An HTTP file server (130 lines of code) in VB.Net - vb.net

Question

Two weeks ago I found a very interesting article: "A HTTP file server in 130 lines of code". I translated the original code in Visual basic (I use Visual Basic Net 2005 Express).
Imports System
Imports System.IO
Imports System.Net
Imports System.Text
Imports System.Web
Public Class HttpFileServer
Implements IDisposable
Public rootPath As String
Private Const bufferSize As Integer = 1024 * 512
'512KB
Private ReadOnly http As HttpListener
Public Sub New(ByVal rootPath As String)
Me.rootPath = rootPath
http = New HttpListener()
http.Prefixes.Add("http://localhost:80/")
http.Start()
http.BeginGetContext(requestWait, Nothing)
End Sub
Public Sub Dispose() Implements System.IDisposable.Dispose
http.[Stop]()
End Sub
Private Sub requestWait(ByVal ar As IAsyncResult)
If Not http.IsListening Then
Return
End If
Dim c = http.EndGetContext(ar)
http.BeginGetContext(requestWait, Nothing)
Dim url = tuneUrl(c.Request.RawUrl)
Dim fullPath = IIf(String.IsNullOrEmpty(url), rootPath, Path.Combine(rootPath, url))
If Directory.Exists(fullPath) Then
returnDirContents(c, fullPath)
ElseIf File.Exists(fullPath) Then
returnFile(c, fullPath)
Else
return404(c)
End If
End Sub
Private Sub returnDirContents(ByVal context As HttpListenerContext, ByVal dirPath As String)
context.Response.ContentType = "text/html"
context.Response.ContentEncoding = Encoding.UTF8
Using sw = New StreamWriter(context.Response.OutputStream)
sw.WriteLine("html")
sw.WriteLine("head meta http-equiv=""Content-Type"" content=""text/html; charset=utf-8""/head")
sw.WriteLine("body ul")
Dim dirs = Directory.GetDirectories(dirPath)
For Each d As Object In dirs
Dim link = d.Replace(rootPath, "").Replace("\"c, "/"c)
sw.WriteLine("<li><DIR> a href=""" + link + """ " + Path.GetFileName(d) + "/a /li ")
Next
Dim files = Directory.GetFiles(dirPath)
For Each f As Object In files
Dim link = f.Replace(rootPath, "").Replace("\"c, "/"c)
sw.WriteLine(" li <a href=""" + link + """ " + Path.GetFileName(f) + " /a /li ")
Next
sw.WriteLine(" /ul /body /html ")
End Using
context.Response.OutputStream.Close()
End Sub
Private Shared Sub returnFile(ByVal context As HttpListenerContext, ByVal filePath As String)
context.Response.ContentType = getcontentType(Path.GetExtension(filePath))
Dim buffer = New Byte(bufferSize - 1) {}
Using fs = File.OpenRead(filePath)
context.Response.ContentLength64 = fs.Length
Dim read As Integer
While (InlineAssignHelper(read, fs.Read(buffer, 0, buffer.Length))) > 0
context.Response.OutputStream.Write(buffer, 0, read)
End While
End Using
context.Response.OutputStream.Close()
End Sub
Private Shared Sub return404(ByVal context As HttpListenerContext)
context.Response.StatusCode = 404
context.Response.Close()
End Sub
Private Shared Function tuneUrl(ByVal url As String) As String
url = url.Replace("/"c, "\"c)
url = HttpUtility.UrlDecode(url, Encoding.UTF8)
url = url.Substring(1)
Return url
End Function
Private Shared Function getcontentType(ByVal extension As String) As String
Select Case extension
Case ".avi"
Return "video/x-msvideo"
Case ".css"
Return "text/css"
Case ".doc"
Return "application/msword"
Case ".gif"
Return "image/gif"
Case ".htm", ".html"
Return "text/html"
Case ".jpg", ".jpeg"
Return "image/jpeg"
Case ".js"
Return "application/x-javascript"
Case ".mp3"
Return "audio/mpeg"
Case ".png"
Return "image/png"
Case ".pdf"
Return "application/pdf"
Case ".ppt"
Return "application/vnd.ms-powerpoint"
Case ".zip"
Return "application/zip"
Case ".txt"
Return "text/plain"
Case Else
Return "application/octet-stream"
End Select
End Function
Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, ByVal value As T) As T
target = value
Return value
End Function
End Class
But I got errors:
Error 1 Argument not specified for parameter 'ar' of 'Private Sub requestWait(ar As System.IAsyncResult)'. line 19
Error 2 Argument not specified for parameter 'ar' of 'Private Sub requestWait(ar As System.IAsyncResult)'. line 31
Both errors refer to the expression http.BeginGetContext(requestWait, Nothing). But I don't know how to handle this.

Answer 1

To compile your code change the lines
http.BeginGetContext(requestWait, Nothing)
to
http.BeginGetContext(AddressOf requestWait, Nothing)
You can have a look at AddressOf Operator and this question.