B4J Question Facing Problem with Jserial...Receiving Data is not in proper format

embedded said:

sometime only part of data is received remaining part is received in next event fired.

Click to expand...

emexes said:

Rather than relying on the network chunking aligning with your packets, instead just treat it as a stream of bytes.

Usually you'd do this by, for each incoming VB data_received event:
- append the received data to a string buffer
- while the string buffer contains an end-of-packet marker
- cut the (potential) packet from the front of the string buffer into maybe_packet
- if maybe_packet contains a start-of-packet marker then
- cut off any guff from the front of maybe_packet up to the start-of-packet marker
- handle maybe_packet

Click to expand...

emexes said:

might be a useful starting point for others, so:

If you use this packet parsing routine:

B4X:

Sub HandleIncomingData(Chunk As String)
    LogColor("In = " & Chunk.Replace(CRLF, "CRLF"), 0xFFc0c0c0)
    PacketBuffer = PacketBuffer & Chunk

Click to expand...

emexes said:

if I can find a readable MODBUS format specification

Click to expand...

Sub Process_Globals
    Dim StartOfPacket As String = ":"    'MODBUS ASCII packets start with colon
    Dim EndOfPacket As String = Chr(13) & Chr(10)    'MODBUS ASCII packets end with CR LF
    Dim PacketBuffer As String = ""
End Sub

Sub AStream_NewData (Buffer() As Byte)
    dim bc as ByteConverter
    PacketBuffer = PacketBuffer & bc.StringFromBytes(Buffer, "ISO-8859-1")    '1:1 byte:char conversion (UTF-8 also works for ASCII)

    Do While True
        Dim P As Int = PacketBuffer.IndexOf(EndOfPacket)    'check for packet in PacketBuffer
        If P < 0 Then Exit    'exit if not
   
        P = P + EndOfPacket.Length    'point to end of packet, not start of EndOfPacket marker
        Dim Packet As String = PacketBuffer.SubString2(0, P)    'copy packet from front of buffer
        PacketBuffer = PacketBuffer.SubString(P)    'remove packet from buffer
   
        P = Packet.LastIndexOf(StartOfPacket)
        If P > -1 Then    'if packet present
            If P <> 0 Then    'if guff before StartOfPacket
                Packet = Packet.SubString(P)    'then chop it off
            End If
            HandlePacket(Packet)
        End If
    Loop
End Sub

Sub HandlePacket(Packet As String)
    Dim Temp As String = Packet.Replace(Chr(13), "<CR>"),Replace(Chr(10), "<LF>")
    Log(DateTime.Now & Tab & Packet.Length & Tab & Temp)
ENd Sub

emexes said:

Assuming that your MODBUS is ASCII, this might both fix up your split packets, and parse out the packets for you:

B4X:

Sub Process_Globals
    Dim StartOfPacket As String = ":"
    Dim EndOfPacket As String = Chr(13) & Chr(10)
    Dim PacketBuffer As String
End Sub

Sub AStream_NewData (Buffer() As Byte)
    dim bc as ByteConverter
    PacketBuffer = PacketBuffer & bc.StringFromBytes(Buffer, "UTF8")

    Do While True
        Dim P As Int = PacketBuffer.IndexOf(EndOfPacket)    'check for packet in PacketBuffer
        If P < 0 Then Exit    'exit if not
     
        P = P + EndOfPacket.Length    'point to end of packet, not start of EndOfPacket marker
        Dim Packet As String = PacketBuffer.SubString2(0, P)    'cut off front bit
        PacketBuffer = PacketBuffer.SubString(P)    'keep the rest
     
        P = Packet.LastIndexOf(StartOfPacket)
        If P > -1 Then    'if packet present
            If P <> 0 Then    'if guff before StartOfPacket
                Packet = Packet.SubString(P)    'then chop it off
            End If
            Log(DateTime.Now & Tab & Packet.Length & Tab & Packet.Replace(Chr(13), "<CR>"),Replace(Chr(10), "<LF>")
        End If
    Loop
End Sub

We're not quite at the finish line, but we're coming 'round the home turn. ?

Click to expand...

embedded said:

Please give me any solution for that.

Click to expand...

- In other cases you should use AsyncStreams in regular mode. This means that there is no guarantee that each sent message will be received as a single message. In fact it is more or less guaranteed not to happen. So your code is responsible for correctly collecting and receiving the message.
You can use BytesBuilder class to collect and parse the messages.

Click to expand...

emexes said:

Maybe even today, if I can find a readable MODBUS format specification.

Click to expand...

embedded said:

i am out of home ...after coming back giving you feedback

Click to expand...