Imports System
Imports System.Text
Imports System.Drawing
Imports System.IO.Ports
Imports System.Windows.Forms
Imports System.Threading


Public Class Form1

    Dim testo As String
    Public trd As Thread
    Delegate Sub SetTextCallback(ByVal [text] As String)

   Private Sub ConfigurazioneSerialeToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ConfigurazioneSerialeToolStripMenuItem.Click
        SerialPort1.Close()
        'trd.Suspend()
        Form2.ShowDialog()
        ' trd.Resume()
    End Sub


    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Form2.ShowDialog()
        'trd = New Thread(AddressOf ThreadProcUnsafe)
        'trd.IsBackground = True
        'trd.Start()
    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If SerialPort1.IsOpen = False Then
            SerialPort1.Open()
        End If

        SerialPort1.Write(TextBox2.Text)
        TextBox1.ForeColor = Color.Blue
        TextBox1.Text &= "Msg Inviato:" & TextBox2.Text & vbCrLf
        TextBox2.Text = ""
    End Sub


    Private Sub ThreadProcUnsafe()

        Do
            testo = ""

            Try

                SerialPort1.ReadTimeout = 500

                Do
                    Dim Incoming As String = SerialPort1.ReadLine()
                    If Incoming Is Nothing Then
                        Exit Do
                    Else
                        testo &= Incoming & vbCrLf
                    End If

                Loop


            Catch ex As TimeoutException
                'testo = "Nessuno dato ricevuto"
            End Try

            Thread.Sleep(1000)

            If testo <> "" Then
                Me.SetText(testo)
            End If
        Loop
    End Sub


    Private Sub Form1_Unload(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.FormClosed
        'trd.Suspend()
        SerialPort1.Close()
    End Sub


    Private Sub SetText(ByVal [text] As String)

       If Me.TextBox1.InvokeRequired Then
            Dim d As New SetTextCallback(AddressOf SetText)
            Me.Invoke(d, New Object() {[text]})
        Else
            Me.TextBox1.Text = [text]
        End If
    End Sub


    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        testo = ""
        System.Threading.Thread.Sleep(300)
        testo = (SerialPort1.ReadExisting)

        If testo <> "" Then
            TextBox1.ForeColor = Color.Red
            TextBox1.Text &= "Msg Ricevuto:" & testo & vbCrLf
        End If

    End Sub

End Class