Server Script Debugging

Understanding how scripts in ASP pages are processed and how errors are handled can help you debug server scripts successfully. To debug server scripts ù scripts in ASP pages ù you run Microsoft Script Debugger on Microsoft Internet Information Server (IIS), version 4.0 or higher, and attach it to a currently running document.

Note To debug client scripts, you must run Microsoft Script Debugger on the same computer that is running Microsoft Internet Explorer. For more details, see Client Script Debugging.

Processing Server Code

Script in an ASP page is not event-driven. Instead, when the page is requested, the server reads the page and processes all server script from top to bottom. This includes code that is inline with HTML text, as shown in the following diagram.

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Because all code in the ASP page is processed as soon as the page is requested, both syntax errors and runtime errors are caught immediately.

A special case for server scripts is the Global.asa file. The Application_OnStart and Session_OnStart procedures in this file are executed only once for an application and for a session. Therefore, you must embed debugging statements in the file. For details, see Debugging the Global.asa File.

Using the Script Debugger With Server Code

To use Microsoft Script Debugger, you must be sure that the debugger is enabled. For details about enabling and disabling the debugger for IIS, see ôDebugging ASP Scriptsö in the IIS documentation.

If the debugger is enabled:

• When the ASP-based application encounters an error (syntax or runtime) in an ASP page, the server stops processing and starts the debugger.
  
  
• Error information is displayed in message boxes on the server. If there is a syntax error, no content is sent to the client browser. If there is a runtime error, only the portion of the content up to the error is sent to the client browser.

  Note If the debugger is enabled on the server, someone must attend the server to view and acknowledge error messages.

If the debugger is disabled:

• Error information is sent to the client browser and appears in the text of the page. It does not appear in a message box.
  
  
• You cannot invoke the debugger at all on the server.

See Also

Debugging Scripts

Starting Microsoft Script Debugger