Public Class Form1
 
    Dim serverstatus As Integer = 0
 
    Dim client As New Socket(AddressFamily.InterNetwork, SocketType.Stream, _
      ProtocolType.IP)
 
    Dim server As New Socket(AddressFamily.InterNetwork, SocketType.Stream, _
      ProtocolType.IP)
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
        CheckForIllegalCrossThreadCalls = False
 
        ServStatLB.Text = serverstatus
 
        Dim iphost As IPHostEntry = Dns.Resolve(Dns.GetHostName())
 
        IPAdressesCB.Items.AddRange(iphost.AddressList)
 
        IPAdressesCB.Items.Add("127.0.0.1")
 
        IPAdressesCB.SelectedIndex = 0
 
        StartServer.PerformClick()
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles StartServer.Click
 
        Dim ServerIP As IPAddress = IPAddress.Parse( _
          IPAdressesCB.SelectedItem.ToString())
 
        Dim LocalEndPoint As New IPEndPoint(ServerIP, 26000)
 
        server.Bind(LocalEndPoint)
 
        server.Listen(2)
 
        serverstatus = 1
 
        ServStatLB.Text = serverstatus
 
        StatLB.Text = "Server listening on: " & CType(server.LocalEndPoint, _
          IPEndPoint).Address.ToString() & ":" & CType(server.LocalEndPoint, _
          IPEndPoint).Port.ToString()
 
        AcceptConnectionsBGW.RunWorkerAsync()
 
    End Sub
 
    Private Sub AcceptConnectionsBGW_DoWork(ByVal sender As System.Object, _
      ByVal e As System.ComponentModel.DoWorkEventArgs) Handles _
      AcceptConnectionsBGW.DoWork
 
        Do While serverstatus = 1
 
            client = server.Accept()
 
            Dim port As Int32 = CType(client.RemoteEndPoint, IPEndPoint).Port
 
            Dim tcpip As String = CType(client.RemoteEndPoint, _
              IPEndPoint).Address.ToString()
 
            ConnectedClientsLB.Items.Add(tcpip & ":" & port)
 
            Dim bytes(client.ReceiveBufferSize) As Byte
 
            Dim str As String = Encoding.ASCII.GetString(bytes, 0, _
              client.Receive(bytes))
 
            MsgTB.Text += str & Environment.NewLine
 
            If MessageThreadBGW.IsBusy = False Then
 
                MessageThreadBGW.RunWorkerAsync()
 
            End If
 
        Loop
 
    End Sub
 
    Private Sub StopServer_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles StopServer.Click
 
        server.Close()
 
        serverstatus = 0
 
        ServStatLB.Text = serverstatus
 
        StatLB.Text = "Server gestoppt"
 
    End Sub
 
    Private Sub MessageThreadBGW_DoWork(ByVal sender As System.Object, ByVal e _
      As System.ComponentModel.DoWorkEventArgs) Handles MessageThreadBGW.DoWork
 
        Do While serverstatus = 1
 
            Dim bytes(client.ReceiveBufferSize) As Byte
 
            Dim str As String = Encoding.ASCII.GetString(bytes, 0, _
              client.Receive(bytes))
 
            MsgTB.Text += str & Environment.NewLine
 
        Loop
 
    End Sub
 
End Class