Imports System
Imports System.io
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Threading
Imports System.Math
Imports Microsoft.VisualBasic.ControlChars
 
Public Structure UserDaten
   Dim code As String
   Dim UserID As String
End Structure
 
 
Module Serverapplikation
 
   Public anzUser As Int32 = 2
   Public arrAnzahlUser() As UserDaten
   Public bestaetigung(10) As Byte
 
   Sub Main()
 
      Dim anfrage(10), bestaetigung(10) As Byte
      ReDim arrAnzahlUser(anzUser - 1)
      Dim ID1, ID2 As UserDaten
 
      'User 1
      ID1.code = "1111"
      ID1.UserID = "01"
      'User 2
      ID2.code = "2222"
      ID2.UserID = "02"
      arrAnzahlUser(0) = ID1
      arrAnzahlUser(1) = ID2
 
      Dim IpHostInfo As IPHostEntry = Dns.Resolve(Dns.GetHostName())
      Dim serverEndPoint As New IPEndPoint(IpHostInfo.AddressList(0), 3333)
      'Serverdaten:
      Console.WriteLine("Port des Servers: {0}", serverEndPoint.Port.ToString())
      Console.WriteLine("IP des Servers: {0}" & CrLf, _
        serverEndPoint.Address.ToString())
 
      While (1)
         Dim server As New Socket(AddressFamily.InterNetwork, _
                                       SocketType.Dgram, ProtocolType.Udp)
         'Das Binden des ServerSockets ist für die ReceiveFrom-Funktion 
         ' vorausgesetzt.
         server.Bind(serverEndPoint)
 
         'Kreiert einen IpEndPoint, um die IP und den Port des Clients zu 
         ' speichern.
         Dim clientEndPoint As New IPEndPoint(IPAddress.Any, 0)
 
         Try
            'Empfangen des Codes
            Console.WriteLine("Warte auf Code-Anfrage des Client...")
            server.ReceiveFrom(anfrage, clientEndPoint)
            Console.WriteLine("Habe Anfrage des Client erhalten: {0}" & CrLf, _
              Encoding.ASCII.GetString(anfrage))
            Dim zcode As String = Encoding.ASCII.GetString(anfrage).TrimEnd( _
            NullChar)
            Dim bla As String = vergleich(zcode, arrAnzahlUser)
            Dim strCode() As Byte = Encoding.ASCII.GetBytes(bla)
 
            'Clientdaten:
            Console.WriteLine("Port des Client: {0}", _
              clientEndPoint.Port.ToString())
            Console.WriteLine("IP des Client: {0}" & CrLf, _
            clientEndPoint.Address.ToString())
 
            'Senden des Codes
            server.SendTo(strCode, clientEndPoint)
            Console.WriteLine("Code an Client gesendet: {0}" & CrLf, bla)
 
            'Bestätigung abwarten
            Console.WriteLine("Warte auf Bestätigung des Client...")
            server.ReceiveFrom(bestaetigung, clientEndPoint)
            Console.WriteLine("Habe Bestätigung erhalten: {0}" & CrLf, _
              Encoding.ASCII.GetString(bestaetigung).TrimEnd(NullChar))
 
         Catch e As Exception
            Console.WriteLine(e.ToString())
         Finally
            server.Close()
         End Try
      End While
      Console.ReadLine()
   End Sub
End Module
 
Module codeVergleich
   Public Function vergleich(ByVal zcode, ByVal arrAnzahlUser) As String
      Dim i As Integer
      For i = 0 To UBound(arrAnzahlUser)
         If zcode Like arrAnzahlUser(i).userID Then
            Return arrAnzahlUser(i).code
         End If
      Next
      Return -1
   End Function
End Module