Conexion por modem

Hola, un modem no tiene nada de sofisticado, lo tenes que usar como un puerto
serie, pero con la diferencia que tenes que utilizar un protocolo muy simple
(AT), por ejemplo, para realizar una llamada tenes que mandar :

"atdt" + NumeroDeTelefono

Para que conteste automaticamente creo que es:

"ats0=" + Cantidad_De_Rings_para_contestar

bueno.. y muchisimos comandos mas para configurar cosas como el volumen del
modem, contestacion manual, etc... para utilizar el puerto serie, podes
utilizar el control MSCOMM32.OCX (viene con visual studio 6.0) o utilizar la
forma .NET que utiliza algunas APIs... yo tengo un codigo que me baje que es
vb.net, con el cual hice otro proyecto y lo use, el codigo es este: (CONTINUA
EN EL OTRO POST PORQUE EL MAXIMO ES 30000 CARACTERES!!)



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
Dim lpModemStatus As Integer
If Not GetCommModemStatus(mhRS, lpModemStatus) Then
Throw New ApplicationException("Unable to get modem
status")
Else
Return CType(lpModemStatus, ModemStatusBits)
End If
End If
End Get
End Property

' This property gets or sets the Parity
Public Property Parity() As DataParity
Get
Return meParity
End Get
Set(ByVal Value As DataParity)
meParity = Value
End Set
End Property

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

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

' This property gets or sets the StopBit
Public Property StopBit() As DataStopBit
Get
Return meStopBit
End Get
Set(ByVal Value As DataStopBit)
meStopBit = Value
End Set
End Property

' This property gets or sets the Timeout
Public Overridable Property Timeout() As Integer
Get
Return miTimeout
End Get
Set(ByVal Value As Integer)
miTimeout = CInt(IIf(Value = 0, 500, Value))
' If Port is open updates it on the fly
pSetTimeout()
End Set
End Property

' This property gets or sets the working mode to overlapped
' or non-overlapped.
Public Property WorkingMode() As Mode
Get
Return meMode
End Get
Set(ByVal Value As Mode)
meMode = Value
End Set
End Property

#End Region


#Region "Win32API"
' The following functions are the required Win32 functions needed to
' make communication with the Comm Port possible.

<DllImport("kernel32.dll")> Private Shared Function BuildCommDCB( _
ByVal lpDef As String, ByRef lpDCB As DCB) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function ClearCommError( _
ByVal hFile As Integer, ByVal lpErrors As Integer, _
ByVal l As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function CloseHandle( _
ByVal hObject As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function CreateEvent( _
ByVal lpEventAttributes As Integer, ByVal bManualReset As Integer, _
ByVal bInitialState As Integer, _
<MarshalAs(UnmanagedType.LPStr)> ByVal lpName As String) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function CreateFile( _
<MarshalAs(UnmanagedType.LPStr)> ByVal lpFileName As String, _
ByVal dwDesiredAccess As Integer, ByVal dwShareMode As Integer, _
ByVal lpSecurityAttributes As Integer, _
ByVal dwCreationDisposition As Integer, _
ByVal dwFlagsAndAttributes As Integer, _
ByVal hTemplateFile As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function EscapeCommFunction( _
ByVal hFile As Integer, ByVal ifunc As Long) As Boolean
End Function

<DllImport("kernel32.dll")> Private Shared Function FormatMessage( _
ByVal dwFlags As Integer, ByVal lpSource As Integer, _
ByVal dwMessageId As Integer, ByVal dwLanguageId As Integer, _
<MarshalAs(UnmanagedType.LPStr)> ByVal lpBuffer As String, _
ByVal nSize As Integer, ByVal Arguments As Integer) As Integer
End Function

Private Declare Function FormatMessage Lib "kernel32" Alias _
"FormatMessageA" (ByVal dwFlags As Integer, ByVal lpSource As Integer, _
ByVal dwMessageId As Integer, ByVal dwLanguageId As Integer, _
ByVal lpBuffer As StringBuilder, ByVal nSize As Integer, _
ByVal Arguments As Integer) As Integer

<DllImport("kernel32.dll")> Public Shared Function GetCommModemStatus( _
ByVal hFile As Integer, ByRef lpModemStatus As Integer) As Boolean
End Function

<DllImport("kernel32.dll")> Private Shared Function GetCommState( _
ByVal hCommDev As Integer, ByRef lpDCB As DCB) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetCommTimeouts( _
ByVal hFile As Integer, ByRef lpCommTimeouts As COMMTIMEOUTS) As
Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetLastError() As
Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function GetOverlappedResult( _
ByVal hFile As Integer, ByRef lpOverlapped As OVERLAPPED, _
ByRef lpNumberOfBytesTransferred As Integer, _
ByVal bWait As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function PurgeComm( _
ByVal hFile As Integer, ByVal dwFlags As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function ReadFile( _
ByVal hFile As Integer, ByVal Buffer As Byte(), _
ByVal nNumberOfBytesToRead As Integer, _
ByRef lpNumberOfBytesRead As Integer, _
ByRef lpOverlapped As OVERLAPPED) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommTimeouts( _
ByVal hFile As Integer, ByRef lpCommTimeouts As COMMTIMEOUTS) As
Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommState( _
ByVal hCommDev As Integer, ByRef lpDCB As DCB) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetupComm( _
ByVal hFile As Integer, ByVal dwInQueue As Integer, _
ByVal dwOutQueue As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function SetCommMask( _
ByVal hFile As Integer, ByVal lpEvtMask As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function WaitCommEvent( _
ByVal hFile As Integer, ByRef Mask As EventMasks, _
ByRef lpOverlap As OVERLAPPED) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function WaitForSingleObject( _
ByVal hHandle As Integer, ByVal dwMilliseconds As Integer) As Integer
End Function

<DllImport("kernel32.dll")> Private Shared Function WriteFile( _
ByVal hFile As Integer, ByVal Buffer As Byte(), _
ByVal nNumberOfBytesToWrite As Integer, _
ByRef lpNumberOfBytesWritten As Integer, _
ByRef lpOverlapped As OVERLAPPED) As Integer
End Function

#End Region

#Region "Methods"

' This subroutine invokes a thread to perform an asynchronous read.
' This routine should not be called directly, but is used
' by the class.
Public Sub _R()
Dim iRet As Integer = Read(miTmpBytes2Read)
End Sub

' This subroutine invokes a thread to perform an asynchronous write.
' This routine should not be called directly, but is used
' by the class.
Public Sub _W()
Write(mabtTmpTxBuf)
End Sub

' This subroutine uses another thread to read from the Comm Port. It
' raises RxCompleted when done. It reads an integer.
Public Overloads Sub AsyncRead(ByVal Bytes2Read As Integer)
If meMode <> Mode.Overlapped Then Throw New ApplicationException( _
"Async Methods allowed only when WorkingMode=Overlapped")
miTmpBytes2Read = Bytes2Read
moThreadTx = New Thread(AddressOf _R)
moThreadTx.Start()
End Sub

' This subroutine uses another thread to write to the Comm Port. It
' raises TxCompleted when done. It writes an array of bytes.
Public Overloads Sub AsyncWrite(ByVal Buffer() As Byte)
If meMode <> Mode.Overlapped Then Throw New ApplicationException( _
"Async Methods allowed only when WorkingMode=Overlapped")
If mbWaitOnWrite = True Then Throw New ApplicationException( _
"Unable to send message because of pending transmission.")
mabtTmpTxBuf = Buffer
moThreadTx = New Thread(AddressOf _W)
moThreadTx.Start()
End Sub

' This subroutine uses another thread to write to the Comm Port. It
' raises TxCompleted when done. It writes a string.
Public Overloads Sub AsyncWrite(ByVal Buffer As String)
Dim oEncoder As New System.Text.ASCIIEncoding()
Dim aByte() As Byte = oEncoder.GetBytes(Buffer)
Me.AsyncWrite(aByte)
End Sub

' This function takes the ModemStatusBits and returns a boolean value
' signifying whether the Modem is active.
Public Function CheckLineStatus(ByVal Line As ModemStatusBits) As Boolean
Return Convert.ToBoolean(ModemStatus And Line)
End Function

' This subroutine clears the input buffer.
Public Sub ClearInputBuffer()
If Not mhRS = -1 Then
PurgeComm(mhRS, PURGE_RXCLEAR)
End If
End Sub

' This subroutine closes the Comm Port.
Public Sub Close()
If mhRS <> -1 Then
CloseHandle(mhRS)
mhRS = -1
End If
End Sub

' This subroutine opens and initializes the Comm Port
Public Overloads Sub Open()
' Get Dcb block,Update with current data
Dim uDcb As DCB, iRc As Integer
' Set working mode
Dim iMode As Integer = Convert.ToInt32(IIf(meMode = Mode.Overlapped, _
FILE_FLAG_OVERLAPPED, 0))
' Initializes Com Port
If miPort > 0 Then
Try
' Creates a COM Port stream handle
mhRS = CreateFile("COM" & miPort.ToString, _
GENERIC_READ Or GENERIC_WRITE, 0, 0, _
OPEN_EXISTING, iMode, 0)
If mhRS <> -1 Then
' Clear all comunication errors
Dim lpErrCode As Integer
iRc = ClearCommError(mhRS, lpErrCode, 0&)
' Clears I/O buffers
iRc = PurgeComm(mhRS, PurgeBuffers.RXClear Or _
PurgeBuffers.TxClear)
' Gets COM Settings
iRc = GetCommState(mhRS, uDcb)
' Updates COM Settings
Dim sParity As String = "NOEM"
sParity = sParity.Substring(meParity, 1)
' Set DCB State
Dim sDCBState As String = String.Format( _
"baud={0} parity={1} data={2} stop={3}", _
miBaudRate, sParity, miDataBit, CInt(meStopBit))
iRc = BuildCommDCB(sDCBState, uDcb)
iRc = SetCommState(mhRS, uDcb)
If iRc = 0 Then
Dim sErrTxt As String = pErr2Text(GetLastError())
Throw New CIOChannelException( _
"Unable to set COM state0" & sErrTxt)
End If
' Setup Buffers (Rx,Tx)
iRc = SetupComm(mhRS, miBufferSize, miBufferSize)
' Set Timeouts
pSetTimeout()
Else
' Raise Initialization problems
Throw New CIOChannelException( _
"Unable to open COM" & miPort.ToString)
End If
Catch Ex As Exception
' Generica error
Throw New CIOChannelException(Ex.Message, Ex)
End Try
Else
' Port not defined, cannot open
Throw New ApplicationException("COM Port not defined, " + _
"use Port property to set it before invoking InitPort")
End If
End Sub

' This subroutine opens and initializes the Comm Port (overloaded
' to support parameters).
Public Overloads Sub Open(ByVal Port As Integer, _
ByVal BaudRate As Integer, ByVal DataBit As Integer, _
ByVal Parity As DataParity, ByVal StopBit As DataStopBit, _
ByVal BufferSize As Integer)

Me.Port = Port
Me.BaudRate = BaudRate
Me.DataBit = DataBit
Me.Parity = Parity
Me.StopBit = StopBit
Me.BufferSize = BufferSize
Open()
End Sub

(CONTINUACION DEL CODIGO)


' This function translates an API error code to text.
Private Function pErr2Text(ByVal lCode As Integer) As String
Dim sRtrnCode As New StringBuilder(256)
Dim lRet As Integer

lRet = FormatMessage(&H1000, 0, lCode, 0, sRtrnCode, 256, 0)
If lRet > 0 Then
Return sRtrnCode.ToString
Else
Return "Error not found."
End If

End Function

' This subroutine handles overlapped reads.
Private Sub pHandleOverlappedRead(ByVal Bytes2Read As Integer)
Dim iReadChars, iRc, iRes, iLastErr As Integer
muOverlapped.hEvent = CreateEvent(Nothing, 1, 0, Nothing)
If muOverlapped.hEvent = 0 Then
' Can't create event
Throw New ApplicationException( _
"Error creating event for overlapped read.")
Else
' Ovellaped reading
If mbWaitOnRead = False Then
ReDim mabtRxBuf(Bytes2Read - 1)
iRc = ReadFile(mhRS, mabtRxBuf, Bytes2Read, _
iReadChars, muOverlapped)
If iRc = 0 Then
iLastErr = GetLastError()
If iLastErr <> ERROR_IO_PENDING Then
Throw New ArgumentException("Overlapped Read Error:
" & _
pErr2Text(iLastErr))
Else
' Set Flag
mbWaitOnRead = True
End If
Else
' Read completed successfully
RaiseEvent DataReceived(Me, mabtRxBuf)
End If
End If
End If
' Wait for operation to be completed
If mbWaitOnRead Then
iRes = WaitForSingleObject(muOverlapped.hEvent, miTimeout)
Select Case iRes
Case WAIT_OBJECT_0
' Object signaled,operation completed
If GetOverlappedResult(mhRS, muOverlapped, _
iReadChars, 0) = 0 Then

' Operation error
iLastErr = GetLastError()
If iLastErr = ERROR_IO_INCOMPLETE Then
Throw New ApplicationException( _
"Read operation incomplete")
Else
Throw New ApplicationException( _
"Read operation error " & iLastErr.ToString)
End If
Else
' Operation completed
RaiseEvent DataReceived(Me, mabtRxBuf)
mbWaitOnRead = False
End If
Case WAIT_TIMEOUT
Throw New IOTimeoutException("Timeout error")
Case Else
Throw New ApplicationException("Overlapped read error")
End Select
End If
End Sub

' This subroutine handles overlapped writes.
Private Function pHandleOverlappedWrite(ByVal Buffer() As Byte) As Boolean
Dim iBytesWritten, iRc, iLastErr, iRes As Integer, bErr As Boolean
muOverlappedW.hEvent = CreateEvent(Nothing, 1, 0, Nothing)
If muOverlappedW.hEvent = 0 Then
' Can't create event
Throw New ApplicationException( _
"Error creating event for overlapped write.")
Else
' Overllaped write
PurgeComm(mhRS, PURGE_RXCLEAR Or PURGE_TXCLEAR)
mbWaitOnRead = True
iRc = WriteFile(mhRS, Buffer, Buffer.Length, _
iBytesWritten, muOverlappedW)
If iRc = 0 Then
iLastErr = GetLastError()
If iLastErr <> ERROR_IO_PENDING Then
Throw New ArgumentException("Overlapped Read Error: " & _
pErr2Text(iLastErr))
Else
' Write is pending
iRes = WaitForSingleObject(muOverlappedW.hEvent, INFINITE)
Select Case iRes
Case WAIT_OBJECT_0
' Object signaled,operation completed
If GetOverlappedResult(mhRS, muOverlappedW, _
iBytesWritten, 0) = 0 Then

bErr = True
Else
' Notifies Async tx completion,stops thread
mbWaitOnRead = False
RaiseEvent TxCompleted(Me)
End If
End Select
End If
Else
' Wait operation completed immediatly
bErr = False
End If
End If
CloseHandle(muOverlappedW.hEvent)
Return bErr
End Function

' This subroutine sets the Comm Port timeouts.
Private Sub pSetTimeout()
Dim uCtm As COMMTIMEOUTS
' Set ComTimeout
If mhRS = -1 Then
Exit Sub
Else
' Changes setup on the fly
With uCtm
.ReadIntervalTimeout = 0
.ReadTotalTimeoutMultiplier = 0
.ReadTotalTimeoutConstant = miTimeout
.WriteTotalTimeoutMultiplier = 10
.WriteTotalTimeoutConstant = 100
End With
SetCommTimeouts(mhRS, uCtm)
End If
End Sub

' This function returns an integer specifying the number of bytes
' read from the Comm Port. It accepts a parameter specifying the number
' of desired bytes to read.
Public Function Read(ByVal Bytes2Read As Integer) As Integer
Dim iReadChars, iRc As Integer

' If Bytes2Read not specified uses Buffersize
If Bytes2Read = 0 Then Bytes2Read = miBufferSize
If mhRS = -1 Then
Throw New ApplicationException( _
"Please initialize and open port before using this method")
Else
' Get bytes from port
Try
' Purge buffers
'PurgeComm(mhRS, PURGE_RXCLEAR Or PURGE_TXCLEAR)
' Creates an event for overlapped operations
If meMode = Mode.Overlapped Then
pHandleOverlappedRead(Bytes2Read)
Else
' Non overlapped mode
ReDim mabtRxBuf(Bytes2Read - 1)
iRc = ReadFile(mhRS, mabtRxBuf, Bytes2Read, iReadChars,
Nothing)
If iRc = 0 Then
' Read Error
Throw New ApplicationException( _
"ReadFile error " & iRc.ToString)
Else
' Handles timeout or returns input chars
If iReadChars < Bytes2Read Then
Throw New IOTimeoutException("Timeout error")
Else
mbWaitOnRead = True
Return (iReadChars)
End If
End If
End If
Catch Ex As Exception
' Others generic erroes
Throw New ApplicationException("Read Error: " & Ex.Message,
Ex)
End Try
End If
End Function

' This subroutine writes the passed array of bytes to the
' Comm Port to be written.
Public Overloads Sub Write(ByVal Buffer As Byte())
Dim iBytesWritten, iRc As Integer

If mhRS = -1 Then
Throw New ApplicationException( _
"Please initialize and open port before using this method")
Else
' Transmit data to COM Port
Try
If meMode = Mode.Overlapped Then
' Overlapped write
If pHandleOverlappedWrite(Buffer) Then
Throw New ApplicationException( _
"Error in overllapped write")
End If
Else
' Clears IO buffers
PurgeComm(mhRS, PURGE_RXCLEAR Or PURGE_TXCLEAR)
iRc = WriteFile(mhRS, Buffer, Buffer.Length, _
iBytesWritten, Nothing)
If iRc = 0 Then
Throw New ApplicationException( _
"Write Error - Bytes Written " & _
iBytesWritten.ToString & " of " & _
Buffer.Length.ToString)
End If
End If
Catch Ex As Exception
Throw
End Try
End If
End Sub

' This subroutine writes the passed string to the
' Comm Port to be written.
Public Overloads Sub Write(ByVal Buffer As String)
Dim oEncoder As New System.Text.ASCIIEncoding()
Dim aByte() As Byte = oEncoder.GetBytes(Buffer)
Me.Write(aByte)
End Sub

#End Region

End Class