I started to see errors on our calls to the Xero API, with status 412 returned. The initial clue was in this Xero Community post.

On windows 7 machines or older machines, you may need to install a fix to ensure that windows can handle TLS 1.1 or 1.2. I usually recommend this update as a first step as it mitigates not knowing how the underlying code, wrapper may work.

This led me to a post about TLS versions, with a useful piece of code to check the TLS version of your server:

<%
Set objHttp = Server.CreateObject("MSXML2.ServerXMLHTTP.6.0")
objHttp.open "GET", "https://howsmyssl.com/a/check", False
objHttp.Send
Response.Write objHttp.responseText 
Set objHttp = Nothing 
%>

Running this I found the particular VM was showing TLS1.0, which is not good. I recalled I’ve seen something similar a few weeks ago on another project which was calling the Vimeo API, which now requires TLS1.2 or above.

This particular server is 2008 R2, and there’s a patch to upgrade your TLS to 1.2.

I used the Windows Catalog Update link in the article plus used the Registry EasyFix to sort the registry key out.

Now the TLS test code above is returning

"tls_version":"TLS 1.2"

And my calls to the Xero API are working.

In Classic ASP there is the function isNumeric, which one uses to test if a value is a number. So for example:

Response.write IsNumeric("21")  // true
Response.write IsNumeric("David")  // false

Seems straightforward so far. Then you try this:

Response.write IsNumeric("15447D")  // true

Every so often this little quirk would popup. This morning it’s been driving me mad because I had a set of string values that were mixtures of alphanumeric, or numeric values. I wanted to discriminate between numbers and not-numbers and store the values in different columns in a database table. Using isNumeric though kept throwing errors – it tested 15447D as being a number, and of course once I tried to insert that into an integer column an error was thrown.

Finally figured how what’s happening after a little digging online. isNumeric also considers hex values to be valid numbers. 15447D is hex for 1393789. Now the lights go on – only wondered about this for 20 years.

Apparently this is also the case for octal values.

So a custom function along these lines is the answer:

Function myIsNumeric(ByVal Value)
	Dim regEx
	Set regEx = New RegExp
	regEx.pattern = "^(0|[1-9][0-9]*)$"
	myIsNumeric = Regex.Test(Value)
End Function