Winsock byte array - need crash course *resolved

[leinad31]

Here's the code that sends the data.

'This part is in another procedure
    Select Case Left(strData, 20)
    Case CM_QUERY_HOSTINFO
        strSendData = CM_QUERY_HOSTINFO
        Call SendData_sckTCP(SocketIndex, strSendData)
        
        MsgBox frmMainCommon.sckTCP(SocketIndex).State
        If IntVar.Flag_IsServer = True Then
            strSendData = CM_INFO_SERVERINFO & HostInfo_Local.B_UCDHostname
            Call SendData_sckTCP(SocketIndex, strSendData)
        Else
            strSendData = CM_INFO_LOCALINFO & HostInfo_Local.B_UCDHostname
            Call SendData_sckTCP(SocketIndex, strSendData)
        End If
 
 
'This the generic send procedure
Public Sub SendData_sckTCP(SocketIndex As Integer, strSendData As String)
'Procedure Description:
'
 
    Dim Counter_SendAttempts As Byte
    Dim strIPAddress_tmp As String
    
    Counter_SendAttempts = 0
    strIPAddress_tmp = ""
    
On Error GoTo Error_Handler 'Enable error handler
    frmMainCommon.sckTCP(SocketIndex).SendData strSendData
 
On Error GoTo 0             'Disable error handler
    Exit Sub                'Exit function on successful send.
 
Error_Handler:
    Counter_SendAttempts = Counter_SendAttempts + 1
    If Counter_SendAttempts = MaxRetry_Send Then
        
        strIPAddress_tmp = IndexToIP_HostInfo_Array(SocketIndex)
        MsgBox "Unable to send data to remotehost " & Trim(strIPAddress_tmp) & "." _
            & vbCrLf & vbCrLf _
            & "sckTCP(" & SocketIndex & ") will be unloaded and the corresponding" _
            & vbCrLf & "host information will be removed from:" & vbCrLf _
            & "     HostInfo_Array()" & vbCrLf _
            & "     LoadedsckTCP_Array()", _
            vbOKOnly, "Error: SendData_sckTCP(" & SocketIndex & ")"
            
        Call UnassignIndex_sckTCP(SocketIndex)
        Call RemoveFrom_HostInfo_Array(strIPAddress_tmp)
        
        Resume Next
    Else
        Resume  'Retry send.
    End If
    
'Procedure Analysis:
End Sub

Instead of two data arrivals (which I had expected to happen);

"CM_QUERY_HOSTINFO "
"CM_INFO_SERVERINFO UC-Daisy "

I got "CM_QUERY_HOSTINFO CM_INFO_SERVERINFO UC-Daisy "

WHERE DID I GO WRONG! *sniff

Is there anyway to make it two data arrivals? I want to avoid dealing with a stream as much as possible.

Because if I do, I have to check amount of bytes before send, send that info along with the packet, parse the stream at the other end according to this, and so on and so forth... *sniff

Can I use SendComplete in the solution, if so how?

[leinad31]

UnassignIndex_sckTCP(SocketIndex) essentially unloads the instance of the socket and updates UnloadedsckTCP_Array(). I keep track of the indexes I already used for reuse.

RemoveFrom_HostInfo_Array(strIPAddress_tmp) updates the array where I keep the info on the remotehost.

I don't think they have anything to do with the problem. Just in case your wondering.

[CVMichael]

Well, believe it or not, that is how a socket works...

The data that you send is a data stream, and if you send data at very short invervals, most of the data will be concatenated.

You will have to set some logic in your program to split the data, for example put your message in [] like "[message]", then you will know where a message starts and where it ends...

The way I do it is I send the length of how much is to send, something like "10:asdfghjklp", so then the program on the receiving side, it know how much data to expect, and if you send a lot of data like "100000:sdfsdfaf... etc" then the client can buffer all data until it gets 100000 bytes, then it will use the data...

[leinad31]

I was doing some research while waiting for a reply and I realized so... Oh well.

So what's the best approach? I was already considering making a trailer to complement the header. But it opens a can of worms if the user sends a message containing the header and/or trailer info.

Same with bytes total. What if they type "100000:sdfsdfaf" into the message. It will screw up the parser unless I make the parser very complex.

Is it possible to send a structure instead of a plain string?

[leinad31]

I think I've figured out a way to ignore the data/user message when parsing. Wish me luck

[CVMichael]

Good luck

But...
Even if the user types something like "5:12345", your program will send: "7:5:12345"

all you have to do is to get the number from the first ":" and read the given length as the message
So
it will read the length 7, and then it will take the next 7 characters as the message 5:12345

So it works always, it does not matter what they type because your number will always be first...

[leinad31]

I'll go with that. But I also plan to implement file transfer in the same connection. Since I'm using a generic send procedure I'll need to convert everything into a bit array. While I figure out the general design of the parser and anything else I have to redesign, can you give me a crash course on bit arrays in relation to winsock?

Major points would be:
- Is a character 8 bits, 16 bits, or OS dependent (the thought gives me a headache)?
- Converting a string to byte array, and vice versa.
- With your header suggestion, do I count total bytes or bits?
- Related to the above, when I load a file, its in chunks of 1 byte, right (haven't coded it yet)?
- And some other important pointers on bit array manipulation.

[CVMichael]

How to open and read the data from the file (can be any file type, even binary)

dim Buffer as string
 
open "myfile.dat" for binary access read lock write as #1
    buffer = String(lof(1), 0)
    Get #1, , buffer
Close #1

Now the thing is, when you send large amounts of data (over 1KByte), you need to break it down into smaller chunks

So... you have to send 1K, then wait until the data is sent, then send the other 1k and so on...

the hard part is that you cannot do this in one function since you have to do all the waiting...

first make a function that openes a file and sends the first 1K
then in the winsock1_SendComplete event you have to send the other 1K...

now there is another problem

You cannot do "winsock1.SendData myData" inside the SendComplete event.... winsock will give you and error because the sendcomplete function HAS to end it code, then you have to send the data

now, the only option is a timer set to interval of 1 (1 millisecond)

so...
here's the pseudocode...

add a timer on the form with interval = 1 and enabled = false

' globals
const bufflen as long = 1024
dim filenumber as integer
 
 
' open file and send 1K
private sub SendFile(byval myFile as string)
dim buffer as string
 
filenumber = freefile
open myFile for binary access read lock write as filenumber
buffer = string(bufflen, 0)
get filenumber, , lof(filenumber) & ":" & buffer
Winsock1.Send buffer
 
end sub
 
 
 
private sub winsock1_SendComplete()
   ' start the timer to send the next 1K
   timer1.interval = 1
   timer1.enabled = false
   timer1.enabled = true
end sub
 
 
 
private sub timer1_timer()
dim buffer as string
 
if loc(filenumber) + bufflen > lof(filenumber) then
   ' this is the last packet
   buffer = string(lof(filenumber) - loc(filenumber), 0)
else
   bufer = string(bufflen, 0)
endif
 
get filenumber, , buffer
winsock1.senddata buffer
 
if len(buffer) < bufflen or loc(filenumber) >= lof(filenumber) then
   ' close the file if no more data to send
   close filename
endf
 
' ALWAYS set it to false, because if not, it will send the next 1K
' without waiting until the current packet is sent
timer1.enambled = false
end sub

hope this helps...