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The DetectAutoProxyUrl function identifies the auto-config script location

Before you begin:

Internet Explorer has an [x] Automatically detect settings check box. This will cause the browser to search for the configuration file.

If your DomainName is machine.something.meta.net.nz then InternetExplorer will request the following urls until it finds a WPAD configuration file.

http://wpad.something.meta.net.nz/wpad.dat   
http://wpad.meta.net.nz/wpad.dat   
http://wpad.net.nz/wpad.dat   
http://wpad.nz/wpad.dat

WPAD stands for Web Proxy Auto-Discovery.

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Code:

DO decl

LOCAL lcRmScript, lcLocal
lcRmScript = Repli(Chr(0), 250)

* dwDetectFlags = 1, 2
* PROXY_AUTO_DETECT_TYPE_DHCP
* PROXY_AUTO_DETECT_TYPE_DNS_A
IF DetectAutoProxyUrl(@lcRmScript, Len(lcRmScript), 2) = 0
	WAIT WINDOW NOWAIT "Not detected. "
	RETURN
ENDIF

lcRmScript = STRTRAN(lcRmScript, Chr(0), "")

IF Not EMPTY(lcRmScript)
	= MessageB("Location of a WPAD autoproxy script:     " +;
		Chr(13)+Chr(13) + lcRmScript, 64, " DetectAutoProxyUrl")

	WAIT WINDOW NOWAIT "Donwloading from URL... "
	lcLocal = SYS(2003) + "\autoscript.txt"
	URLDownloadToFile(0, lcRmScript, lcLocal, 0,0)
	WAIT WINDOW NOWAIT "Downloaded from " + lcRmScript + "   "

	IF FILE(lcLocal)
		MODI FILE (lcLocal) NOMODI NOWAIT
	ENDIF
ENDIF
* end of main

PROCEDURE decl
	DECLARE INTEGER GetLastError IN kernel32

	DECLARE INTEGER DetectAutoProxyUrl IN wininet;
		STRING @lpszAutoProxyUrl, LONG dwAutoProxyUrlLength,;
		LONG dwDetectFlags

	DECLARE INTEGER URLDownloadToFile IN urlmon;
		INTEGER pCaller, STRING szURL, STRING szFileName,;
		INTEGER dwReserved, INTEGER lpfnCB  

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Listed functions:

DetectAutoProxyUrl
GetLastError
URLDownloadToFile

Comment:

An example of WPAD.DAT file:

function FindProxyForURL(url, host)  
{  
	// We only cache http and ftp  
	if (url.substring(0, 5) == "http:" || url.substring(0, 4) == "ftp:")  
		return "PROXY cache:8080; DIRECT";  
  
	// Otherwise use direct connection  
	return "DIRECT";  
}

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