Private Shared Listen_Server As Socket   
Private Shared Connection_Server As Socket    
Private Shared receivebuffer(511) As Byte    
Private Shared allDone As New ManualResetEvent(False)     
Private Shared Sub StartServer()        
If Form1.tb_localport.Text <> "" Then           
 'StatusBar1.Text = "Waiting For connection"            
MsgBox("Waiting For connection")       
     Form1.bt_listen.Enabled = False         
   Form1.bt_disconnect.Enabled = True    
        Listen_Server = New Socket(AddressFamily.InterNetwork, _            _
          SocketType.Stream, ProtocolType.Tcp)    
        Dim localEP As New IPEndPoint(IPAddress.Any, Val( _
        Form1.tb_localport.Text))       
     Try              
  Listen_Server.Bind(localEP) 'IP-Adresse und Port binden     
       Catch ex As Exception      
          'statusbar1.Text = "ERROR On binding socket"          
      MsgBox("ERROR On binding socket")  
          End Try            
Try             
   Listen_Server.Listen(100) 'Listen-Server starten  
          Catch ex As Exception          
      closeconnections()             
   'statusbar1.Text = "ERROR On Start Listening"      
          MsgBox("ERROR On Start Listening")     
       End Try    
        While True          
      allDone.Reset()          
      Listen_Server.BeginAccept(AddressOf callback_accept, Listen_Server)           
     allDone.WaitOne()        
    End While       
 End If   
 End Sub   
  Public Shared Sub callback_accept(ByVal ar As IAsyncResult)     
   'statusbar1.Text = "connected"   
     MsgBox("connected")     
   Form1.bt_senddata.Enabled = True        
Application.DoEvents()      
  Try           
 Connection_Server = Listen_Server.EndAccept(ar)     
  Connection_Server.BeginReceive(receivebuffer, 0, 512, SocketFlags.None, _     _
           New AsyncCallback(AddressOf callback_readdata), Connection_Server)     
       allDone.Set()        
Catch ex As Exception 
           'statusbar1.Text = "no connection"      
      MsgBox("no connection")     
   End Try    
End Sub