CODEWITHSUNDEEP
asp.netweb-servicesasp-classic
Steffen Jørgensen
Steffen Jørgensen

Reputation: 312

Server side call to webservice in classic ASP

I've .NET webservice, which takes a encoded html-string as a parameter, decodes the string and creates a PDF from the html. I want to make a synchronous server side call to the webservice from a classic asp webpage. It works fine if use a plain text string (with no html tags), but when I send a encoded html string the webservice it seems that the string is empty when it reaches the webservice.

The webservice is working fine when I call it from client side, with both plain text string and an encoded html string.

My code looks like this:

Private Sub SaveBookHtmlToPdf(pHtml, pShopId) 
    Set oXMLHTTP = CreateObject("Msxml2.ServerXMLHTTP.6.0")        
    Dim strEnvelope
    strEnvelope = "pShopId=" & pShopId & "&pEncodedHtml=" & Server.HTMLEncode(pHtml)
    Call oXMLHTTP.Open("POST", "https://mydomain.dk:4430/PdfWebservice.asmx/SaveBookToPdf", false)
    Call oXMLHTTP.SetRequestHeader("Content-Type","application/x-www-form-urlencoded")
    Call oXMLHTTP.Send(strEnvelope)
    Set oXMLHTTP = Nothing
End Sub

It smells like some kind of security issue on the server. It's working when posting a asynchronous call from the client side, but not when it comes from server side - it seems that the encoded html string is somehow not allowed in a server side call to the webservice.

Anyone who know how to solve this tricky problem?

Upvotes: 1

Views: 2642

Answers (3)

Darkstrumn
Darkstrumn

Reputation: 193

AnthonyWJones made the point about URL encoding and HTML encoding, and the original problem being experienced is likely a combine of the two, a race condition if you will. While is was considered answered, it partially wasn't, and hopefully this answers the cause of the effect.

So, as the message get HTMLEncoded, the html entities for the tags become such '<' = '&lt;'.

And as you may know, in URLEncoding, &'s delimit parameters; thus the first part of this data strEnvelope = "pShopId=" & pShopId & "&pEncodedHtml=" & Server.HTMLEncode(pHtml) upto the "&pEncodedHtml" bit, is fine. But then "<HTML>..." is added as the message, with unencoded &'s...and the receiving server likely is delimiting on them and basically truncating "&pEncodedHtml=" as a null assign: "&pEncodedHtml=&lt;HTML&gt;... ." The delimiting would be done on all &'s found in the URL.

So, as far as the server is concerned, the data for parameter &pEncodedHtml was null, and following it were now several other parameters that were considered cruft, that it likely ignored, which just happened to actually be your message.

Hope this provides additional info on issues of its like, and how to correct.

Upvotes: 0

AnthonyWJones
AnthonyWJones

Reputation: 189467

This looks all wrong to me:

 Server.HTMLEncode(pHtml)

Its quite common for developers to get confused between HTML encoding and URL encoding even though they are quite different. You are posting data that needs to be URL encoded. Hence your code should use URLEncode instead:

 strEnvelope = "pShopId=" & pShopId & "&pEncodedHtml=" & Server.URLEncode(pHtml)

Edit:

One thing that URLEncode does that may not be compatible with a URLEncoded post is it converts space to "+" instead of "%20". Hence a more robust approach might be:

 strEnvelope = "pShopId=" & pShopId & "&pEncodedHtml=" & Replace(Server.URLEncode(pHtml), "+", "%20")

Another issue to watch out for is that the current value of Response.CodePage will influence how the URLEncode encodes non-ASCII characters. Typically .NET does things by default in UTF-8. Hence you will also want to make sure that your Response.CodePage is set to 65001.

 Response.CodePage = 65001
 strEnvelope = "pShopId=" & pShopId & "&pEncodedHtml=" & Replace(Server.URLEncode(pHtml), "+", "%20")

Upvotes: 1

akiller
akiller

Reputation: 2472

This may or may not help but I use a handy SOAP Class for Classic ASP which solved a few problems I was having doing it manually. Your code would be something like this:

Set cSOAP = new SOAP
cSOAP.SOAP_StartRequest "https://mydomain.dk:4430/PdfWebservice.asmx", "", "SaveBookToPdf"
cSOAP.SOAP_AddParameter "pShopId", pShopId
cSOAP.SOAP_AddParameter "pEncodedHtml", Server.HTMLEncode(pHtml)
cSOAP.SOAP_SendRequest
' result = cSOAP.SOAP_GetResult("result")

You will probably need to set your namespace for it to work ("" currently), and uncomment the 'on error resume next' lines from the class to show errors.

Upvotes: 0

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