Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.IO
Imports System.Threading
Imports System.Text.Encoding
 
Public Class Network
    Public Class Server
 
        Public Sub StartListener()
            Dim ListenerThread As New Thread(AddressOf StartListening)
            ListenerThread.IsBackground = True
            ListenerThread.Start()
        End Sub
 
        Public allDone As New ManualResetEvent(False)
 
        Private Sub StartListening()
            Try
                Dim server As New Socket(AddressFamily.InterNetwork, _
                  SocketType.Stream, ProtocolType.Tcp)
                server.Bind(New IPEndPoint(IPAddress.Parse("127.0.0.1"), 5555))
                server.Listen(5)
 
                While True
                    allDone.Reset()
                    server.BeginAccept(AddressOf AcceptCallBack, server)
                    allDone.WaitOne()
                End While
            Catch e As Exception
                MessageBox.Show(e.Message)
            End Try
        End Sub
 
        Private Sub AcceptCallBack(ByVal ar As IAsyncResult)
            Dim Listener As Socket = CType(ar.AsyncState, Socket)
            Dim handler As Socket = Listener.EndAccept(ar)
 
            Dim state As New StateObject
            state.workSocket = handler
            Array.Clear(state.buffer, 0, state.buffersize)
            handler.BeginReceive(state.buffer, 0, StateObject.buffersize, _
              SocketFlags.None, AddressOf ReceiveCallBack, state)
 
        End Sub
 
        Private Sub ReceiveCallBack(ByVal ar As IAsyncResult)
            Dim state As StateObject = CType(ar.AsyncState, StateObject)
            Dim handler As Socket = state.workSocket
            Dim content As String = String.Empty
            Dim bytesRead% = handler.EndReceive(ar)
 
            content = ASCII.GetString(state.buffer)
 
            If bytesRead > 0 Then
                handler.BeginReceive(state.buffer, 0, state.buffersize, _
                  SocketFlags.None, AddressOf ReceiveCallBack, state)
                Dim msgwin As New MsgWindow(content)
                msgwin.Show()
            End If
 
            Array.Clear(state.buffer, 0, state.buffersize)
        End Sub
    End Class
 
    Public Class StateObject
        Public workSocket As Socket = Nothing
        Public Const buffersize As Integer = 1023
        Public buffer(buffersize) As Byte
    End Class
End Class