VB6 - Proper sending/receiving data with Winsock (tutorial & code)

[DigiRev]

I think this is information every Winsock or client/server developer should know. It is something I wish I had figured out soon after I first started. While it has been common knowledge to me for some time now (and for many others), without it, your client/server programs will be very fragile and bugs can pop up at any time.

The tutorial is meant to be as short and straightforward as possible. I wrote this in about an hour or maybe a little more.

Please let me know if it's helped, if you have any questions, if there's a bug, or anything. And read the tutorial before looking at the code.

This article explains (and gives code for) how to handle 2 or more packets arriving at the same time, or "together". But unlike other tutorials, it also explains another critical problem, which is one packet getting split in the middle. So I think even if you know most (or possibly all) of this stuff it is still useful information.

[itzviper]

Hey i'd like to start out by saying nice example. Very easy to follow. I havn't tested it fully yet, but I was looking through the code for the byte arrays code that you included. I'm looking in the DataArrival on the server winsock control.

Private Sub sckServer_DataArrival(ByVal bytesTotal As Long)
    Dim bytData() As Byte, lonLoop As Long
    Dim lonUB As Long, bytCheck() As Byte
    Dim lonPrevEOP As Long, bytPacket() As Byte
    Dim bytTemp() As Byte, bytTruncated() As Byte
    Dim bolTruncated As Boolean, lonLastPos As Long
    Dim bytHeader() As Byte, strHeader As String
    
    'Get received data and put it into bytData().
    sckServer.GetData bytData(), vbByte + vbArray, bytesTotal
    
    Debug.Print StrConv(bytData, vbUnicode)
    
    'Append data to buffer.
    'Byte_Append bytBuffer, bytData

You have the Byte_Append bytBuffer, bytData commented out. This will effectively elimenate the buffer. Is this a mistake? or am i just reading it wrong? Again i havn't had time to check it i was just reading through.

[DigiRev]

Hey i'd like to start out by saying nice example. Very easy to follow. I havn't tested it fully yet, but I was looking through the code for the byte arrays code that you included. I'm looking in the DataArrival on the server winsock control.

Private Sub sckServer_DataArrival(ByVal bytesTotal As Long)
    Dim bytData() As Byte, lonLoop As Long
    Dim lonUB As Long, bytCheck() As Byte
    Dim lonPrevEOP As Long, bytPacket() As Byte
    Dim bytTemp() As Byte, bytTruncated() As Byte
    Dim bolTruncated As Boolean, lonLastPos As Long
    Dim bytHeader() As Byte, strHeader As String
    
    'Get received data and put it into bytData().
    sckServer.GetData bytData(), vbByte + vbArray, bytesTotal
    
    Debug.Print StrConv(bytData, vbUnicode)
    
    'Append data to buffer.
    'Byte_Append bytBuffer, bytData

You have the Byte_Append bytBuffer, bytData commented out. This will effectively elimenate the buffer. Is this a mistake? or am i just reading it wrong? Again i havn't had time to check it i was just reading through.

Wow, what a terrible mistake. Thanks for pointing that out, yes that should not be commented.

[pannam]

hey digiRev thank you for the code i was using your project byte array and i removed the comment on

Byte_Append bytBuffer, bytData

..yet, i get error on your code on local error handling ..

 Private Function SafeUBByte(ByteArray() As Byte) As Long
    On Error GoTo ErrorHandler
    
    SafeUBByte = UBound(ByteArray()) + 1 'error
    
    Exit Function
    
ErrorHandler:
    SafeUBByte = 0
    
    Exit Function
    
End Function

lastly thank you very much ..i was indeed in search of this you rock

[coolcurrent4u]

so what would the corrected code be now.
can u please attache the corrected version

[VbNetMatrix]

so what would the corrected code be now.
can u please attache the corrected version

I know... probably dead thread... but for thoses who are looking at the solution TODAY, like I am...

I don't think the line should be commented out...

The lines:

    'Append data to buffer.
    'Byte_Append bytBuffer, bytData

are there for documentation purpose. it say: 'This is how it is done!"

further below in the code of sckServer_DataArrival, you got 3 times the same line but for different data arrival method.

thoses are the real lines.


The author can correct me if I'm wrong.