How to solve System.Timeout.Exception on a PBX SMDR Capture app?

The port connection is successful but when it gets to receive data I get this timeout exception. Got no idea what to do...what to fix. Need help.

System.TimeoutException: The operation has timed out.
at System.IO.Ports.SerialStream.Read(Byte[] array, Int32 offset, Int32 count, Int32 timeout)
at System.IO.Ports.SerialStream.Read(Byte[] array, Int32 offset, Int32 count)
at System.IO.Ports.SerialPort.InternalRead(Char[] buffer, Int32 offset, Int32 count, Int32 timeout, Boolean countMultiByteCharsAsOne)
at System.IO.Ports.SerialPort.ReadTo(String value)
at System.IO.Ports.SerialPort.ReadLine()
at SMDR_Capture.SerialPortDataReceive.ReadFromCom() in e:\punn\my documents\visual studio 2010\Projects\SMDR Capture\SMDR Capture\SMDR Capture.vb:line 165

Below you have the Visual Basic.NET 2010 project solution in .doc (word 2003) file.
Don't know how to put code here in tags thus I had to manage with an attachment if you happen not see any attachment I'll manage another way of uploading a link and post in comment.

To put code in code tags you either use the # icon on the advanced editor or you simply type them in around your code like it shows in my signature.

Without having sow the code I would say that the most likely issue is that you are telling it to read from the port without first checking to see if there is anything there to read.

You also may want to look at your readtimeout setting on the serialport object in your code.

The code is already uploaded in an attachment...and for my account I don't see any advanced editor so I can put #before code so that it can generate a code view...I previously had review of people who commented in my post regarding not proper code post so I chose to upload it in attachment and beside the code is a bit long. Its virus/trojan/malware free doc, word file I guarentee 100%. Yeah I did the .ReadTimeout = 11000 more than the BaudRate (9600) but still I was getting that error...as for the other opinion i really havent got an idea how to...

All you have to do is type in the code tags

[code]Some code here[/code]

gives you

Code:

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Some code here

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I do not like to download files, especially ones that can have embedded scripts. No need for it.

Is your read code in the data received event or somewhere else?

As to your issue, I notice in the error message you are using readline() this may result in an error if the newline character is not received within the timeout period even if there was data there to read as it will try to read up to a newline character which is by default a line feed character CHR(10)

Ok here we go.

Code:

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Imports System
Imports System.IO.Ports
Imports System.Threading
Imports System.Threading.Thread
Imports System.Runtime.InteropServices
Imports System.ComponentModel

Public Class SerialPortDataReceive

#Region "SerialPort"
    Dim RS232 As New SerialPort
    Dim readThread As Thread = New Thread(AddressOf ReadFromCom)
    Dim abortThread As Boolean
   
    Private Sub ProgramClosing(ByVal sender As Object, ByVal e As ComponentModel.CancelEventArgs) Handles MyBase.Closing
        If MessageBox.Show("Do you really want to close the window?", "SMDR Capture", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.No Then
            e.Cancel = True
        Else
            ' Close COM port on a new thread when the form is terminated with [X]
            Dim t As New Thread(AddressOf ClosePort)
            t.Start()
        End If
    End Sub
    Private Sub ClosePort()
        If RS232.IsOpen = True Then RS232.Close()
    End Sub

    'Private Sub SerialPortDataReceive_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
    '    If MessageBox.Show("Do you really want to close the window", "SMDR Capture", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.No Then
    '        e.Cancel = True
    '    Else
    '        ' Close COM port on a new thread when the form is terminated with [X]
    '        If RS232.IsOpen = True Then
    '            RS232.Close()
    '        End If
    '    End If
    'End Sub

    Private Sub SerialPortDataReceive_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        For Each COMPort As String In My.Computer.Ports.SerialPortNames
            cmbPort.Items.Add(COMPort)

        Next

        'Filling combo box Baud Rate with exact numbers predefined earlier. (Mbush combo box-in e Baud Rate me numra ekzakte te paradefinuara.)

        cmbBaud.Items.Add("2400")
        cmbBaud.Items.Add("4800")
        cmbBaud.Items.Add("7200")
        cmbBaud.Items.Add("9600")
        cmbBaud.Items.Add("19200")
        cmbBaud.Items.Add("38400")
        cmbBaud.Items.Add("57600")


        'Filling combo box Parity with exact values predefined earlier. (Mbush combo box-in e Parity me vlera ekzakte te paradefinuara.)
        cmbParity.Sorted = True

        cmbParity.Items.Add("None")
        cmbParity.Items.Add("Odd")
        cmbParity.Items.Add("Even")
        cmbParity.Items.Add("Mark")
        cmbParity.Items.Add("Space")

        'Filling combo box Data Bits with exact values predefined earlier. (Mbush combo box-in e Data Bits me vlera ekzakte te paradefinuara.)
        cmbData.Sorted = True

        cmbData.Items.Add("8")
        cmbData.Items.Add("7")
        cmbData.Items.Add("6")
        cmbData.Items.Add("5")
        cmbData.Items.Add("4")

        'Filling combo box Stop Bits with exact values predefined earlier. (Mbush combo box-in e Stop Bits me vlera ekzakte te paradefinuara.)
        cmbStop.Sorted = True

        cmbStop.Items.Add("None")
        cmbStop.Items.Add("1")
        cmbStop.Items.Add("1.5")
        cmbStop.Items.Add("2")

        cmbPort.SelectedIndex = 0
        cmbBaud.SelectedIndex = 3
        cmbParity.SelectedIndex = 2
        cmbData.SelectedIndex = 4
        cmbStop.SelectedIndex = 0


        'RS232 = srpPBX
        'With RS232
        '    .PortName = "COM16"
        '    .BaudRate = 9600
        '    .Parity = Parity.None
        '    .DataBits = 8
        '    .StopBits = 1
        '    .ReadTimeout = 500
        '    .DtrEnable = True
        'End With
    End Sub

    Private Sub btnOpenClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOpenClose.Click
        If cmbPort.SelectedItem = True Then
            Try
                If btnOpenClose.Text Is "Open" Then
                    If chkbDTR.Checked = True AndAlso chkbRTS.Checked = True Then

                        RS232 = srpPBX
                        RS232.PortName = cmbPort.Text()
                        RS232.BaudRate = CInt(cmbBaud.Text)
                        RS232.Parity = CType([Enum].Parse(GetType(Parity), cmbParity.Text), Parity)
                        RS232.DataBits = CInt(cmbData.Text)
                        RS232.StopBits = CInt(cmbStop.Text)
                        RS232.ReadTimeout = 11000
                        RS232.DtrEnable = True
                        RS232.RtsEnable = True

                        RS232.Open()

                        abortThread = False
                        readThread.Start()

                        btnOpenClose.Text = "Close"
                        tltPBX.SetToolTip(btnOpenClose, "Close communication")
                        txtReceive.ReadOnly = True
                        lblStatus.Text = "Connection succesfully opened on " & RS232.PortName & "."
                        cmbPort.Enabled = False
                        cmbBaud.Enabled = False
                        cmbParity.Enabled = False
                        cmbData.Enabled = False
                        cmbStop.Enabled = False


                    ElseIf MessageBox.Show("You haven't checked DTR and RTS which results no received data!", "SMDR Capture", MessageBoxButtons.RetryCancel, MessageBoxIcon.Warning) = Windows.Forms.DialogResult.Retry Then
                        chkbDTR.Checked = True
                        chkbRTS.Checked = True
                    End If

                ElseIf btnOpenClose.Text = "Close" Then
                    Try
                        RS232.Close()

                        abortThread = True

                        btnOpenClose.Text = "Open"
                        tltPBX.SetToolTip(btnOpenClose, "Open communication")
                        txtReceive.ReadOnly = False
                        lblStatus.Text = "Connection succesfully closed on " & RS232.PortName & "."
                        cmbPort.Enabled = True
                        cmbBaud.Enabled = True
                        cmbParity.Enabled = True
                        cmbData.Enabled = True
                        cmbStop.Enabled = True
                    Catch ex As Exception
                        MsgBox(ex.Message & vbCritical)
                    End Try
                End If
            Catch ex As Exception
                MsgBox("Another program is already using " & cmbPort.Text() & vbCrLf & vbCrLf & _
                      "Please try again later", MsgBoxStyle.OkOnly + MsgBoxStyle.Information, cmbPort.Text() & " is not available")


            End Try
        Else
            MessageBox.Show("You haven't selected any of the available ports or process terminated since there is no available port!", "Parameter Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        End If
       
    End Sub

    Public Sub ReadFromCom()
        While abortThread = False
            Try
                Dim message As String = RS232.ReadLine
                updateStatus("Received: " & message)
            Catch ex As TimeoutException
                updateStatus(ex.ToString)
            End Try
        End While
    End Sub

    Public Delegate Sub updateStatusDelegate(ByVal newStatus As String)
    Public Sub updateStatus(ByVal newStatus As String)
        If Me.InvokeRequired Then
            Dim upbd As New updateStatusDelegate(AddressOf updateStatus)
            Me.BeginInvoke(upbd, New Object() {newStatus})
        Else
            Try
                txtReceive.Text = newStatus & vbCrLf & vbCrLf & txtReceive.Text
                My.Computer.FileSystem.WriteAllText("C:\Users\Punn\Desktop\SMDR_Error_Log.txt", txtReceive.Text, True)
            Catch ex As Exception
                MsgBox(ex.Message & vbCritical)
            End Try
           
        End If
    End Sub

#End Region
#Region "Initializations"
    Private Sub txtReceive_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtReceive.TextChanged

    End Sub

    Private Sub lblPort_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblPort.Click

    End Sub

    Private Sub lblBaud_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblBaud.Click

    End Sub

    Private Sub lblParity_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblParity.Click

    End Sub

    Private Sub lblData_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblData.Click

    End Sub

    Private Sub lblStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblStop.Click

    End Sub

    Private Sub cmbPort_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbPort.SelectedIndexChanged

    End Sub

    Private Sub cmbBaud_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbBaud.SelectedIndexChanged

    End Sub

    Private Sub cmbParity_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbParity.SelectedIndexChanged

    End Sub

    Private Sub cmbData_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbData.SelectedIndexChanged

    End Sub

    Private Sub cmbStop_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbStop.SelectedIndexChanged

    End Sub

    Private Sub chkbDTR_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkbDTR.CheckedChanged

    End Sub

    Private Sub chkbRTS_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkbRTS.CheckedChanged

    End Sub

    Private Sub lblEvents_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblEvents.Click

    End Sub

    Private Sub grbConn_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles grbConn.Enter

    End Sub

    Private Sub grbReceived_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles grbReceived.Enter

    End Sub

    Private Sub msSerialPortDataReceive_ItemClicked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ToolStripItemClickedEventArgs) Handles msSerialPortDataReceive.ItemClicked

    End Sub

    Private Sub OpenToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OpenToolStripMenuItem.Click

    End Sub

    Private Sub SaveToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SaveToolStripMenuItem.Click

    End Sub

    Private Sub ExitToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitToolStripMenuItem.Click
        If MessageBox.Show("Do you really want to close the window", "SMDR Capture", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
            Dim t As New Thread(AddressOf ClosePort)
            t.Start()
            Application.Exit()
            'Else
            '    Dim e1 As ComponentModel.CancelEventArgs
            '    e1.Cancel = True
            ' Close COM port on a new thread when the form is terminated with [X]

        End If
    End Sub

    Private Sub AboutToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AboutToolStripMenuItem.Click
        Dim F As New frmAbout
        F.Show()
    End Sub

    Private Sub lblStatus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblStatus.Click

    End Sub


    Private Sub timerStatus_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles timerStatus.Tick
        Try
            If RS232.IsOpen Then
                lblStatus.Text = ""
            Else
                lblStatus.Text = ""
            End If
        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, Me.Text)
        End Try
    End Sub
#End Region

End Class

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Yeah I used readline() to read from serialport and no the data receive is not in the DataReceived Event of the SerialPort. Try a new project with this code and tell me how can you fix the error please. I'd be thankful to your kindness. =)

2 Things,

1: does the data being sent have line feeds?
2: You should be using the datareceived event of the serialport class and reading your data there.

Really I see no need for a second thread. I have did tons of serial based apps and never had an issue that would require a second thread.

Basically either use the data received event which will cause your program to only try to read data when data is there to read or optionally you could use a timer and poll the port using the btyestoreceive property to see if anything is waiting to be read and execute a read when this value >0

As is if you open the port you try to read never checking to see if anything is there or even if there is anything actually connected to the port, Your code will then try to read until it is closed by the user or gives up and throws an error.

The data sent doesn't have either LF or CR+LF...as for DataReceived Event should I write the readline code with the thread inside of it or should I completely drop that code down and write something else in DataReceived Event...I'm very new to this field of telephone/PBX/serialport programming thus it's hard to understand what I am supposed to do next. I'd be thankful if you can show me in code example of how you would write or manage to check if there's something to read in the port.

I did run my application today worked fine in the very first seconds of communication and it showed me this result : Received: 2/ 8/12 6:52PM 102 01 00491623746564 00:00'29" ....
but after that the same System.TimeoutException...

For starters I would comment out this line

Code:

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readThread.Start()

---

I would then add in the datareceived event of the serial port

Code:

---

Dim strMessage As String = RS232.ReadLine

txtReceive.Text = strMessage & vbCrLf & vbCrLf & txtReceive.Text

---

This may be fine but since there is no LF characters in your transmission it may not.

The other option is to use Read() instead of readline()
Read will require a bit more code since it returns a byte array rather than a string and will need to be converted before it is displayed.

I've made a research over the internet about Port.Read() method and made conversation to UTF-8(65001) and made few breakpoints where I thought I must and Debugged(F5) or Step Over(F10) and I saw there were 0 bytes in the buffer to read but I'm sure there are bytes to read since with Terminal or other application that I'm testing it shows me the log, caller id and etc etc stuff like that.

And here is my code to the DataReceived event of my serial port but there is a problem I don't know what to do, how to fire that event. I have a button designated to open the communication which after it opens sets the boolean value of SndRcv = True whereas in DataReceived event I made a While loop about that true/false statement of that bool obj.

I've completely removed the lines with .ReadLine and remove unnecessary threads.

Code below:

Code:

---

Private Sub srpPBX_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles srpPBX.DataReceived
        'This event will Receive the data from the selected COM port..
        Dim bRead, nRead As Integer ' Dim returnStr As String = ""
        Dim ascStr As String = ""
        Dim cData(bRead - 1) As Byte

        While SndRcv = True
            If e.EventType = System.IO.Ports.SerialData.Chars Then
                RS232.Encoding = System.Text.Encoding.GetEncoding(65001)
                bRead = RS232.BytesToRead 'Number of Bytes to read
                nRead = RS232.Read(cData, 0, bRead)  'Reading the Data

                For Each b As Byte In cData
                    ascStr += Chr(b)        'Ascii String
                Next
                txtReceive.Text = ascStr & vbCrLf & vbCrLf & txtReceive.Text
                My.Computer.FileSystem.WriteAllText("C:\Users\Punn\Desktop\SMDR_New_Log.txt", txtReceive.Text, True)
                RaiseEvent DataRecieved(ascStr)
            End If
        End While
    End Sub

---

So what's left is how to fire this event after the connection is successful?

There is nothing you need to do to fire the event. This event is controled by the property ReceivedBytesThreshold by default this is set to 1. The event will fire when at leaset this many bytes have been receive through the open port and only when this happens.

As for your new code there should not be a loop there. The event will fire when data is received. Your loop will just be a problem.

There is a single method to convert a byte array to a string so no need for that other loop that sets the characters either.

See Encoding.GetString()


The raiseevent statement should not be there either

It is really very simple. In your data received event you should have code to
Read the data that has just been received
If reading into a byte array then use the encoding class to convert that array to a string.
Do something with that string

This will happen each time data is received. No need to loop or call the event it will know when it is time.

When you want to stop receiving data you close the port.

Ok I think this is end I can get so far...but I don't get any result in my textbox...I removed the unnecessary loops and every other triggering just made the read data code into DataReceived.
Can you help me a little bit more...
Previous properties are : ReceivedDataThreshold = 1, DTR and RTS enabled and ReadTimeout = 500 (ms). When I run the other applications they show me data in the txtbox...but with the code I have no error but no result aswell...

Code:

---

Private Sub srpPBX_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles srpPBX.DataReceived
        'This event will Receive the data from the selected COM port..
        Dim n As Integer = RS232.BytesToRead()
        Dim comBuffer As Byte() = New Byte(n - 1) {}
        Dim BytesReceived As Integer   
        Try
            BytesReceived = RS232.Read(comBuffer, 0, n)

            If BytesReceived > 0 Then
                txtReceive.Text = txtReceive.Text + System.Text.Encoding.ASCII.GetString(comBuffer)
                'My.Computer.FileSystem.WriteAllText("C:\Users\albann\Desktop\SMDR_New_Log.txt", txtReceive.Text, True) output to a txt file for later use.
            End If
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message, ex.Source, MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

---

Looks much better but I am a bit confused by your naming in the code.

Code:

---

Private Sub srpPBX_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles srpPBX.DataReceived
        'This event will Receive the data from the selected COM port..
        Dim n As Integer = RS232.BytesToRead()
        Dim comBuffer As Byte() = New Byte(n - 1) {}
        Dim BytesReceived As Integer   
        Try
            BytesReceived = RS232.Read(comBuffer, 0, n)

            If BytesReceived > 0 Then
                txtReceive.Text = txtReceive.Text + System.Text.Encoding.ASCII.GetString(comBuffer)
                'My.Computer.FileSystem.WriteAllText("C:\Users\albann\Desktop\SMDR_New_Log.txt", txtReceive.Text, True) output to a txt file for later use.
            End If
        Catch ex As Exception
            MessageBox.Show("Error: " & ex.Message, ex.Source, MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

---

If your SerialPort is named srpPBX then this is what you need to read from.
If your serial port is named RS232 then this is what you need to handle the datareceived event for.

As is you are trying to read from a port named RS232 when data is received on a port named srpPBX. Clearly the result will not be what you are looking for.


Also I am a little confused by this line

Code:

---

Dim comBuffer As Byte() = New Byte(n - 1) {}

---

You do not need to specify the size and I have no idea why the {} is there.

I thought that too but wanted a confirmation from your reading of code...but I have an initialization up in my button click event where RS232 = srpPBX...and what do you suggest about byte I have to just simply Dim comBuffer as Byte and nothing else?

Code:

---

Dim ComBuffer() As Byte

---

Why are you setting RS232=srpBPX?

I see code that defines RS232 as a New SerialPort which is fine.
then you have code that sets RS232=srpPBX ??

srpPBX is not defined in the code that I can see. What is it?

All you have to do is
1: drag the serialport from the toolbox to the form
2: Give it a name if you like
3: Add some code for the settings if you like
4: Add some code somewhere to open and close the port
5: Select the serial port you added from the drop down on the left in the code editor
6: Choose datareceived from the drop down on the right
7: Add the code to receive the data.

btw if you are going to create the port through code rather than dropping the object from the toolbox then you need to define it with events to get the events to work.

Code:

---

Dim WithEvents MyPort As New System.IO.Ports.SerialPort

---

In this case all code references would use MyPort
If you drag the one from the toolbox and do not change its name then all code references would be to SerialPort1

In no case should you do both and then add code MyPort=SerialPort1

Ok I get things settle down but still no result in the txtbox. I've made a breakpoint on DataReceived event to see if it enters. YES, it does but when I press F11 and search line by line results it shows me in the brackets correct ones but passes to the exception by telling me that Cross-Thread Exception on the txtReceived. Now am I supposed to use Delegate Subs and Threadings with InvokeRequired methods?

DataMiser I'm so grateful and thankful to your help regarding Serial Port in specific PBX connections. I now came to the conclusion my code works way better no exceptions. All I needed was another Invoke method in DataReceived event since the txtReceive textbox control was being created and handled in another thread. One last question is there any option to setup in the PBX to record and not to discard previous information, like lets stay to send me the last month call log? I have installed the Maintenance Console of the PBX machine in my workplace but hard to understand find if there is an option like that.

I thought you were working with a single threaded app now? Cross threading exceptions only occur in multi thread apps.

I have no idea about PBX, don't even know what it is. I have did a lot of serial port programming for other things though.

Hello back again. Thanks again for the help on how to. Now I'm having a result interface problem on textbox control. The message that is carried on the txtbox from the PBX (through RS232 port) somehow gets twisted instead of the regular one line format and it's like this "2/20/12 11:00AM 101 02 < DISA incoming >

00:00'31" .... 0". (with one enter, 3 spaces and an another enter addition than normal one line format). Is there something that I can fix this on the bytes received or the machine interprets it like that randomly?

This is the line code where it converts bytes and adds them as a string to text box:

Code:

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txtReceive.Text = txtReceive.Text + x + vbNewLine

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You are adding a newline after every read. Is there anythign in your incoming data that would indicate when one line is done and the next one begins? If so you can check for this and add the newline in the correct place. As is in any given read you could get part of a line and a newline character would be added to it via your code breaking the line apart. I do not know enough about your incoming data stream to tell you how would be best to handle it.

This is where I convert bytes to ASCII string

Code:

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x = System.Text.Encoding.ASCII.GetString(comBuffer)

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and this is in the DataReceived event where it joins that string to the existing textbox text

Code:

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txtReceive.Text = txtReceive.Text + x + vbNewLine

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In txtReceive_TextChanged event there is this code aswell which I think it might interrupt the format of text :

Code:

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Private Sub txtReceive_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtReceive.TextChanged
        If Not txtReceive.Focused Then
            txtReceive.SelectionStart = txtReceive.Text.Length
            txtReceive.ScrollToCaret()
        End If
    End Sub

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The thing is that your code will add a line feed after every read from the port. It is always possible that a read will be a portion of what is coming more likely with longer strings and slower baud rates. Increasing the baud rate on both sides may help if that is possible but ideally you need to know where one line ends and the next begins and insert your lnewline there rather than blindly appending it to everything that comes in.

I've written an application to log phone calls for a NEC NEAX 2000 PBX phone system. I believe your phone system works very similar to the NEAX 2000 (the format of smdr data might be different though). Basically, the phone systems continuously sends data down its RS232 port whenever a call is completed. And thus, in the application, you just need to set your serial port's data receive threshold to the number of bytes as your smdr record length, then handle the serial port data received event. In that event handler, you just read n bytes (where n is the smdr record length) from the port and then parse it into meaningful data.
The serial port data received event is raised on a separate thread, and thus if you want to display the data on your UI you need to code it as such (that is, you can't access controls on the UI thread directly from another thread as you're doing now in the current code)

Yeah Stanav, indeed. But here's the question where do I know how much should I set the datareceived threshold number to, by default it's -1...i mean that the length of the bytes received varies , it's dynamic every time a call is recorded in the PBX (panosonic). But skip this what I encounter as a logical problem is that the call duration of outgoing calls (the ones that you dial to make calls) is very unpredictable. E.g. if I start a call to 044111111 (not a valid number) and the beep tone rings for like 4-5 sec and then the person picks up the phone hangs the call and makes the conversation for an interval of let's say 20 sec. In the call duration it will show me total of 25 sec where as 4-5 first seconds where the beep tone ones. That's a very big problem if e.g. there is an international outgoing call e.g. from my country to Germany one and it rings for 1 min and makes a conversation for 2 min, total of 3 min call duration , it will charge the call for 3 min which is not an accurate result. Have any similar problems encountered or solutions for this one? I'd be grateful to hear anything from you.

One would think that there is a byte or signal that signals the end of a stream you may want to save the data driectly to a file then look at it with a hex editor.

You mean not to convert the bytes array into ASCII but normally insert them as they are and save into text file and search with hex editor?

Yes just as a test so you can view the output in the hex editor and see exactly what you are getting. It is possible that you are getting something in the stream that you do not see in your textbox and can be used to determine where to add a newline.

Gotta test on monday since now i'm set home and away from the PBX machine in my workplace. Ill inform you by the results. Stay tuned. I hope I'm not annoying with this topic. =)