How to Build Your Own Website Uptime Monitoring Script using VBScript: Part 1

Website Uptime Monitoring: The Basics

There are lots of website uptime monitoring services out there but all the components you need to build your own website monitoring tool can be found in good ole’ Microsoft VBScript.

Stop laughing, I’m not kidding!

In this article, I’ll share with you some scripts and tips I’ve used successfully in the past for monitoring website uptime even if your website is running in a complex load balanced enterprise environment which some of mine are.

VBScript Components for Uptime Monitor

Most people don’t know that VBScript can make Ajax HTTP calls but it can.

We will use VBScript’s ability to make Ajax HTTP calls to our website to see if it responds then put some simple logic around that response to log the results in a text/csv file.

It really is amazingly simple once you get all the code components together.

The ISWebSiteUp Function

The ISWebsiteUp function takes a URL string and makes an Ajax HTTP call to see if we get a HTTP code 200 or 404 returned meaning website loaded OK.

Once we get our 200 or 404 HTTP response code that, script returns true in the form of a text message box or if script times out you’ll get a false in an error message box.

You might be saying to yourself about now, what about the 404 response code for page not found. Yes, you might want to add some more code to handle that differently than a 2oo OK response but for this script, we just want to know if server is up. If we are pointing to a page at the root of a domain, we don’t typically get 404 errors in reality.

The Script Code

To use this code, copy it in to a text file and save it with a .vbs file extension for VBScript. Once you have the .vbs file, double click on it and you should get a message box with the names of the logged in user on the specified Windows PC on your network.


'isWebsiteUp: Takes String URL 
'isWebsiteUp: Returns strMessage in Message Box
Function isWebsiteUp(strURL)

	On Error Resume Next

	Set http = CreateObject("MSXML2.ServerXMLHTTP")
 	'Set http = CreateObject("Microsoft.XmlHttp")
	http.open "GET", strURL, False
	http.send ""

	'Only check for error of the HTTP Get request for 200 or 404 code returned. If any status is returned then the server is up
	if http.responseText <> "" AND err.number = 0 then
		'Commented out showing the response text. Use this for troubleshooting or exploring.
		'msgbox(http.responseText)
		isWebsiteUp = true
		strMessage = "is up"
	else
		isWebsiteUp = false
		strMessage = "is down"
	end if
	Set http = Nothing	

	msgbox(strURL & ":" & strMessage)
	err.clear
End Function

call isWebsiteUp("https://www.google.com") 

What the Web Server Sees in the HTTP call: WinHTTPRequest User Agent

The VBScript Ajax HTTP call to the web server presents itself as a web browser asking for the home page.

In the server logs a server admin may see this “User Agent” in their logs.

Mozilla/4.0 (compatible; Win32; WinHttp.WinHttpRequest.5)

Script Errors & Blocked HTTP Calls

This script works out of the box. Google is the most open website in the world in terms of IPs that their servers accept traffic from as they are in the business of collecting data about everything including every system that connects to it.

Other web servers, like ones I run, may not be so forgiving. Many server admins use many tools at their disposal to filter HTTP request at various levels.

Here are some examples of tools Windows Server Admin have at their disposal to block or filter your script from connecting to their web servers.

Windows Server Admin Tools for Handling HTTP Traffic

  • Firewall IP Restrictions (Window Server Admin)
  • HTTP Response Filtering (IIS Application Server Admin)
  • IP Restrictions (IIS Application Server Admin)

VBScript Error – MSXML3.dll error ‘800C0005’

This is a popular re-post from my old Blogger blog.

I’m working on  a website up-time monitoring script.

After I had my initial prototype working, I received more requirements for logging output to CSV in addition to storing output in Access DB and decided to add CPU usage percentages to the logging.

Once I had all that done, I started getting odd errors when solution should be detecting a down-time event.

Testing the script with older version of Microsoft.XmlHttp had issues where certain but not all websites the script would call were incorrectly displaying HTTP status code 404 but a 200 OK was really sent back verified by using Fiddler.  Very odd behavior.

The error is related to VBScript’s use of the older version of the Microsoft.XmlHttp object.

The Code

Function isPortalOffline(strURL)
 'Set WshShell = WScript.CreateObject("WScript.Shell")
 Set http = CreateObject("Microsoft.XmlHttp")

 http.open "GET", strURL, False
 http.send 
 
 'Only check for error of the http Get request
 if err.Number <> 0 Then
  isPortalOffline = True
 Else
  'Wscript.Echo "error" & Err.Number & ": " & Err.Description
  isPortalOffline = False
 End If

 'Clear the error after setting isPortalOffline
 err.clear
 'set WshShell = Nothing
 Set http = Nothing 

 ReportError("isPortalOffline")
End Function

Error: MSXML3.dll error ‘800C0005’ The System cannot locate the resource

Changed MSXML Objects.

The Fixed Code

Replaced Microsoft.XmlHttp with MSXML2.ServerXMLHTTP.

Function isPortalOffline(strURL)
 'Set WshShell = WScript.CreateObject("WScript.Shell")
 Set http = CreateObject("MSXML2.ServerXMLHTTP")

 http.open "GET", strURL, False
 http.send
 
 'Only check for error of the http Get request
 if err.Number <> 0 Then
  isPortalOffline = True
 Else
  'Wscript.Echo "error" & Err.Number & ": " & Err.Description
  isPortalOffline = False
 End If

 'Clear the error after setting isPortalOffline
 err.clear
 'set WshShell = Nothing
 Set http = Nothing 

 ReportError("isPortalOffline")
End Function

This resolved my issues!

I hope this helps someone. 🙂