Managing two simultaneous Winsock connections

[Stile]

ve buillt an app which establishes 2 winsock connections simultaneously. The IP for both sockets is the same, but ports are different.

With Winsock1 
.RemoteHost = "255.255.255.255" 
.RemotePort = 1002 
.Bind 1001 
End With 

With Winsock2 
.RemoteHost = "255.255.255.255" 
.RemotePort = 1004 
.Bind 1003 
End With

I receive a data stream on both the IPs, which I then parse and display in my application. The data coming in is received by Databyarrival method. It works fine for the most part. However, there are certain instances, where one of the broadcasts freezes up, while the other is still running.

Any idea why one broadcast may freeze up randomly, and what can be done to avoid this?

[Doogle]

There's a million and one possible reasons. Could you post the code for the DataArrival events please - that's normally the most problematic area.

[Stile]

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)
    
    Dim strData As String
   
    Winsock1.GetData strData
    strfield0 = vbNullString
 

'The following code parses the datafeed that I receive on the port.
   
    For x = 1 To 10 Step 1: strfield(x) = vbNullString: Next x
    For x = 1 To 24 Step 1: strfield1(x) = vbNullString: Next x
    
    For x = 1 To Len(strData) Step 1
        chrchk = Mid(strData, x, 1)
        If chrchk <> "~" Then strfield0 = strfield0 & chrchk
    Next x
    

   y = 1
    For x = 1 To Len(strfield0) Step 1
        chrchk = Mid(strfield0, x, 1)
        If chrchk <> "|" Then
            strfield(y) = strfield(y) & chrchk
        ElseIf chrchk = "|" Then
            y = y + 1
        End If
    Next x
    
    y = 1
    For x = 1 To Len(strfield(9)) Step 1
        chrchk = Mid(strfield(9), x, 1)
        If chrchk <> ";" Then
            strfield1(y) = strfield1(y) & chrchk
        ElseIf chrchk = ";" Then
            y = y + 1
        End If
    Next x
        
    y = 1
    For z = 1 To 10 Step 1
        ucasestr(z) = UCase(txtSymbol(z).Text)
        If strfield1(2) = ucasestr(z) And strfield(7) = "?REGCO.?." Then
            txtPrice11(z).Text = strfield1(6): txtVolume11(z).Text = strfield1(5)
            txtPrice22(z).Text = strfield1(7): txtVolume22(z).Text = strfield1(8)
        End If
    Next z
    
    For z = 1 To 10 Step 1
        If txtPrice11(z).Text <> "" And txtPrice2(z).Text <> "" Then
            DiffPriceIP = Val(txtPrice11(z).Text) - Val(txtPrice2(z).Text)    
            txtPriceDiffIP(z).Text = DiffPriceIP
        End If
    Next z
    
    strData = vbNullString

End Sub

And the second is....

Private Sub Winsock2_DataArrival(ByVal bytesTotal As Long)
    Dim strData4011 As String
    Dim array4011(1 To 21) As String
    Dim array4011a(1 To 11) As String
    
    Winsock2.GetData strData4011

'The following is to parse the stream that i receive.

    For a = 1 To 21
    array4011(a) = vbNullString
    Next
    
    For a = 1 To 11
    array4011a(a) = vbNullString
    Next
    
    b = 1
    For a = 1 To Len(strData4011)
        ChrChk4011 = Mid(strData4011, a, 1)
        
        If ChrChk4011 <> ";" Then
            array4011(b) = array4011(b) & ChrChk4011
        ElseIf ChrChk4011 = ";" Then
            If b < 10 Then b = b + 1
        End If
    Next

    For a = 1 To Len(array4011(1))
        ChrChk4011 = Mid(array4011(1), a, 1)
        
        If ChrChk4011 <> "|" Then
            SymbolParse = SymbolParse & ChrChk4011
        ElseIf ChrChk4011 = "|" Then
            Exit For
        End If
    Next

    If SymbolParse = "@@PLAIN_UDP@@FEED" Then
        For a = Len(array4011(1)) To 1 Step -1
            ChrChk4011 = Mid(array4011(1), a, 1)
            
            If ChrChk4011 <> "|" Then
                Symbol4011 = Symbol4011 & ChrChk4011
            ElseIf ChrChk4011 = "|" Then
                Exit For
            End If
        Next a
    End If

    Symbol4011 = StrReverse(Symbol4011)

    For a = 1 To 10
        If txtSymbol(a).Text = Symbol4011 And array4011(2) = "T-REG" Then
            txtPrice1(a).Text = Val(array4011(6))
            txtPrice2(a).Text = Val(array4011(7))
        End If
        If txtPrice1(a).Text <> "" And txtPrice22(a).Text <> "" Then
            DiffPrice = Val(txtPrice1(a).Text) - Val(txtPrice22(a).Text)
            txtPriceDiff(a).Text = DiffPrice
        End If
        
    Next a
    
    strData4011 = vbNullString

End Sub

Whats noteworthy is that if i run one socket connection at a time, it never freezes. But if i run both in the same application, Winsock1 freezes randomly....but Winsock2 does not freeze.
Any help?
Thanks

[Doogle]

Well, to start with, you don't seem to have an Application Protocol. In your DataArrival events how do you know when you've received a complete record? A common misapprehension is that if I issue a SendData it will generate a DataArrival event at the other end. That is not necessarily true. A SendData may or may not generate one or more DataArrival events. Uisng TCP and IP the only assumption you can make is that all the data will eventually arrive (or an error will be raised) and the data will arrive in the same order in which it was sent. You have to perform Buffer Management in your code to cater for all situations.

What are the symptoms of "freezing"!? Is Winsock1 busier than Winsock2?

[Stile]

Being a novice, i only know so far as to receive data through the getdata component. Each batch of data that i receive is separated by a line separator, which i assume tells the app that one complete record has arrived. And that seems to be true when i run only one of these 2 at a time. But it is only when I run them both in the same application simultaneously, that this freeze occurs.

Yes, winsock1 is busier than winsock2. Both are UDP ports.
What is application protocol, and how do i perform buffer management in this case? sorry for the primitive queries, but im a beginner at this. Thanks.

[Doogle]

Ok, you might like to read Post#5 of this thread http://www.vbforums.com/showthread.php?t=502379 (to save me typing it all in again)

Is there any particular reason you're using UDP as opposed to TCP? UDP is not a 'reliable' protocol, in other words if packets go astray the protocol doesn't care or report the fact, whereas TCP is a 'reliable' protocol and delivery is guaranteed (or an error is raised)

[Stile]

I am using UDP because that is the protocol on which the data is coming in, so I guess i have no other choice. Or do ? Is it possible for me to use TCP while the incoming data is using UDP?
Ive given your post a read, and am trying to understand it. Thanks for the reference. In the meantime, if you have any ideas regarding this code above, do let me know.

Thanks again.

[Doogle]

Ok.I'll take a further look...

[opus]

Hi Style,
it sounds as if you don't have the control over the format of the data that is coming in. So you can't change anything on the sending side ( and you are stuck with UDP).
It looks to me as if you might be getting several messages in during a single run of the dataArrival sub. Don't you get anything for a ending sign of a message?, because that would help to seperate the messages (which might be both in your strData!
Have a look along this way!

[Doogle]

OK, in Post #5 you mention a 'line separator'. Assuming that is a vbNewLine then the following will provide you with some buffer management.(Winsock1)

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)
    
    Dim strData As String
    Static strBuffer As String
    Dim lngPos As Long
    Dim boFinished As Boolean
    
    Winsock1.GetData strData
    strBuffer = strBuffer & strData
    Do
        lngPos = InStr(strBuffer, vbNewLine)
        If lngPos > 0 Then
            '
            ' There's at least 1 complete record in the buffer
            ' unblock it and process it
            '
            strdata = Mid$(strBuffer,1,lngpos)
            strfield0 = vbNullString
 

            'The following code parses the datafeed that I receive on the port.
   
            For x = 1 To 10 Step 1: strfield(x) = vbNullString: Next x
            For x = 1 To 24 Step 1: strfield1(x) = vbNullString: Next x
    
            For x = 1 To Len(strData) Step 1
                chrchk = Mid(strData, x, 1)
                If chrchk <> "~" Then strfield0 = strfield0 & chrchk
            Next x
    

            y = 1
            For x = 1 To Len(strfield0) Step 1
                chrchk = Mid(strfield0, x, 1)
                If chrchk <> "|" Then
                    strfield(y) = strfield(y) & chrchk
                ElseIf chrchk = "|" Then
                    y = y + 1
                End If
            Next x
    
            y = 1
            For x = 1 To Len(strfield(9)) Step 1
                chrchk = Mid(strfield(9), x, 1)
                If chrchk <> ";" Then
                    strfield1(y) = strfield1(y) & chrchk
                ElseIf chrchk = ";" Then
                    y = y + 1
                End If
            Next x
        
            y = 1
            For z = 1 To 10 Step 1
                ucasestr(z) = UCase(txtSymbol(z).Text)
                If strfield1(2) = ucasestr(z) And strfield(7) = "?REGCO.?." Then
                    txtPrice11(z).Text = strfield1(6): txtVolume11(z).Text = strfield1(5)
                    txtPrice22(z).Text = strfield1(7): txtVolume22(z).Text = strfield1(8)
                End If
            Next z
    
            For z = 1 To 10 Step 1
                If txtPrice11(z).Text <> "" And txtPrice2(z).Text <> "" Then
                    DiffPriceIP = Val(txtPrice11(z).Text) - Val(txtPrice2(z).Text)
                    txtPriceDiffIP(z).Text = DiffPriceIP
                End If
            Next z
            '
            ' Processing is complete for this record
            ' Now check if there's anything else in the Buffer
            '
            If lngPos < Len(strBuffer) Then
                '
                ' Yes there is, shift it to the front of the buffer
                ' and go round the loop again
                '
                strBuffer = Mid$(strBuffer, lngPos + 2)
            Else
                '
                ' Flush the buffer and signal to exit the loop
                '
                strBuffer = ""
                boFinished = True
            End If
        Else
            '
            ' Havent got a complete record yet so just exit
            '
            boFinished = True
        End If
    Loop Until boFinished = True
End Sub

If the 'Line separator' is just vbLf then make the following changes

lngPos = InStr(strBuffer, vbNewLine)
'
' change to 
'
lngPos = InStr(strBuffer, vbLf)
'
' and
' 
strBuffer = Mid$(strbuuffer, lngPos + 2)
'
' change to
'
strBuffer = Mid$(strBuffer, lngPos + 1)

There may be a few typos in the code I've added as it's not tested but hopefully you can see the logic.

[Stile]

Many thanks Doogle for your help. Im giving it a try as we speak. Will get back to you on it.

Just to mention, the line separator that is being used is the ~ sign. Is that the same as VBnewLine? pardon my ignorance.

[Doogle]

No, it's not the same. You'll need to make a couple of changes:

lngPos = InStr(strBuffer, vbNewLine)
'Change to
lngPos = InStr(strBuffer,"~")
'and
strBuffer = Mid$(strBuffer, lngPos + 2)
'change to
strBuffer = Mid$(strBuffer, lngPos + 1)

[Stile]

Thanks a million

[Doogle]

My pleasure

If it's working ok with Winock1 I suggest you put the same logic into the Winsock2 DataArrival event.