Imports System.Net.Sockets
Imports System.Net
Imports System.Text
Imports System.Threading
 
Public Class Form1
 
    Private udpServer As UdpClient
    Private udpClient As UdpClient
    Private netIP As IPEndPoint
    Private threadCallback As AsyncCallback
    Private udpPort As Integer = 514
    Delegate Sub DelegateWriteRtf(t As String)
 
 
    Sub StartServer()
 
        threadCallback = New AsyncCallback(AddressOf dataReceive)
        netIP = New IPEndPoint(IPAddress.Any, udpPort)
 
        udpServer = New UdpClient(netIP)
 
        udpServer.BeginReceive(threadCallback, "") ' Starte asyncrones Empfangen
        writeLog("Server listen on " & netIP.Address.ToString & ":" & _
          netIP.Port.ToString)
 
    End Sub
 
    Sub dataReceive(asyncResult As IAsyncResult)
 
        Dim byteData() As Byte = udpServer.EndReceive(asyncResult, netIP)
        Dim strData = Encoding.ASCII.GetString(byteData)
        writeLog(strData)
        If asyncResult.IsCompleted Then 'Wieder auf empfang gehen
            udpServer.BeginReceive(threadCallback, Nothing)
        End If
 
    End Sub
End Class

    Sub StoppServer()
        udpServer.Close()
        udpServer = Nothing
    End Sub