I have a form with a text box, a thread start button, and a seperate thread.
This is a TCP listener (server) example I took out of a book. See the code
below. In the loop below, look at the two lines I have marked with a comment
of ??????? If I don't write to the text box, I have a fast response.  The
value "returnedData" is written to the console in a timely manner.  However,
if I try to write to the textbox, tbStatus, the response slows to about 1
time per second.  Is there some problem with writing to a textbox from within
a seperate thread?? Can somesone suggest a solution.

Hamil.

   Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnStart.Click
       btnStart.Enabled = False
       btnStop.Enabled = True
       Dim tr As New Thread(AddressOf ListenToClients)
       tr.Start()
   End Sub

   Sub ListenToClients()
       'localhostAddress =  IPAddress.Loopback
       localhostAddress = IPAddress.Parse("192.168.1.5")
       port = CInt(txtPort.Text)
       tcpList = New TcpListener(localhostAddress, port)
       tcpList.Start()
       listening = True
       Do While listening
           Do While tcpList.Pending = False And listening = True
               Thread.Sleep(10)
           Loop
           If Not listening Then Exit Do
           Dim tcpCli As New TcpClient
           tcpCli = tcpList.AcceptTcpClient()
           ns = tcpCli.GetStream
           sr = New StreamReader(ns)
           sw = New StreamWriter(ns)
           tbStatus.Text = "connected"
           Do While listening = True
               Thread.Sleep(10)
               receivedData = sr.ReadLine
               If receivedData <> Nothing Then
                   returnedData = ProcessInput(receivedData)

                   Console.WriteLine(returnedData) '???????????
                   tbStatus.Text = returnedData  '???????????????

                   sw.WriteLine(returnedData)
                   sw.Flush()
               End If
           Loop
           sr.Close()
           sw.Close()
           ns.Close()
           tcpCli.Close()
           tbStatus.Text = "closed"
       Loop
       tcpList.Stop()
   End Sub