Using vb.net, how to send POST request with post data and save the binary response to a file?

I am trying to write a console script that makes a POST request to a web server with post data and saves the response from the server to a file.  The server response is a compressed tar archive.  I'm able to make the request using weblclient upload data, but I cannot figure out a way to save the binary response to a variable and eventually to a file.

I am using vb.net framework 1.1.

Here is a snippet of my code so far:

    ' Download a single binary file from a server and save it to a local folder
    Public Sub DownloadAndSaveFile(ByVal Url As String, ByVal Filename As String, ByVal User As String, ByVal Pass As String, ByVal Debug As Integer)

        ' The post data template
        Dim PostdataTemplate As String = _
        "handler=SOME_URLENCODED_DATA"

        Dim PostdataArray As Byte() = Encoding.ASCII.GetBytes(Postdata)

        ' Create a new NetworkCredential object
        Dim NetworkCredential As New NetworkCredential(User, Pass)

        Try
            ' Create a new WebClient instance
            Dim myWebClient As New WebClient

            ' Set Preauthenticate property to true
            'myWebClient.PreAuthenticate = True

            ' Associate the NetworkCrbedential object with the 'WebRequest' object
            myWebClient.Credentials = NetworkCredential

            ' Add required HTTP headers to request
            myWebClient.Headers.Add("Accept", "*/*")
            myWebClient.Headers.Add("Content-Type", "application/x-www-form-urlencoded")

            ' UploadData method implicitly sets HTTP POST as the request method
            Dim responseArray As Byte() = myWebClient.UploadData(Url, PostdataArray)
            ' The response array as byte generates an exception!

        Catch Ex As Exception
            WriteLine("Error: " & Ex.Message)

        End Try
    End Sub

I get an exception when saving the response as a byte:

Error: The underlying connection was closed: The server committed an HTTP protocol violation.

If I change the server to respond with ascii text, the response is correctly saved.  I think the issue is that I'm trying to save binary data to a variable that only handles text.

Can someone provide an example of how to send a POST request with parameters and then save the binary file that the server responds with to a local file?

Thanks!
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