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Web server applications

Posted on 2001-06-15
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Last Modified: 2010-04-06

How will I write a web server application in Delphi?.What should be the type of the webserver application?.
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Question by:mrk_raj
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by:inthe
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by:Mohammed Nasman
ID: 6197622
Hello

  with Delphi you can build web server app in three methods: CGI, ISAPI, and ASP, I prefer the ISAPI cuz it's the fastest method of them

if you need to develop ur application with cgi or isapi, see my comment and the other comments in this question

http://www.experts-exchange.com/jsp/qShow.jsp?ta=delphi&qid=20127095

Mohammed
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Motaz earned 30 total points
ID: 6197949
CGI Stand-alone: Is an executable file that uses the standard input/ouput (Consoles) to receive and send data.

Win-CGI: Designed specially for Visual Basic because VB cann't talk directly to standard input/output ports, so that instead the Win-CGI receive and send data using temporary ini files which causes intensive use of hard disk.

ISAPI/NSAPI: (Internet Server API/Netscape Server API) Both are DLL's that work with Microsoft servers/Netscape servers respectively. The good news is that Delphi produce one DLL that can be work with both servers, so that we will refered by ISAPI to both kinds of DLLs.

Comparison:
The most important difference between ISAPI and CGI is that the server launchs new instance of the CGI executable for each request, for example if there is a 7 concurrent users, the server will load 7 instances of the same CGI. This is the most biggest disadvantage of the CGI, because it leads to memory consumption and reduce server performance when the request number increased.
ISAPI loads only once in the memory and it serves all the requests, but it creates separate instances of TWebModule for each request.
The ISAPI is very suitable for large web applications that uses database servers such as Oracle, and Interbase. When the first request received to the web server, it loads the ISAPI DLL and open a connection with database server. When the next request received, there is no need to establish new connection, and the old connection will be used.

In addition to these advantages of ISAPI, there is a drawback of using it.
Since the ISAPI DLL shared for all requests, unhandled error of one request could crash the DLL and hangs the server, and no one else can get a response. In most such cases the DLL must be stopped and started again.
In CGI if an error occures in one request, only it's instance of CGI will be stopped and the others will resume normally.

Motaz
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