Option Strict On

Imports System.Runtime.InteropServices
Imports System.Text
Imports System.Threading

' This class provides all the necessary support for communicating
'   with the Comm Port (otherwise known as the Serial Port, or 
'   RS232 port).
Public Class Rs232
    ' Declare the necessary class variables, and their initial values.		
    Private mhRS As Integer = -1   ' Handle to Com Port									
    Private miPort As Integer = 1   ' Default is COM1	
    Private miTimeout As Integer = 70   ' Timeout in ms
    Private miBaudRate As Integer = 9600
    Private meParity As DataParity = 0
    Private meStopBit As DataStopBit = 0
    Private miDataBit As Integer = 8
    Private miBufferSize As Integer = 512   ' Buffers size default to 512 bytes
    Private mabtRxBuf As Byte()   ' Receive buffer	
    Private meMode As Mode  ' Class working mode	
    Private mbWaitOnRead As Boolean
    Private mbWaitOnWrite As Boolean
    Private mbWriteErr As Boolean
    Private muOverlapped As OVERLAPPED
    Private muOverlappedW As OVERLAPPED
    Private muOverlappedE As OVERLAPPED
    Private mabtTmpTxBuf As Byte()  ' Temporary buffer used by Async Tx
    Private moThreadTx As Thread
    Private moThreadRx As Thread
    Private miTmpBytes2Read As Integer
    Private meMask As EventMasks

#Region "Enums"

    ' This enumeration provides Data Parity values.
    Public Enum DataParity
        Parity_None = 0
        Pariti_Odd
        Parity_Even
        Parity_Mark
    End Enum

    ' This enumeration provides Data Stop Bit values.
    '   It is set to begin with a one, so that the enumeration values
    '   match the actual values.
    Public Enum DataStopBit
        StopBit_1 = 1
        StopBit_2
    End Enum

    ' This enumeration contains values used to purge the various buffers.
    Private Enum PurgeBuffers
        RXAbort = &H2
        RXClear = &H8
        TxAbort = &H1
        TxClear = &H4
    End Enum

    ' This enumeration provides values for the lines sent to the Comm Port
    Private Enum Lines
        SetRts = 3
        ClearRts = 4
        SetDtr = 5
        ClearDtr = 6
        ResetDev = 7   '	 Reset device if possible
        SetBreak = 8   '	 Set the device break line.
        ClearBreak = 9   '	 Clear the device break line.
    End Enum
    ' This enumeration provides values for the Modem Status, since
    '   we'll be communicating primarily with a modem.
    ' Note that the Flags() attribute is set to allow for a bitwise
    '   combination of values.
    <Flags()> Public Enum ModemStatusBits
        ClearToSendOn = &H10
        DataSetReadyOn = &H20
        RingIndicatorOn = &H40
        CarrierDetect = &H80
    End Enum

    ' This enumeration provides values for the Working mode
    Public Enum Mode
        NonOverlapped
        Overlapped
    End Enum

    ' This enumeration provides values for the Comm Masks used.
    ' Note that the Flags() attribute is set to allow for a bitwise
    '   combination of values.
    <Flags()> Public Enum EventMasks
        RxChar = &H1
        RXFlag = &H2
        TxBufferEmpty = &H4
        ClearToSend = &H8
        DataSetReady = &H10
        ReceiveLine = &H20
        Break = &H40
        StatusError = &H80
        Ring = &H100
    End Enum
#End Region

#Region "Structures"
    ' This is the DCB structure used by the calls to the Windows API.
    <StructLayout(LayoutKind.Sequential, Pack:=1)> Private Structure DCB
        Public DCBlength As Integer
        Public BaudRate As Integer
        Public Bits1 As Integer
        Public wReserved As Int16
        Public XonLim As Int16
        Public XoffLim As Int16
        Public ByteSize As Byte
        Public Parity As Byte
        Public StopBits As Byte
        Public XonChar As Byte
        Public XoffChar As Byte
        Public ErrorChar As Byte
        Public EofChar As Byte
        Public EvtChar As Byte
        Public wReserved2 As Int16
    End Structure

    ' This is the CommTimeOuts structure used by the calls to the Windows API.
    <StructLayout(LayoutKind.Sequential, Pack:=1)> Private Structure COMMTIMEOUTS
        Public ReadIntervalTimeout As Integer
        Public ReadTotalTimeoutMultiplier As Integer
        Public ReadTotalTimeoutConstant As Integer
        Public WriteTotalTimeoutMultiplier As Integer
        Public WriteTotalTimeoutConstant As Integer
    End Structure

    ' This is the CommConfig structure used by the calls to the Windows API.
    <StructLayout(LayoutKind.Sequential, Pack:=1)> Private Structure COMMCONFIG
        Public dwSize As Integer
        Public wVersion As Int16
        Public wReserved As Int16
        Public dcbx As DCB
        Public dwProviderSubType As Integer
        Public dwProviderOffset As Integer
        Public dwProviderSize As Integer
        Public wcProviderData As Byte
    End Structure

    ' This is the OverLapped structure used by the calls to the Windows API.
    <StructLayout(LayoutKind.Sequential, Pack:=1)> Public Structure OVERLAPPED
        Public Internal As Integer
        Public InternalHigh As Integer
        Public Offset As Integer
        Public OffsetHigh As Integer
        Public hEvent As Integer
    End Structure
#End Region

#Region "Exceptions"

    ' This class defines a customized channel exception. This exception is
    '   raised when a NACK is raised.
    Public Class CIOChannelException : Inherits ApplicationException
        Sub New(ByVal Message As String)
            MyBase.New(Message)
        End Sub
        Sub New(ByVal Message As String, ByVal InnerException As Exception)
            MyBase.New(Message, InnerException)
        End Sub
    End Class

    ' This class defines a customized timeout exception.
    Public Class IOTimeoutException : Inherits CIOChannelException
        Sub New(ByVal Message As String)
            MyBase.New(Message)
        End Sub
        Sub New(ByVal Message As String, ByVal InnerException As Exception)
            MyBase.New(Message, InnerException)
        End Sub
    End Class

#End Region

#Region "Events"
    ' These events allow the program using this class to react to Comm Port
    '   events.
    Public Event DataReceived(ByVal Source As Rs232, ByVal DataBuffer() As Byte)
    Public Event TxCompleted(ByVal Source As Rs232)
    Public Event CommEvent(ByVal Source As Rs232, ByVal Mask As EventMasks)
#End Region

#Region "Constants"
    ' These constants are used to make the code clearer.
    Private Const PURGE_RXABORT As Integer = &H2
    Private Const PURGE_RXCLEAR As Integer = &H8
    Private Const PURGE_TXABORT As Integer = &H1
    Private Const PURGE_TXCLEAR As Integer = &H4
    Private Const GENERIC_READ As Integer = &H80000000
    Private Const GENERIC_WRITE As Integer = &H40000000
    Private Const OPEN_EXISTING As Integer = 3
    Private Const INVALID_HANDLE_VALUE As Integer = -1
    Private Const IO_BUFFER_SIZE As Integer = 1024
    Private Const FILE_FLAG_OVERLAPPED As Integer = &H40000000
    Private Const ERROR_IO_PENDING As Integer = 997
    Private Const WAIT_OBJECT_0 As Integer = 0
    Private Const ERROR_IO_INCOMPLETE As Integer = 996
    Private Const WAIT_TIMEOUT As Integer = &H102&
    Private Const INFINITE As Integer = &HFFFFFFFF


#End Region

#Region "Properties"

    ' This property gets or sets the BaudRate
    Public Property BaudRate() As Integer
        Get
            Return miBaudRate
        End Get
        Set(ByVal Value As Integer)
            miBaudRate = Value
        End Set
    End Property

    ' This property gets or sets the BufferSize
    Public Property BufferSize() As Integer
        Get
            Return miBufferSize
        End Get
        Set(ByVal Value As Integer)
            miBufferSize = Value
        End Set
    End Property

    ' This property gets or sets the DataBit.
    Public Property DataBit() As Integer
        Get
            Return miDataBit
        End Get
        Set(ByVal Value As Integer)
            miDataBit = Value
        End Set
    End Property

    ' This write-only property sets or resets the DTR line.
    Public WriteOnly Property Dtr() As Boolean
        Set(ByVal Value As Boolean)
            If Not mhRS = -1 Then
                If Value Then
                    EscapeCommFunction(mhRS, Lines.SetDtr)
                Else
                    EscapeCommFunction(mhRS, Lines.ClearDtr)
                End If
            End If
        End Set
    End Property

    ' This read-only property returns an array of bytes that represents
    '   the input coming into the Comm Port.
    Overridable ReadOnly Property InputStream() As Byte()
        Get
            Return mabtRxBuf
        End Get
    End Property

    ' This read-only property returns a string that represents
    '   the data coming into to the Comm Port.
    Overridable ReadOnly Property InputStreamString() As String
        Get
            Dim oEncoder As New System.Text.ASCIIEncoding()
            Return oEncoder.GetString(Me.InputStream)
        End Get
    End Property

    ' This property returns the open status of the Comm Port.
    ReadOnly Property IsOpen() As Boolean
        Get
            Return CBool(mhRS <> -1)
        End Get
    End Property

    ' This read-only property returns the status of the modem.
    Public ReadOnly Property ModemStatus() As ModemStatusBits
        Get
            If mhRS = -1 Then
                Throw New ApplicationException("Please initialize and open " + _
                    "port before using this method")
            Else
                ' Retrieve modem status