Imports System.Net
Imports System.Net.Http
Imports System.Threading.Tasks

Public Class AS2MDNSender
    Private uri As Uri
    Private from As String
    Private [to] As String
    Private messageId As String

    Sub New(ByVal uri As Uri, ByVal from As String, ByVal [to] As String, ByVal messageId As String)
        Me.uri = uri
        Me.from = from
        Me.to = [to]
        Me.messageId = messageId
    End Sub

    Sub send()
        Threading.ThreadPool.QueueUserWorkItem(AddressOf SendMDN)
    End Sub

    Private Function SendMDN() As HttpResponseMessage
        Threading.Thread.Sleep(10000)
        Using httpClient As New HttpClient
            Using content = New MultipartContent("report")
                'content.Headers.TryAddWithoutValidation("Content-Type", "report-type=disposition-notification")
                content.Headers.Add("Message-Id", String.Format("<AS2_{0}@{1}>", Date.Now.ToString("yyyyMMddHHmmssfff"), "247"))
                content.Headers.Add("AS2-Version", "1.1")
                content.Headers.Add("AS2-From", from)
                content.Headers.Add("AS2-To", [to])

                Dim contentText = "Receipt text"
                content.Add(New StringContent(contentText))

                Dim contentHeaders = "Disposition: automatic-action/MDN-sent-automatically; processed" & vbNewLine &
                    "Final-Recipient: rfc822; " & [to] & vbNewLine &
                    "Original-Recipient: rfc822; " & [to] & vbNewLine &
                    "Original-Message-ID: " & messageId & vbNewLine
                content.Add(New StringContent(contentHeaders, Encoding.UTF8, "message/disposition-notification"))

                Return httpClient.PostAsync(uri, content).Result
            End Using
        End Using
    End Function
End Class