[RESOLVED] Can I send data via com ports?

[Doogle]

Ok the cable sounds good.
Here's some code, obviously not tested but compiles clean. There are 2 Forms:

frmReceiver with a CommandButton named cmdStart and an MSComm control, named MSComm1 it uses CommPort 2. This form should be the start-up form for the project.

'
' Simple Text File Transfer using Serial Port
' Receiver Code
'
Option Explicit
Private boTransfer As Boolean
Private intFile As Integer

Private Sub cmdStart_Click()
'
' Load and position the Sender form
'
Load frmSender
frmSender.Visible = True
frmSender.Caption = "Sender"
frmSender.Left = Me.Left + Me.Width
frmSender.Top = Me.Top
End Sub

Private Sub Form_Load()
MSComm1.CommPort = 2
MSComm1.Settings = "9600,N,8,1"
MSComm1.RThreshold = 1
MSComm1.PortOpen = True
Me.Caption = "Receiver"
End Sub

Private Sub MSComm1_OnComm()
Static strBuffer As String
Static intLen As Integer
Static intCount As Integer
Dim strData As String
Dim strRecord As String
Dim strChar As String
Dim lngPos As Long
Dim intChar As Integer
Dim boFinished As Boolean
Dim strUnblock() As String
Select Case MSComm1.CommEvent
    Case comEvReceive
        '
        ' At least RThreshold bytes are available to be read
        ' Read and append them to the buffer
        '
        strData = MSComm1.Input
        strBuffer = strBuffer & strData
        Select Case boTransfer
            Case False
                '
                ' We're in Command Mode
                '
                Do
                    lngPos = InStr(strBuffer, Chr(4))
                    '
                    ' There's at least 1 complete record
                    ' Unblock it
                    '
                    If lngPos > 0 Then
                        strRecord = Mid$(strBuffer, 1, lngPos - 1)
                        strUnblock = Split(strRecord, Chr(2))
                        Select Case strUnblock(0)
                            Case "FT"
                                '
                                ' File Transfer Command
                                ' Save the file size and open a file to receive
                                ' Switch the transfer flag on
                                '
                                intLen = CLng(strUnblock(1))
                                Open "C:\MyTextRX.txt" For Output As intFile
                                boTransfer = True
                                '
                                ' We can add other commands here
                                '
                        End Select
                        '
                        ' Check if there's anything else in the buffer
                        ' if there is then move it to the front and
                        ' go round the loop.
                        ' Otherwise flush the buffer and exit
                        '
                        If lngPos < Len(strBuffer) Then
                            strBuffer = Mid$(strBuffer, lngPos + 1)
                        Else
                            strBuffer = ""
                            boFinished = True
                        End If
                    Else
                        '
                        ' Didn't find a complete record
                        ' exit and wait for the next comEvReceive event
                        '
                        boFinished = True
                    End If
                Loop Until boFinished = True
            Case True
                    '
                    ' We're in Transfer mode
                    ' The data is being blocked by the sender (a line at a time)
                    ' Each block is terminated by a Chr(4)
                    ' so we accumulate the data until Chr(4) is received
                    ' and then write the complete record to the file,
                    ' flush the buffer, and ask the sender for the next block
                    '
                    Do
                        lngPos = InStr(strBuffer, Chr(4))
                        If lngPos > 0 Then
                            strRecord = Mid$(strBuffer, 1, lngPos - 1)
                            Put #intFile, , strRecord
                            intCount = intCount + Len(strRecord)
                            labProgress.Caption = CStr(intCount) & " Bytes Received"
                            DoEvents
                            If intCount >= intLen Then
                                Close intFile
                                boTransfer = False
                                intLen = 0
                                intCount = 0
                                boFinished = True
                            End If
                            If lngPos < Len(strBuffer) Then
                                strBuffer = Mid$(strBuffer, 1, lngPos + 1)
                            Else
                                strBuffer = ""
                                boFinished = True
                            End If
                        Else
                            boFinished = True
                        End If
                        
                    Loop Until boFinished = True
                    '
                    ' Processed this buffer so tell the sender
                    ' we're ready for the next one
                    '
                    MSComm1.Output = "OK" & Chr(4)
                    
                        
        End Select
End Select
End Sub

frmSender with a CommandButton named cmdSend and an MSComm Control named MSComm1 and uses CommPort 1

'
' Simple Text File transfer using Serial Port
' Sender Code
'
Option Explicit
Private boTransfer As Boolean
Private intFile As Integer

Private Sub cmdSend_Click()
Dim intLen As Integer
intFile = FreeFile
Open "C:\MyText.txt" For Input As intFile
intLen = LOF(intFile)
MSComm1.Output = "FT" & Chr(2) & CStr(intLen) & Chr(4)
End Sub

Private Sub Form_Load()
MSComm1.CommPort = 1
MSComm1.Settings = "9600,N,8,1"
MSComm1.RThreshold = 1
MSComm1.PortOpen = True
End Sub

Private Sub MSComm1_OnComm()
Dim strFileData As String
Dim strData As String
Dim strRecord As String
Static strBuffer As String
Dim lngPos As Long
Dim boFinished As Boolean
Select Case MSComm1.CommEvent
    Case comEvReceive
        strData = MSComm1.Input
        strBuffer = strBuffer & strData
        Do
            lngPos = InStr(strBuffer, Chr(4))
            If lngPos > 0 Then
                strRecord = Mid$(strBuffer, 1, lngPos - 1)
                Select Case strRecord
                    Case "OK"
                        '
                        ' Every time we get an "OK" from the receiver
                        ' send the next line of the file
                        '
                        If Not EOF(intFile) Then
                            Line Input #intFile, strFileData
                            '
                            ' Since we're only ever sending text files
                            ' we need to add the vbCrLf
                            ' since Line Input will have stripped them off
                            '
                            MSComm1.Output = strFileData & vbCrLf & Chr(4)
                            labProgress.Caption = CStr(Len(strFileData) + 2) & " Bytes Sent"
                            DoEvents
                        Else
                            Close intFile
                        End If
                End Select
                If lngPos < Len(strBuffer) Then
                    strBuffer = Mid$(strBuffer, 1, lngPos + 1)
                Else
                    strBuffer = ""
                    boFinished = True
                End If
            Else
                boFinished = True
            End If
        Loop Until boFinished = True
End Select
End Sub

Run the Project and click the Start Button on the Receiver, the Sender form should appear next to it. Click on the Send button on the Sender and the transfer should take place. It sends C:\MyText.txt to C:\MyTextRX.txt but obviously you can change the names etc.

I suspect (know) there'll be a few problems (I've never got anything to work first time as far as I can remember) so let me kow what problems you encounter

Disclaimer: This implementation is *very* inefficient, since it is sending a byte at a time and the Receiver sends more data than the Sender, and shouldn't be used 'in anger'. It is meant purely as an example of the logic involved. A 'proper implementation' would use Byte Arrays and buffering of data. Perhaps I'll tidy it up a bit.