VB.NET Help creating login function for custom launcher!

I'm currently creating my own Launcher in VB.NET and everything is basically done except some small things as custom JVM arguments.

I'm currently stuck at creating some sort of login function I have read a bit here:
http://wiki.vg/Authentication

I have one idea that might work, and that is to have some sort of PHP script that fetches the accesstoken.
I do not have much experience in VB.NET I did this as an challenge to learn more.

This is how it looks at the moment:
https://gyazo.com/af17968c14658ce4ea433bfeb993204a

Do anyone have any idea on how I should make my login function and if someone would like to help out / bring new ideas that would be great!

 

I managed to get it fixed if someone else needs login function for VB.net here you have it:

Code (Text):

    Private ACCESS_TOKEN As String
    Public Function GetAccessToken() As String
        Return ACCESS_TOKEN
    End Function
    Public Sub ObtainAccessToken(username As String, password As String)
        Dim UUID As String = Guid.NewGuid.ToString()
        Dim httpWebRequest = DirectCast(WebRequest.Create("https://authserver.mojang.com/authenticate"), HttpWebRequest)
        httpWebRequest.ContentType = "application/json"
        httpWebRequest.Method = "POST"

        Using streamWriter = New StreamWriter(httpWebRequest.GetRequestStream())
            Dim json As String = (Convert.ToString((Convert.ToString("{""agent"":{""name"":""Minecraft"",""version"":1},""username"":""") & username) + """,""password"":""") & password) + """,""clientToken"":" & ControlChars.Quote & UUID & ControlChars.Quote & "}"

            streamWriter.Write(json)
            streamWriter.Flush()
            streamWriter.Close()

            Dim httpResponse = DirectCast(httpWebRequest.GetResponse(), HttpWebResponse)
            Using streamReader = New StreamReader(httpResponse.GetResponseStream())
                Dim result = streamReader.ReadToEnd()
                ACCESS_TOKEN = result
                MessageBox.Show(result)
            End Using
        End Using
    End Sub