Option Strict On
Public Class HttpDownloadEX
    Public Event DownloadFinished()
    Public Event DownloadProgress(ByVal progress As String)
    Public Event DownloadError(reason  as string)
    Private firstpacket As Boolean = True
    Private kb As Integer = 1024
    Private StartTick As Long = 0
    Private DownloadedBytes As Long = 0
    Private Abort As Boolean
    Private Structure STATEOBJECT
        Dim sock As Net.Sockets.Socket
        Const bufSize% = 32768
        Dim buf() As Byte
        Dim fStream As IO.FileStream
        Dim resuming As Boolean
        Dim fSize&
        Dim remoteFileName$
        Dim port%
        Dim rHOST$
        Dim connected As Boolean
        Dim fName$
    End Structure
    Public Sub New(ByVal host As String, ByVal remoteFileName As String, ByVal _
      localFile As String, Optional ByVal port As Integer = 80)
        startdownload(host, remoteFileName, localFile, port)
    End Sub
    Private Sub startdownload(ByVal host As String, ByVal remoteFileName As _
      String, ByVal localFile As String, Optional ByVal port As Integer = 80)
        Dim fSize&
        Dim sObject As New STATEOBJECT
        sObject.fName = localFile
        If IO.File.Exists(localFile) Then sObject.resuming = True
        If IO.File.Exists(localFile) Then fSize = New IO.FileInfo( _
          localFile).Length
        ReDim sObject.buf(sObject.bufSize - 1)
        sObject.fSize = fSize
        sObject.fStream = Nothing
        sObject.port = port
        sObject.remoteFileName = remoteFileName
        sObject.rHOST = host
        sObject.sock = New Net.Sockets.Socket( _
          Net.Sockets.AddressFamily.InterNetwork, _
          Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)
        Net.Dns.BeginResolve(host, AddressOf resolvecallback, sObject)
    End Sub
    Protected Sub resolvecallback(ByVal ar As IAsyncResult)
        Dim sobject As STATEOBJECT = CType(ar.AsyncState, STATEOBJECT)
        If Not ar.IsCompleted Then
            Net.Dns.BeginResolve(sobject.rHOST, AddressOf resolvecallback, _
              sobject)
            Exit Sub
        End If
        Dim rhe As Net.IPHostEntry = Net.Dns.EndResolve(ar)
        Dim ipe As New Net.IPEndPoint(rhe.AddressList(0), sobject.port)
        sobject.sock.BeginConnect(ipe, AddressOf connectcallback, sobject)
    End Sub
    Protected Sub connectcallback(ByVal ar As IAsyncResult)
        Dim sobject As STATEOBJECT = CType(ar.AsyncState, STATEOBJECT)
        Try
            sobject.sock.EndConnect(ar)
            sobject.connected = True
            ' hier sind wir nun connected und sollten erstmal unseren request 
            ' senden und natürlich die response empfangen !
            sobject.buf = System.Text.Encoding.Default.GetBytes(HttpRequest( _
              sobject))
            Dim bSent As Integer = sobject.sock.Send(sobject.buf, 0, _
            sobject.buf.Length, Net.Sockets.SocketFlags.None)
            ReDim sobject.buf(sobject.bufSize - 1)
            sobject.sock.BeginReceive(sobject.buf, 0, sobject.bufSize, _
              Net.Sockets.SocketFlags.None, AddressOf readcallback, sobject)
        Catch e As System.Net.Sockets.SocketException
            If e.ErrorCode = 10065 Then
                ' connection timed out ...
                RaiseEvent DownloadError("Connection timed out ...")
                Abort = True
            ElseIf e.ErrorCode = 10061 Then
                ' connection refused ...
                RaiseEvent DownloadError("connection refused ...")
                Abort = True
            Else
                RaiseEvent DownloadError("Connection error ...")
                Abort = True
            End If
        End Try
    End Sub
    ' empfängt daten vom webserver !
    Protected Sub readcallback(ByVal ar As IAsyncResult)
        If Not Abort Then
            Dim sobject As STATEOBJECT = CType(ar.AsyncState, STATEOBJECT)
            Dim bRead% = sobject.sock.EndReceive(ar)
            If bRead = 0 Then
                ' download finished
                RaiseEvent DownloadFinished()
                If Not Nothing Is sobject.sock Then
                    sobject.sock.Close()
                End If
                sobject = Nothing
                Exit Sub
            End If
            processData(sobject, bRead)
            ReDim sobject.buf(sobject.bufSize - 1)
            sobject.sock.BeginReceive(sobject.buf, 0, sobject.bufSize, _
              Net.Sockets.SocketFlags.None, AddressOf readcallback, sobject)
        End If
    End Sub
 
fortsetzung folgt