InternetModem Source Code

'***************************************************

'* This code belongs to Terry R. Olsen

'* You are free to use this code in whole or

'* in part for your own programs. But you may

'* not use this code in any way to create

'* the same type of program for public release.

'* My Email: tolsen64@hotmail.com

'***************************************************

Imports System.Net

Imports System.Net.Sockets

Imports System.Windows.forms

Imports System.Text.ASCIIEncoding

Imports System.IO

Imports System.IO.Ports

Module Module1

#Region "Telnet Commands"

' Telnet main commands - list copied from somewhere on the net - thank you to them

Const TN_IAC As Int32 = 255 ' Interpret as command escape sequence, Prefix to all telnet commands. 1, 2 or sometimes more commands normally follow this character

Const TN_DONT As Int32 = 254 ' You are not to use this option

Const TN_DO As Int32 = 253 ' Please, you use this option

Const TN_WONT As Int32 = 252 ' I won't use option

Const TN_WILL As Int32 = 251 ' I will use option

Const TN_SB As Int32 = 250 ' Subnegotiate, X number of commands follow

Const TN_GA As Int32 = 249 ' Go ahead

Const TN_EL As Int32 = 248 ' Erase line

Const TN_EC As Int32 = 247 ' Erase character

Const TN_AYT As Int32 = 246 ' Are you there

Const TN_AO As Int32 = 245 ' Abort output

Const TN_IP As Int32 = 244 ' Interrupt process

Const TN_BRK As Int32 = 243 ' Break

Const TN_DM As Int32 = 242 ' Data mark

Const TN_NOP As Int32 = 241 ' No operation.

Const TN_SE As Int32 = 240 ' End of subnegotiation, from above

Const TN_EOR As Int32 = 239 ' End of record

Const TN_ABORT As Int32 = 238 ' About process

Const TN_SUSP As Int32 = 237 ' Suspend process

Const TO_EOF As Int32 = 236 ' End of file

' Telnet (option) mainly return commands from above

Const TN_BIN As Int32 = 0 ' Binary transmission

Const TN_ECHO As Int32 = 1 ' Echo

Const TN_RECN As Int32 = 2 ' Reconnection

Const TN_SUPP As Int32 = 3 ' Suppress go ahead

Const TN_APRX As Int32 = 4 ' Approx message size negotiation

Const TN_STAT As Int32 = 5 ' Status

Const TN_TIM As Int32 = 6 ' Timing mark

Const TN_REM As Int32 = 7 ' Remote controlled trans/echo

Const TN_OLW As Int32 = 8 ' Output line width

Const TN_OPS As Int32 = 9 ' Output page size

Const TN_OCRD As Int32 = 10 ' Out carriage-return disposition

Const TN_OHT As Int32 = 11 ' Output horizontal tabstops

Const TN_OHTD As Int32 = 12 ' Out horizontal tab disposition

Const TN_OFD As Int32 = 13 ' Output formfeed disposition

Const TN_OVT As Int32 = 14 ' Output vertical tabstops

Const TN_OVTD As Int32 = 15 ' Output vertical tab disposition

Const TN_OLD As Int32 = 16 ' Output linefeed disposition

Const TN_EXT As Int32 = 17 ' Extended ascii character set

Const TN_LOGO As Int32 = 18 ' Logout

Const TN_BYTE As Int32 = 19 ' Byte macro

Const TN_DATA As Int32 = 20 ' Data entry terminal

Const TN_SUP As Int32 = 21 ' supdup protocol

Const TN_SUPO As Int32 = 22 ' supdup output

Const TN_SNDL As Int32 = 23 ' Send location

Const TN_TERM As Int32 = 24 ' Terminal type

Const TO_EOR As Int32 = 25 ' End of record

Const TN_TACACS As Int32 = 26 ' Tacacs user identification

Const TN_OM As Int32 = 27 ' Output marking

Const TN_TLN As Int32 = 28 ' Terminal location number

Const TN_3270 As Int32 = 29 ' Telnet 3270 regime

Const TN_X3 As Int32 = 30 ' X.3 PAD

Const TN_NAWS As Int32 = 31 ' Negotiate about window size

Const TN_TS As Int32 = 32 ' Terminal speed

Const TN_RFC As Int32 = 33 ' Remote flow control

Const TN_LINE As Int32 = 34 ' Linemode

Const TN_XDL As Int32 = 35 ' X display location

Const TN_ENVIR As Int32 = 36 ' Telnet environment option

Const TN_AUTH As Int32 = 37 ' Telnet authentication option

Const TN_NENVIR As Int32 = 39 ' Telnet environment option

Const TN_EXTOP As Int32 = 25 ' Extended-options-list

#End Region

'Serial Port Stuff

Dim WithEvents Ser As New SerialPort

'Telnet Stuff

Dim LineSize As Integer

Dim TcpPort As Integer = 23

Dim TcpSvr As Socket 'TCP Listener Socket, listens for incoming calls

Dim TcpClt As Socket 'TCP Client Socket, handles incoming calls

Dim TcpMsg As Socket 'Tells Clients that we're busy right now...

'Send & Receive Buffers

Dim RcvBuf() As Byte 'In from TCP/Out to Serial

Dim XmtBuf() As Byte 'In from Serial/Out to TCP

Dim SerByt As Integer 'Bytes to read from serial port

Dim Throttle As Integer 'Some slower terminals may need to slow it down

'BBS not available message

Dim msg() As Byte = ASCII.GetBytes("The line is busy. Please try again later.")

'Stopwatch for measuring +++ Guard Time

Dim swGuardTimer As New System.Timers.Timer

'Application variables

Dim logFile As String

Dim iniFile As String

Dim keepLog As Boolean = False

Dim ver As String = "6.7.29.1"

'Modem Emulator Stuff

Enum ModemEcho

EchoOff = 0

EchoOn = 1

End Enum

Enum ModemResultCodeFormat

Numeric = 0

Text = 1

End Enum

Enum ModemResultCodes

Enabled = 0

Disabled = 1

End Enum

Enum ModemRingMode

SendRing = 0

SendConnect = 1

End Enum

Enum ModemHookState

OnHook = 0

OffHook = 1

End Enum

Const OK As Integer = 0

Const CONNECT As Integer = 1

Const RING As Integer = 2

Const NO_CARRIER As Integer = 3

Const ERR As Integer = 4

Const NO_DIAL_TONE As Integer = 6

Const BUSY As Integer = 7

Const NO_ANSWER As Integer = 8

Dim MdmErr As Integer

Dim MdmErrorCode() As String = {"OK", "CONNECT", "RING", "NO CARRIER", "ERROR", "", "NO DIAL TONE", "BUSY", "NO ANSWER"}

Dim MdmCmdMode As Boolean = True 'Are we in command mode?

Dim MdmCmdStr As String

Dim MdmResultCodeFormat As ModemResultCodeFormat = ModemResultCodeFormat.Numeric

Dim MdmEcho As ModemEcho = ModemEcho.EchoOn

Dim MdmResultCodes As ModemResultCodes = ModemResultCodes.Enabled

Dim MdmRingMode As ModemRingMode = ModemRingMode.SendConnect

Dim MdmHookState As ModemHookState = ModemHookState.OnHook

Dim MdmBaud As String

Sub Main()

'Display Program & Author Information

Console.WriteLine("Internet Modem v" & ver & " by Terry R. Olsen")

Console.WriteLine("Call The BoycoT BBS: telnet://boycot.no-ip.com:9999")

Console.WriteLine("Get the latest version of this program: http://boycot.no-ip.com/InternetModem")

Console.WriteLine("Email: tolsen64@hotmail.com")

Console.WriteLine("=============================================================================")

'Load the INI file. This defines our variables.

WriteStatus("Loading Initialization Data")

Dim tmpPth As String = My.Application.Info.DirectoryPath

If Right(tmpPth, 1) <> "\" Then tmpPth += "\"

iniFile = tmpPth + "InternetModem.ini"

logFile = tmpPth + "InternetModem.log"

Dim r As New StreamReader(iniFile)

Dim tmp() As String

While r.Peek > 0

tmp = Split(r.ReadLine, "=")

Select Case tmp(0)

Case "TcpPort"

TcpPort = CInt(tmp(1))

Case "SerPort"

Ser.PortName = "COM" & Trim(tmp(1))

Case "SerBaud"

Ser.BaudRate = CInt(tmp(1))

MdmBaud = Trim(tmp(1))

Case "SerDataBits"

Ser.DataBits = CInt(tmp(1))

Case "SerParity"

If tmp(1) = "None" Then Ser.Parity = Parity.None

If tmp(1) = "Odd" Then Ser.Parity = Parity.Odd

If tmp(1) = "Even" Then Ser.Parity = Parity.Even

If tmp(1) = "Mark" Then Ser.Parity = Parity.Mark

If tmp(1) = "Space" Then Ser.Parity = Parity.Space

Case "SerStopBits"

If tmp(1) = 1 Then Ser.StopBits = StopBits.One

If tmp(1) = 1.5 Then Ser.StopBits = StopBits.OnePointFive

If tmp(1) = 2 Then Ser.StopBits = StopBits.Two

Case "Handshake"

If tmp(1) = "None" Then Ser.Handshake = Handshake.None

If tmp(1) = "RTS" Then Ser.Handshake = Handshake.RequestToSend

If tmp(1) = "RTS/XonXoff" Then Ser.Handshake = Handshake.RequestToSendXOnXOff

If tmp(1) = "XonXoff" Then Ser.Handshake = Handshake.XOnXOff

Case "RcvBuf"

Ser.WriteBufferSize = CInt(tmp(1))

ReDim RcvBuf(CInt(tmp(1)))

Case "XmtBuf"

Ser.ReadBufferSize = CInt(tmp(1))

ReDim XmtBuf(CInt(tmp(1)))

Case "KeepLog"

keepLog = CBool(tmp(1))

Case "BBSName"

msg = ASCII.GetBytes(tmp(1) & " is currently in use." & vbCrLf & vbCrLf & _

"Please try again soon!" & vbCrLf & vbCrLf & _

"While you're waiting...give The BoycoT BBS a call..." & vbCrLf & _

"telnet://boycot.no-ip.com:9999")

Case "Throttle"

Throttle = CInt(tmp(1))

Case "LineSize"

LineSize = CInt(tmp(1))

End Select

End While

r.Close()

Ser.ReceivedBytesThreshold = 1 'Raise an event for each character received

'Open the serial port

WriteStatus("Opening " & Ser.PortName & "," & Ser.BaudRate & "," & Ser.DataBits & _

"," & Ser.Parity.ToString & "," & Ser.StopBits & "," & Ser.Handshake.ToString)

Try

Ser.Open()

Ser.DtrEnable = True

Ser.RtsEnable = True

Catch ex As Exception

WriteStatus(ex.Message)

WriteStatus("Failed!")

Console.WriteLine("Press ENTER to exit.")

Console.ReadLine()

Exit Sub

End Try

StartTCPServer()

AddHandler swGuardTimer.Elapsed, AddressOf swGuardTimerFired

swGuardTimer.Interval = 1000

'swGuardTimer.Enabled = True

swGuardTimer.Stop()

Application.Run() 'Keeps us running...

End Sub

'====================================================================

'Our TCP Server Routines.

Private Sub StartTCPServer()

Dim addr As IPAddress = IPAddress.Parse("0.0.0.0")

Dim ep As New IPEndPoint(addr, TcpPort)

TcpSvr = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)

TcpSvr.Bind(ep)

TcpSvr.Listen(2)

TcpSvr.BeginAccept(AddressOf AcceptCallback, TcpSvr)

WriteStatus("Listening for calls on TCP Port " & TcpPort)

End Sub

Private Sub AcceptCallback(ByVal ar As IAsyncResult)

Debug.WriteLine(Now.ToLongTimeString & " AcceptCallback")

If TcpClt Is Nothing And MdmHookState = ModemHookState.OnHook Then

Debug.WriteLine("TcpClt=Nothing, MdmHookState=" & MdmHookState.ToString)

TcpClt = TcpSvr.EndAccept(ar)

WriteStatus("Connected to " & CType(TcpClt.RemoteEndPoint, IPEndPoint).ToString)

TcpClt.BeginReceive(RcvBuf, 0, RcvBuf.Length, SocketFlags.None, AddressOf ReceiveCallback, RcvBuf)

MdmCmdMode = False

MdmHookState = ModemHookState.OffHook

ModemError(1)

Else

Debug.WriteLine(Now.ToLongTimeString & " TcpMsg started")

TcpMsg = TcpSvr.EndAccept(ar)

TcpMsg.Send(msg)

WriteStatus("Sent busy message to " & CType(TcpMsg.RemoteEndPoint, IPEndPoint).ToString)

TcpMsg.Shutdown(SocketShutdown.Both)

TcpMsg.Close()

TcpMsg = Nothing

End If

TcpSvr.BeginAccept(AddressOf AcceptCallback, TcpSvr)

WriteStatus("Listening for calls on TCP Port " & TcpPort)

End Sub

Private Sub ReceiveCallback(ByVal ar As IAsyncResult)

RcvBuf = CType(ar.AsyncState, Byte())

Dim numbytes As Int32

Try

numbytes = TcpClt.EndReceive(ar)

Catch

Exit Sub

End Try

If numbytes = 0 Then 'client has disconnected.

Ser.DtrEnable = False

Ser.RtsEnable = False

HangUp(False) 'False = Remote initiated disconnect

MdmHookState = ModemHookState.OnHook

Ser.DtrEnable = True

Ser.RtsEnable = True

ModemError(NO_CARRIER)

Exit Sub

End If

If MdmCmdMode = False Then ProcessIncoming(numbytes)

TcpClt.BeginReceive(RcvBuf, 0, RcvBuf.Length, SocketFlags.None, AddressOf ReceiveCallback, RcvBuf)

End Sub

Sub ProcessIncoming(ByVal numbytes As Int32)

For i As Integer = 0 To numbytes - 1

Select Case RcvBuf(i)

Case TN_IAC

'WriteStatus("Telnet Protocol in use.")

Dim byt(0 To 2) As Byte

byt(0) = TN_IAC

i += 1

Select Case RcvBuf(i)

Case TN_SB

'ToChatWindow(" TN_SB" & vbCrLf)

WriteStatus("TN_SB Received! Subnegotiate Incomplete.")

i += 1

Loop Until RcvBuf(i) = TN_SE Or i = numbytes - 1

Case TN_DO 'Server asking you to do something

'ToChatWindow(" TN_DO " & Str(buffer(i + 1)) & vbCrLf)

i += 1

Select Case RcvBuf(i)

Case TN_NAWS

byt(1) = TN_WILL

byt(2) = RcvBuf(i)

SendBytesToHost(byt)

SetLineSize()

Case Else

byt(1) = TN_WONT

byt(2) = RcvBuf(i)

SendBytesToHost(byt)

End Select

Case TN_DONT 'Server asking you to NOT do something

'ToChatWindow(" TN_DONT" & Str(buffer(i + 1)) & vbCrLf)

byt(1) = TN_WONT

i += 1

byt(2) = RcvBuf(i)

SendBytesToHost(byt)

Case TN_WILL 'Server telling you it will do something

'ToChatWindow(" TN_WILL" & Str(buffer(i + 1)) & vbCrLf)

byt(1) = TN_DONT

i += 1

byt(2) = RcvBuf(i)

SendBytesToHost(byt)

Case TN_WONT 'Server telling you it won't do someting

'ToChatWindow(" TN_WONT" & Str(buffer(i + 1)) & vbCrLf)

byt(1) = TN_DONT

i += 1

byt(2) = RcvBuf(i)

SendBytesToHost(byt)

End Select

Case Else

Try

Threading.Thread.Sleep(Throttle)

'Debug.Write(ASCII.GetString(RcvBuf, i, 1))

Ser.Write(RcvBuf, i, 1)

Catch ex As Exception

WriteStatus("----------------------------")

WriteStatus("Routine: ReceiveCallBack")

WriteStatus("Exception: " & ex.Message)

WriteStatus("Chat Msg: " & Chr(RcvBuf(i)))

End Try

End Select

End Sub

Private Sub SetLineSize()

'The syntax for the subnegotiation is: IAC SB NAWS WIDTH[1] WIDTH[0] HEIGHT[1] HEIGHT[0] IAC SE

Dim byt() As Byte = {TN_IAC, TN_SB, TN_NAWS, LineSize \ 256, LineSize Mod 256, 0, 24, TN_IAC, TN_SE}

SendBytesToHost(byt)

End Sub

Private Sub SendBytesToHost(ByVal byt() As Byte)

TcpClt.Send(byt, byt.Length, SocketFlags.None)

End Sub

Private Sub HangUp(ByVal local As Boolean)

MdmErr = OK

If Not TcpClt Is Nothing Then

Try

TcpClt.Shutdown(SocketShutdown.Both)

TcpClt.Close()

TcpClt = Nothing

MdmErr = NO_CARRIER

If local = True Then

WriteStatus("Locally initiated disconnect")

Else

WriteStatus("Remote initiated disconnect")

End If

Catch ex As Exception

WriteStatus("Locally initiated disconnect, already offline")

End Try

Else

WriteStatus("Locally initiated disconnect, already offline")

End If

MdmCmdMode = True

Debug.WriteLine(MdmCmdMode.ToString)

End Sub

'Routine to write status to console window...

'and to log file if set.

Private Sub WriteStatus(ByVal msg As String)

Dim dt As String = Date.Now.ToShortDateString & " " & Date.Now.ToShortTimeString

msg = dt & " - " & msg

Console.WriteLine(msg)

Exit Sub

If keepLog = True Then

Dim sw As New StreamWriter(logFile, True)

'w = My.Computer.FileSystem.OpenTextFileWriter(logFile, True)

sw.WriteLine(msg)

sw.Close()

End If

End Sub

Private Sub SerRcvEvent(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs) Handles Ser.DataReceived

SerByt = Ser.BytesToRead

Ser.Read(XmtBuf, 0, SerByt)

Dim rcvString As String = ASCII.GetString(XmtBuf, 0, SerByt)

Debug.Write(rcvString)

' --Did we get a Modem Esc Command?

' If so, start the 1 second timer.

If InStr(rcvString, "+++") Then

swGuardTimer.Start()

End If

' --If we're in command mode, send characters received to be processed

If MdmCmdMode = True Then

ProcessMdmCmd(rcvString)

Exit Sub

End If

' --Otherwise, send it out to our connected user.

If TcpClt Is Nothing Then Exit Sub

Try

TcpClt.Send(XmtBuf, SerByt, SocketFlags.None)

Catch

End Try

End Sub

Private Sub ProcessMdmCmd(ByVal CmdStr As String)

MdmErr = OK

MdmCmdStr += UCase(CmdStr)

If MdmEcho = ModemEcho.EchoOn Then Ser.Write(CmdStr)

'--Command is still coming in if we haven't received the CR

If Right(MdmCmdStr, 1) <> Chr(13) Then Exit Sub

'--CR only does not a command make...

If MdmCmdStr.Equals(vbCr) Then

MdmCmdStr = ""

Exit Sub

End If

'--Get rid of the +'s from the ESC sequence, and trim off the CR

MdmCmdStr = MdmCmdStr.Replace("+", "").Trim(Chr(13))

Debug.WriteLine("MdmCmdStr: " & MdmCmdStr)

'--All good command strings begin with AT

If Left(MdmCmdStr, 2) <> "AT" Then

Debug.WriteLine("MdmCmdStr doesn't begin with AT")

MdmCmdStr = ""

ModemError(ERR)

Exit Sub

End If

'--Sometimes they just type AT to see if the modem is responding.

If MdmCmdStr = "AT" Then

MdmCmdStr = ""

ModemError(OK)

Exit Sub

End If

'--Now start dealing with the command strings...

Dim tmpCmd As String

If InStr(MdmCmdStr, "ATA") Then

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "ATD ") Or InStr(MdmCmdStr, "ATDT ") Then

GoDialOut(MdmCmdStr)

MdmCmdStr = ""

Exit Sub

End If

If InStr(MdmCmdStr, "ATI") Then

Ser.Write("Internet Modem Emulator v" & ver & " by Terry Olsen" & vbCr)

MdmErr = OK

MdmCmdStr = ""

'Exit Sub

End If

If InStr(MdmCmdStr, "AT&V") Then

Ser.Write("This will be our &V display page." & vbCr)

MdmErr = OK

MdmCmdStr = ""

'Exit Sub

End If

If InStr(MdmCmdStr, "ATZ") Then

HangUp(True)

MdmCmdMode = True

MdmHookState = ModemHookState.OnHook

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "E") Then

tmpCmd = Mid(MdmCmdStr, InStr(MdmCmdStr, "E") + 1, 1)

Debug.Write("E" & tmpCmd & ":")

If Val(tmpCmd) > 1 Then

MdmErr = ERR

Else

MdmEcho = Val(tmpCmd)

End If

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "H") Then

tmpCmd = Mid(MdmCmdStr, InStr(MdmCmdStr, "H") + 1, 1)

Debug.Write("H" & tmpCmd & ":")

If Val(tmpCmd) > 1 Then

MdmErr = ERR

Else

MdmHookState = Val(tmpCmd)

HangUp(True) 'True = Locally initiated disconnect

End If

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "Q") Then

tmpCmd = Mid(MdmCmdStr, InStr(MdmCmdStr, "Q") + 1, 1)

Debug.Write("Q" & tmpCmd & ":")

If Val(tmpCmd) > 1 Then

MdmErr = ERR

Else

MdmEcho = Val(tmpCmd)

End If

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "S0") Then

tmpCmd = Mid(MdmCmdStr, InStr(MdmCmdStr, "S0=") + 3, 1)

Debug.Write("S0=" & tmpCmd & ":")

If Val(tmpCmd) > 1 Then

MdmErr = ERR

Else

MdmRingMode = Val(tmpCmd)

End If

MdmCmdStr = ""

End If

If InStr(MdmCmdStr, "V") Then

tmpCmd = Mid(MdmCmdStr, InStr(MdmCmdStr, "V") + 1, 1)

Debug.Write("V" & tmpCmd & ":")

If Val(tmpCmd) > 1 Then

MdmErr = ERR

Else

MdmResultCodeFormat = Val(tmpCmd)

End If

MdmCmdStr = ""

End If

ModemError(MdmErr)

End Sub

Private Sub ModemError(ByVal code As Integer)

If MdmResultCodes = ModemResultCodes.Enabled Then

If MdmResultCodeFormat = ModemResultCodeFormat.Text Then

Debug.WriteLine("MdmErrCode: " & MdmErrorCode(code))

Ser.Write(vbCr & MdmErrorCode(code))

If code = 1 Then Ser.Write(" " & MdmBaud)

Ser.Write(vbCr)

Else

Ser.Write(vbCr & code & vbCr)

Debug.WriteLine("MdmErrCode: " & code)

End If

End Sub

Private Sub GoDialOut(ByVal cmd As String)

Dim port As Integer

Dim IP As IPAddress

Dim host As String

'--First, get rid of the AT command

cmd = cmd.Replace("ATDT ", "").Trim

cmd = cmd.Replace("ATD ", "").Trim

cmd = cmd.Trim(Chr(13))

'Debug.WriteLine("CMD=" & cmd)

'--Next, see if a port is specified

cmd = cmd.Replace(",", ":") 'Change comma separator to colon

cmd = cmd.Replace(" ", ":") 'change space separator to colon

'Debug.WriteLine("CMD=" & cmd)

'--Define the port we'll use to dial out

If cmd.Contains(":") Then

port = Val(Mid(cmd, InStr(cmd, ":") + 1))

cmd = cmd.Remove(cmd.IndexOf(":"))

Else

port = 23

End If

'Debug.WriteLine("CMD=" & cmd)

'Debug.WriteLine("PORT=" & port)

'Exit Sub

'--Now we check what kind of address we have. It could be:

' hostname.com, xx.xxx.xx.x, or WWWXXXYYYZZZ

Dim IpNoDots As Boolean = True

If Not cmd.Contains(".") Then

If cmd.Length = 12 Then

For i As Integer = 1 To 12

If Not (Mid(cmd, i, 1) >= "0" And Mid(cmd, i, 1) <= "9") Then

IpNoDots = False : Exit For

End If

If IpNoDots = True Then

cmd = cmd.Insert(9, ".")

cmd = cmd.Insert(6, ".")

cmd = cmd.Insert(3, ".")

End If

'Debug.WriteLine("CMD=" & cmd)

'Debug.WriteLine("PORT=" & port)

'Exit Sub

'--By the time we get here, we should have either a hostname or

' an IP address in the form of xxx.xx.xx.x

Try

IP = Dns.GetHostEntry(cmd).AddressList(0)

Try

host = Dns.GetHostEntry(IP).HostName

Catch

host = cmd

End Try

WriteStatus("Dialing: " & host & " (" & IP.ToString & ") on port " & port.ToString)

Catch ex As SocketException

WriteStatus("Error dialing " & cmd & ":" & port.ToString)

WriteStatus("Error message:" & ex.Message)

ModemError(NO_DIAL_TONE)

Exit Sub

End Try

MdmCmdMode = False

Dim IPE As New IPEndPoint(IP, port)

Try

TcpClt = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)

TcpClt.BeginConnect(IPE, AddressOf DialOutConnected, Nothing)

Catch ex As SocketException

ModemError(NO_DIAL_TONE)

WriteStatus(ex.Message)

End Try

End Sub

Private Sub DialOutConnected(ByVal ar As IAsyncResult)

Try

TcpClt.EndConnect(ar)

Catch ex As SocketException

WriteStatus(ex.Message)

MdmCmdMode = True

ModemError(NO_ANSWER)

Exit Sub

End Try

WriteStatus("Connection established.")

ModemError(CONNECT)

TcpClt.BeginReceive(RcvBuf, 0, RcvBuf.Length, SocketFlags.None, AddressOf ReceiveCallback, RcvBuf)

End Sub

Private Sub swGuardTimerFired(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs)

swGuardTimer.Stop()

If Ser.BytesToRead < 1 Then

MdmCmdMode = True

ModemError(OK)

Else

MdmCmdMode = False

If TcpClt Is Nothing Then Exit Sub

TcpClt.Send(XmtBuf, SerByt, SocketFlags.None)

End If

End Sub

End Module