Winsock DataArrival problem

[mibosoft]

Hi,
I have integrated a winsock server in my app and works fine as long as complete data packages are received. The server is based on a famous example (I think):

http://fox.wikis.com/wc.dll?Wiki~WinSockOCXSample

The problem is how to determine that received data is complete. The wiki example solves it by adding a end-of-transmission sign in alla sent data. In the same way, received data isn't computed until the EOT sign is reached.

++++++++++++snip

PROCEDURE DataArrival
LPARAMETERS tnByteCount
LOCAL lcBuffer
lcBuffer = SPACE(tnByteCount)

* This gets the data from the socket. It can happen, that the data isn't
* received in a single rush. Thus we need a EOT (end of transmission)
* sign to be sure, the data is complete. Until we get this, the data
* is stuffed into cReceiveBuffer.

This.GetData( @lcBuffer, , tnByteCount )
IF AT( EOT, lcBuffer ) = 0 && Not yet finished
This.cReceiveBuffer = This.cReceiveBuffer + lcBuffer
ELSE
This.cReceiveBuffer = This.cReceiveBuffer + LEFT( lcBuffer, AT( EOT, lcBuffer ) -1 )

...

++++++++++++snip

The data I want to receive comes from a POST action in a web browser form. How can I determine (in the DataArrival event) that all data has been received? Any hints are welcome.

Thanks'
Micael

 

[DSummZZZ]

That's the thing about TCP/IP. You have basically three options:
Wait for an EOT character
Wait for a timeout period
Know in advance how long the message will be

The host's responsibility ends with receiving messages. There's nothing built into the protocol to tell it how long a message will be, only that the message it received got there in one piece. Different senders may have their output buffers set to different lengths.


-Dave Summers-

Even more Fox stuff at:

http://www.davesummers.net/foxprolinks.htm

 

[agoeddeke]

I always send the size of the message as the first 10 bytes of the message. Then you know what to wait for.

I would be careful using some sort of EOT character especially if you messages contain binary data.

Andy

 

[mibosoft]

Thanks' for your answers. What I do now is to check for a certain string, always present at the end of the message, before closing the connection. This seems to work fine.
/Micael