I think it was done intentionally,
when socket closed , it signals that data available, to awake process
which waiting for data. Then, when process tries to read it, it
returns 0 bytes.

I think it's same as with socket's read() function.
If remote side closed gracefully, a blocking read() function returns
with 0, indicating that there 0 bytes read, and connection is closed.

On 25/02/2008, Klaus D. Witzel <klaus.witzel at cobss.com> wrote:
> I'm trying to provoke the Exceptions which Socket>>#waitForDataFor: would
>  signal on failure (and test that it does so), to no avail (no, the .image
>  isn't locked and the process doesn't hang).
>
>  The below runs in both the Squeak 3.9,3.8 final .images with both the
>  3.10.2,3.10.6 VMs on win32; the worker process always terminates without
>  an exception.
>
>  The implementation of #waitForDataFor:
>  (#waitForDataFor:ifClosed:ifTimedOut:) looks like #dataAvailable returns
>  true but there cannot be any data since nothing was ever sent. *but* after
>  closing the client side, the other side's #dataAvailable
>  (#primSocketReceiveDataAvailable) returns true ...
>
>  Any hint(s) on what's going on (or wrong) will be recognized with
>  gratitude.
>
>  /Klaus
>
>   | localhost serverSocket sessionSocket clientSocket worker |
>
>   localhost := NetNameResolver localHostAddress.
>  "warning:" Socket allInstancesDo: [:socket | socket destroy].
>   serverSocket := Socket newTCP listenOn: 7680 backlogSize: 1.
>   clientSocket := Socket newTCP connectNonBlockingTo: localhost port: 7680.
>   sessionSocket := serverSocket waitForAcceptFor: 1.
>   worker := [sessionSocket waitForDataFor: 1] fork.
>   Processor yield.
>   Transcript cr; show: serverSocket statusString, ' [server]';
>         cr; show: clientSocket statusString, ' [client]';
>         cr; show: sessionSocket statusString, ' [session], dataAvailable: '
>                 , sessionSocket dataAvailable storeString;
>         cr; show: 'worker: ', worker browserPrintString.
>   [clientSocket close] on: Exception do: [:ex|].
>   Processor yield.
>   Transcript cr; show: serverSocket statusString, ' [server]';
>         cr; show: clientSocket statusString, ' [client]';
>         cr; show: sessionSocket statusString, ' [session], dataAvailable: '
>                 , sessionSocket dataAvailable storeString;
>         cr; show: 'worker: ', worker browserPrintString; cr.
>   [sessionSocket destroy] on: Exception do: [:ex|].
>   [clientSocket destroy] on: Exception do: [:ex|].
>   [serverSocket destroy] on: Exception do: [:ex|]
>
>
>


-- 
Best regards,
Igor Stasenko AKA sig.