'''<summary>
    '''Sendet POP3 Befehl zum Server.
    '''</summary>
    '''<param name="Command">POP3 Befehl</param>
    Private Sub Send(ByVal Command As String)
 
        Dim data As [Byte]() = System.Text.Encoding.ASCII.GetBytes(Command & _
          vbCrLf)
        Me.POP3Stream.Write(data, 0, data.Length)
 
    End Sub
 
    '''<summary>
    '''Empfängt Antwort auf Send-Befehl vom Server.
    '''</summary>
    Private Function GetResponse() As String
 
        Dim SR As New IO.StreamReader(Me.POP3Stream)
        Dim SBuilder As New System.Text.StringBuilder
        Do While SR.Peek > -1
            SBuilder.Append(SR.ReadLine + vbCr)
        Loop
        Return SBuilder.ToString
 
    End Function
 
    '''<summary>
    '''Prüft ob die erhalten Antwort von GetResponse gültig ist.
    '''</summary>
    '''<param name="Response">Antort von GetResponse</param>
    Private Sub CheckResponse(ByVal Response As String)
 
        If Not String.Compare(Response.Substring(0, 3), Commands.ServerConfirm, _
          False, Globalization.CultureInfo.CurrentCulture) = 0 Then
            Me.Client.Close()
            Me.Connected = False
            Throw New ApplicationException("Response " + Response + " not" & _
              "expected.")
        End If
 
    End Sub
 
    '''<summary>
    '''Gibt eine List(of POP3Message) der verfügbaren Nachrichten zurück.
    '''</summary>
    Public Function GetMessageList() As List(Of MessageList)
 
        If Me.Connected = False Then
            Throw New InvalidOperationException("Not connected!")
        End If
        Dim Pop3l As New List(Of MessageList)
        Me.Send(Commands.List)
        Dim Response() As String = Me.GetResponse.Split(vbCrLf)
        CheckResponse(Response(0))
 
        For i As Integer = 1 To Response.Length - 3
            Dim POP3m As New MessageList
            POP3m.ID = i
            POP3m.Size = Convert.ToInt64(Response(i).Split(" ")(1))
            Pop3l.Add(POP3m)
        Next
 
        Return Pop3l
 
    End Function
 
    '''<summary>
    '''Nachricht mit angebener Nummer vom Server lesen
    '''</summary>
    '''<param name="MessageID">MessageID</param>
    Public Function GetMessage(ByVal MessageID As Integer) As String
 
        If Me.Connected = False Then
            Throw New InvalidOperationException("Not connected!")
        End If
        Me.Send(Commands.GetMessage & MessageID)
        Me.CheckResponse(Me.GetResponse)
        Dim Response As String = Me.GetResponse
        Return Response
 
    End Function
 
End Class