WinHTTP Request 5.1 error 400 (Bad Request)

[Thomasso]

Hello,

I am trying to integrate creating shipping labels in my Access application. I have good documentation from the carrier and I made the auth request work using the Postman software, as can be seen here:

https://i.imgur.com/9X93SgH.png

https://i.imgur.com/cTcPyWU.png

https://i.imgur.com/bKyv2b1.png

I am trying to replicate this using VBA in Access, with this code:

Public Sub PPLAuth()

    Dim HTTPreq As Object
    Dim URL As String
    Dim strBody As String
    Dim JSON As Object

    Set HTTPreq = CreateObject("WinHttp.WinHttpRequest.5.1")
    
    URL = "https://api-dev.dhl.com/ecs/ppl/myapi2/login/getAccessToken"
    
    HTTPreq.Open "POST", URL, False
    HTTPreq.SetRequestHeader "content-type", "application/x-www-form-urlencoded"
    HTTPreq.SetRequestHeader "user-agent", "PostmanRuntime/7.32.2"
    HTTPreq.SetRequestHeader "accept", "*/*"
    HTTPreq.SetRequestHeader "cache-control", "no-cache"
    HTTPreq.SetRequestHeader "postman-token", "52edacc2-5d59-41d4-beec-5f5448e5f92e"
    HTTPreq.SetRequestHeader "host", "api-dev.dhl.com"
    HTTPreq.SetRequestHeader "accept-encoding", "gzip, deflate, br"
    HTTPreq.SetRequestHeader "connection", "keep-alive"
    HTTPreq.SetRequestHeader "content-length", "109"
    
    strBody = "{""grant_type"": ""client_credentials"", ""scope"": ""myapi2"", ""client_id"": ""zzzzzz"", ""client_secret"": ""xxxxxxx""}"
    
    Debug.Print strBody
    HTTPreq.send strBody
    
    Set JSON = JsonConverter.ParseJson(HTTPreq.responseText)
    Debug.Print HTTPreq.responseText
    
    Set HTTPreq = Nothing
    Set JSON = Nothing

End Sub

But unfortunately, here I don't get a 200 OK response. I get this:

{"status":400,"title":"Bad Request","detail":"One or more required form parameters are missing."}

Since it works in the Postman app, it must be something VBA related that I am not formatting correctly. Can you please help me which part is incorrect in VBA?

Thanks!
Tomas

[Welshgasman]

What does the output of Debug.Print strBody show?
Why the double double quotes?, when the header detail has only single double quotes?

Perhaps have a look here and here

[Thomasso]

What does the output of Debug.Print strBody show?
Why the double double quotes?, when the header detail has only single double quotes?

Perhaps have a look here

Debug.Print strBody shows this:

{"grant_type": "client_credentials", "scope": "myapi2", "client_id": "yyyyy", "client_secret": "zzzzz"}

Double quotes because that gives single quotes instead of string end in VBA. I am assuming at this point that body needs to be included with the Send method as a single string, whereas header requests must be included separately - hence the difference between header/body.

You sent a link to Postman testing. That is exactly what I am doing though, as can be seen in the imgur pictures in the initial post :-)

[Welshgasman]

See the second link and the first link from that.

Is content-length actually meant to be a string?

I do notice that link uses a different HttpReq object?

[Thomasso]

Which link do you mean? Are you aware that every person can potentially get different search results on Google?

I tried to remove the quotes from content-length parameter, that did not change anything.

What do you mean by "link uses different object"?

[Edgar]

Your postman request shows there are 8 hidden headers.
The message you got is informing you that the body is wrong.
It's quite likely that a lot of those headers aren't even necessary.
You probably only need content-type.
And your content type is a JSON string, not url encoded.

Try to send this as the body instead, modify with your credentials.
grant_type=client_credentials&scope=myapi2&client_ id=zzzzzz&client_secret=xxxxxxx

[Thomasso]

Your postman request shows there are 8 hidden headers.
The message you got is informing you that the body is wrong.
It's quite likely that a lot of those headers aren't even necessary.
You probably only need content-type.
And your content type is a JSON string, not url encoded.

Try to send this as the body instead, modify with your credentials.
grant_type=client_credentials&scope=myapi2&client_ id=zzzzzz&client_secret=xxxxxxx

Yes, I just found the same thing as you wrote this. The problem was that the integration uses x-www-form-urlencoded, which requires your proposed syntax. Now I successfully got the token, thank you!