Imports System.IO.Ports

Public Class Form1
    Delegate Sub SetTextCallback(ByVal [text] As String)

    Private Sub UpdateCOMPortList()
        Dim s As String
        Dim i As Integer
        Dim foundDifference As Boolean

        i = 0
        foundDifference = False

        If lstCOMPorts.Items.Count = SerialPort.GetPortNames().Length Then
            For Each s In SerialPort.GetPortNames()
                If lstCOMPorts.Items(i).Equals(s) = False Then
                    foundDifference = True
                End If
                i = i + 1
            Next s
        Else
            foundDifference = True
        End If
        If foundDifference = False Then
            Exit Sub
        End If
        lstCOMPorts.Items.Clear()
        For Each s In SerialPort.GetPortNames()
            lstCOMPorts.Items.Add(s)
        Next s
        lstCOMPorts.SelectedIndex = 0
    End Sub

    Private Sub UpdateCOMPortList2()
        Dim s As String
        Dim i As Integer
        Dim foundDifference As Boolean

        i = 0
        foundDifference = False

        If lstCOMPorts2.Items.Count = SerialPort.GetPortNames().Length Then
            For Each s In SerialPort.GetPortNames()
                If lstCOMPorts2.Items(i).Equals(s) = False Then
                    foundDifference = True
                End If
                i = i + 1
            Next s
        Else
            foundDifference = True
        End If
        If foundDifference = False Then
            Exit Sub
        End If
        lstCOMPorts2.Items.Clear()
        For Each s In SerialPort.GetPortNames()
            lstCOMPorts2.Items.Add(s)
        Next s
        lstCOMPorts2.SelectedIndex = 0
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        UpdateCOMPortList()
        UpdateCOMPortList2()
    End Sub

    Private Sub btnConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click
        Try
            SerialPort1.PortName = lstCOMPorts.Items(lstCOMPorts.SelectedIndex).ToString()
            SerialPort1.Open()

            btnConnect.Enabled = False
            lstCOMPorts.Enabled = False
            btnClose.Enabled = True
            txtDataReceived.Clear()
            txtDataReceived.AppendText("Connected." + vbCrLf)
        Catch ex As Exception
            btnClose_Click(Me, e)

        End Try
    End Sub

    Private Sub btnConnect2_Click(sender As System.Object, e As System.EventArgs) Handles btnConnect2.Click
        Try
            SerialPort2.PortName = lstCOMPorts2.Items(lstCOMPorts2.SelectedIndex).ToString()
            SerialPort2.Open()

            btnConnect2.Enabled = False
            lstCOMPorts2.Enabled = False
            btnClose2.Enabled = True
            txtDataReceived2.Clear()
            txtDataReceived2.AppendText("Connected." + vbCrLf)
        Catch ex As Exception
            btnClose2_Click(Me, e)

        End Try

    End Sub

    Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click
        btnClose.Enabled = False
        btnConnect.Enabled = True
        lstCOMPorts.Enabled = True
        Try
            SerialPort1.DiscardInBuffer()
            SerialPort1.DiscardOutBuffer()
            SerialPort1.Close()
        Catch ex As Exception
        End Try
    End Sub
    Private Sub btnClose2_Click(sender As System.Object, e As System.EventArgs) Handles btnClose2.Click
        btnClose2.Enabled = False
        btnConnect2.Enabled = True
        lstCOMPorts2.Enabled = True
        Try
            SerialPort2.DiscardInBuffer()
            SerialPort2.DiscardOutBuffer()
            SerialPort2.Close()
        Catch ex As Exception
        End Try

    End Sub
 
    Private Sub SerialPort1_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        Try
            SetText(SerialPort1.ReadExisting())
        Catch ex As Exception
            btnClose_Click(Me, e)
        End Try

    End Sub
    Private Sub SerialPort2_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort2.DataReceived
        Try
            SetText2(SerialPort2.ReadExisting())
        Catch ex As Exception
            btnClose2_Click(Me, e)
        End Try

    End Sub

    Private Sub SetText(ByVal [text] As String)
        If txtDataReceived.InvokeRequired Then
            Dim d As New SetTextCallback(AddressOf SetText)
            Invoke(d, New Object() {[text]})
        Else
            txtDataReceived.AppendText(text)
        End If
    End Sub

    Private Sub SetText2(ByVal [text] As String)
        If txtDataReceived2.InvokeRequired Then
            Dim d As New SetTextCallback(AddressOf SetText2)
            Invoke(d, New Object() {[text]})
        Else
            txtDataReceived2.AppendText(text)
        End If
    End Sub

    Private Sub btnSendData_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSendData.Click
        Try
            SerialPort1.Write(txtData.Text)
        Catch ex As Exception
            btnClose_Click(Me, e)
        End Try
    End Sub

    Private Sub btnSendData2_Click(sender As System.Object, e As System.EventArgs) Handles btnSendData2.Click
        Try
            SerialPort2.Write(txtData2.Text)
        Catch ex As Exception
            btnClose2_Click(Me, e)
        End Try

    End Sub
End Class