process the information to provide custom content or store it in a database. Web server extensions can use information in a database to build Web pages dynamically, and then send them to the client computers to be displayed. Your application can add other custom functionality and provide data to the client using HTTP and HTML.

Advantages of ISAPI Filters

You can write an ISAPI filter. The filter is also a DLL that runs on an ISAPI-enabled HTTP server. The filter registers for notification of events such as logging on or URL mapping. When the selected events occur, the filter is called, and you can monitor and change the data (on its way from the server to the client or vice versa). ISAPI filters can be used to provide custom encryption or compression schemes, or additional authentication methods.

Both server extensions and filters run in the process space of the Web server, providing an efficient way to extend the server's capabilities.

What do you want to do?

• Create an ISAPI Extension

• Create an ISAPI Filter

What do you want to know more about?

• Differences between filters, server extensions, and CGI

• Using ISAPI to extend Web servers

• Writing ISAPI Server Extensions

• Writing ISAPI Filters

See Also   Internet First Steps: ISAPI Server Extensions and Filters, Internet Server API (ISAPI) Extensions