system.net.webclient post error 400

Question

I have this HTTP post that with curl under w10 work fine

curl https://auth.sinch.com/oauth2/token -d grant_type=client_credentials -u username:password

This require a basic authentication and return a token

I need to implement this under vb.net (frameworks 4.5.2)

I've tyred with system.net.webclient (I've already used for other similar) but I always get error 400.

This is the code:

Dim myCreds As NetworkCredential = New NetworkCredential("Myusername", "Mypassword")

    Dim url As String = "https://auth.sinch.com/oauth2/token"  

    Using client As New WebClient 'POST

        client.Credentials = myCreds

        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

        client.Headers.Add("Content-Type", "application/x-www-form-urlencoded")

           Dim result As String = client.UploadString(url, "POST", "grant_type=client_credentials")

    End Using
```Any Idea where is the error? 

Thank you

Alessandro

Answer 1

Hi @alessandro belli ,

Try sending the credentials in the request body.

        Dim url As String = "https://auth.sinch.com/oauth2/token"
        Dim credentials As String = Convert.ToBase64String(Encoding.ASCII.GetBytes("Myusername:Mypassword"))
        Dim postData As String = "grant_type=client_credentials"

        Using client As New WebClient()
            client.Headers(HttpRequestHeader.Authorization) = "Basic " & credentials
            client.Headers(HttpRequestHeader.ContentType) = "application/x-www-form-urlencoded"
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

            Dim responseBytes As Byte() = client.UploadData(url, "POST", Encoding.ASCII.GetBytes(postData))
            Dim responseBody As String = Encoding.ASCII.GetString(responseBytes)

            Console.WriteLine(responseBody)
        End Using

Best Regards.

Jiachen Li

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