[RESOLVED] Serial Port Read Index Out Of Range Exception

[pourkascheff]

Well, Hello. It's me again.
Consider a half-duplex modbus RTU serial communication between two devices which we want to only listen. A repeater.
Without any CRC/Checksum complexity, I stuck at the beginning. What is the best approach to do such thing?

Here's the code so far but making 2 bytes to an integer applies for first 8 bytes and then an exception will occur for line #30 which is comparing it is a HoldingRegister or not (Correct received package). I mean using Try/Catch will do the matter for first 8 bytes and continues the loop. I need the whole data. Any clues is precious. Thanks in advanced.

Public Class Form1
 
    Private Buffer As Byte()    'I'M NOT SURE IT IS THE BEST WAY TO DECLARE A BYTE ARRAY WITH UNKNOWN/CHANGABLE LENGTH OR NOT
    
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Control.CheckForIllegalCrossThreadCalls = False 'FOR ERRORS FROM NOWHERE(?)
        Try
            If SerialPort1.IsOpen = False Then
            SerialPort1.Open()
            End If
        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Critical)
            Application.Exit()
        End Try
    End Sub
 
    Private Sub SerialPort1_DataReceived(sender As Object, e As IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        If BackgroundWorker1.IsBusy = False Then
            BackgroundWorker1.RunWorkerAsync()  'IT'S GOING TO BE A VERY CROWDY CODE. LET THE BACKGROUNDWORKER DO THE LOOP THING FOR ME
        End If
    End Sub
    
    Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim byteCount = SerialPort1.BytesToRead 'GET INPUT BUFFER SIZE
        If SerialPort1.BytesToRead > 8 Then 'IGNORE BLANK AND NOT REQUEST COMMANDS (GET ONLY ANSWERS FROM SLAVES. REQUEST COMMANDS ARE 8 BYTES)
            buffer = New Byte(byteCount) {}     'EXTEND VARIABLE/ARRAY AS IT IS
            SerialPort1.Read(Buffer, 0, byteCount)  'READ SERIAL PORT FUNCTION
            Dim UserControl as UserControl() = {UserControl1, UserControl2, UserControl3, UserControl4, UserControl5, UserControl6, UserControl7, UserControl8, UserControl9, UserControl10, UserControl11, UserControl12, UserControl13, UserControl14}    'THERE ARE 14 USERCONTROLS WHICH SORTING VALUES IN THEM IS REQUIRED
            
            If Buffer(1) = 3 And Buffer(2) = 192 Then 'CORRECT PACKET(S) INCOMING
            
                If Buffer(0) = 2 Then   'FIRST PARAMETER               
                    For i = 0 To 29 Step 2  'ARRANGING/ASSIGNING VALUES IN THEIR PLACES FOR 14 USERCONTROLS
                    UserControl(i/2).TextBox1.Text = (Val(Buffer(i+3)*256) + Val(Buffer(i+4))   'COMBINE 2 BYTES => INTEGER
                    Next                
                End If
                
                'If Buffer(0) = 3 Then  'SECOND PARAMETR
                ''SAME AS ABOVE
                'End If
                '.
                '.
                '.
                'If Buffer(0) = n Then  'LAST PARAMETR
                ''SAME AS ABOVE
                'End If
            End If
    'POSSIBLE 'BUFFER' DISPOSE/CLEAR CODE GOES HERE WHICH I DON'T KNOW HOW TO DO IT
        End If
    End Sub 
End Class

Exception full message:
IndexOutOfRangeException was unhandled by user code: Index was outside the bounds of the array.

[Delaney]

check for the value of bytecount and SerialPort1.BytesToRead

by the way, you don't need bytecount, you can replace it everywhere by SerialPort1.BytesToRead,

check buffer after line 27, you may read nothing

[pourkascheff]

check for the value of bytecount and SerialPort1.BytesToRead

Hum, Is it possible that my stream broken or delayed a few milliseconds?

by the way, you don't need bytecount, you can replace it everywhere by SerialPort1.BytesToRead,

I remember I used all as SerialPort1.BytesToRead once and it didn't work. That's why, but when you say so, I will follow. I remember you sir from lots of SerialPort threads. Merci beaucoup

check buffer after line 27, you may read nothing

Is there any debugging tool included in Visual Studio? I believe I saw a list of parameters/variables below the screen. Buffer length was 2. Bingo, You might be exact on faultfinding. I'm going to check it.
You already read the whole code? Could it be something else?

I used SerialPort1_ReceivedData event. How can I switchover on something that waits to get like 300 bytes then take action? Legendary timers came to my head at the beginning why? because input buffer may be fully received and raw data ready to be processed. (Relax, my read data cycle is too slow)

Or how about increasing BytesToRead condition on equal and greater than an acceptable value like If SerialPort1.BytesToRead > 300 Then in line #23?

[dbasnett]

See this post and also the link contained in it.

https://www.vbforums.com/showthread....=1#post5569657

[Delaney]

Is there any debugging tool included in Visual Studio?

there are 3 ways:
1 - you include some messagebox with the variable to check it
2 - you click on the grey column on the left of the column with line number (must be a line with code), a red dot will appear and it will put a stop in you code when you run it and you will be able to check the values of the variable
3 - put the keyword "stop" in you code. it does the same than the red dot.

[pourkascheff]

See this post and also the link contained in it.

It is a bit complicated sir. But one of its advantages is "Dim readBuf(TheSP.BytesToRead - 1) As Byte".

Exception now occurs here:


I only acknowledged that my index=14 (in Buffer(index+4)) exceeds Buffer.Length=16 and causing error but not sure what to do.
What are my options?

[Delaney]

the picture is small, so we can barely see anything.

you need to think a little bit about what you do : why your index should go over the buffer length? I saw that you coded the upper limit of the index (20 or 29, i can't see well) where you should have a limit linked to the buffer length: for index =0 to buffer.length-4 step 3...

[pourkascheff]

Well, it turned out data stream was broken to pieces based on a port spy app monitored (still not sure why. Maybe timeout/nulldicard/Readbuffersize or other SerialPort control parameters) Mimicking a code in which be looking for an exact combination of bytes and extracting them from a random stream, Rectifies the matter.

Here the index in outer "for" called 'j' will be followed by another index which represents buffer subset current position:

'LOOP START
Dim UserControl as UserControl() = {UserControl1, UserControl2, UserControl3, UserControl4, UserControl5, UserControl6, UserControl7, UserControl8, UserControl9, UserControl10, UserControl11, UserControl12, UserControl13, UserControl14}
Dim Buffer(SerialPort1.BytesToRead -1) As Byte
SerialPort1.Read(Buffer, 0, Buffer.Length)
Try
    For j = 0 To Buffer.Length
        If Buffer(j) = 3 And Buffer(j + 1) = 192 Then
        TextBox1.Clear()
            If Buffer(j - 1) = 2 Then
            TextBox1.text = TextBox1.text & "PARAMETER="
                For i = j + 2 to 29 Step 2
                TextBox1.text = TextBox1.text & (Buffer(i)*256) + Buffer(i + 1) & ", "
                UserControl((i - 3)/2).Label1.Text = (Buffer(i)*256) + Buffer(i + 1)
                Next
            End If
        End If
    Next
Catch ex As Exception
End Try
'LOOP END