Imports System.Net.Sockets
Imports System.Text
 
Public Class Form1
 
    Private SimpleServer As TcpListener
    Private Client As New TcpClient
    Private Stream As NetworkStream
    Dim returnValue As IAsyncResult
    Dim bytes() As Byte
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
        SimpleServer = New TcpListener(System.Net.IPAddress.Parse(0), 12345)
 
        SimpleServer.Start()
 
        SimpleServer.BeginAcceptTcpClient(AddressOf OnConnect, New Object)
 
    End Sub
 
    Private Sub OnConnect(ByVal ar As System.IAsyncResult)
        Client = SimpleServer.EndAcceptTcpClient(ar)
        Stream = Client.GetStream
 
        ReDim bytes(Client.ReceiveBufferSize)
        Stream.BeginRead(bytes, 0, CInt(Client.ReceiveBufferSize), AddressOf _
          onGetData, New Object)
    End Sub
 
    Private Sub onGetData(ByVal ar As System.IAsyncResult)
 
        Dim clientdata As String = Encoding.ASCII.GetString(bytes)
        returnValue = Stream.BeginRead(bytes, 0, CInt( _
          Client.ReceiveBufferSize), AddressOf onGetData, New Object)
        Stream.EndRead(returnValue)
    End Sub
End Class

 Imports System.Net.Sockets
Imports System.Text
 
Public Class Form1
 
    Private SimpleClient As New TcpClient
    Private Stream As NetworkStream
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        SimpleClient.Connect("127.0.0.1", 12345)
        Stream = SimpleClient.GetStream
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
 
        Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes("Is anybody there")
        Stream.Write(sendBytes, 0, sendBytes.Length)
    End Sub
End Class