Re: TCP server stop receiving new connections

What do you do in your OnAccept handler? In particular,
do you try to accept multiple sockets? A test to try is to
reset the event mask of your listening socket each time you
exit its OnAccept handler.

Also, as a reality check - make sure your message loop
never gets stuck... E.g. when you break into the debugger,
almost always you should end up in the message loop.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Julián Rodríguez Bajo" <julian.rodriguez@xxxxxxxxxx> wrote in message
news:ecZt4s6wHHA.1776@xxxxxxxxxxxxxxxxxxxxxxx
History continues bellow...

Julián Rodríguez Bajo escribió:
Ali escribió:
On Jul 10, 4:34 pm, Julián Rodríguez Bajo
<julian.rodrig...@xxxxxxxxxx> wrote:
Ali escribió:



On Jul 9, 1:06 am, Julián Rodríguez Bajo <julian.rodrig...@xxxxxxxxxx>
wrote:
Hi folks.
I have a strange problem in my class library used by all our client
and
server applications.
There are servers listening on different ports for different
purposes.
Sometimes (when a lot of new clients try to connect to the same
server),
one of the servers (not allways the same one) stops accepting new
incomming connections, but keeps current connections. Server port
appears as LISTENING, but OnAccept never arrives to server. New
client
connections receive a WSAECONNREFUSED error. In this situation, if I
call Accept directly in a test application, one incomming connection
is
accepted, but no messages can be sent cliet -> server nor server ->
client, and after 15 seconds connection is dropped because of a
custom
keep alive mechanism. Running server and a lot of client applications
in
same machine fails the same way.
Both client and server processes use the same class library. The
library
is a statically linked MFC based static library. Both classes, server
and client, derive from CAsyncSocket. There are no threads involved.
I have tried changing nConnectionBacklog parameter to Listen, but
that
does not seems to make any effect.
Any suggestion would be apreciated.
Best regards.
--snip--
Both classes, server and client, derive from CAsyncSocket. There are
no threads involved.
If you are not using threads fro non-blocked sockets then how you
honour the requests from multiple clients?
ali
When a CAsyncSocket derived socket is created, by default a
WSAAsyncSelect is called with FD_READ | FD_WRITE | FD_OOB | FD_ACCEPT |
FD_CONNECT | FD_CLOSE event notification mask. Every socket
notification
is received in an WM_SOCKET_NOTIFY message. MFC dispatches every socket
notification to the corresponding virtual method of the CAsyncSocket
object:

* FD_READ --> Calls OnReceive function.
* FD_WRITE --> Calls OnSend function.
* FD_OOB --> Calls OnOutOfBandData function.
* FD_ACCEPT --> Calls OnAccept function.
* FD_CONNECT --> Calls OnConnect function.
* FD_CLOSE --> Calls OnClose function.

So, there is no need to use multiple threads to serve multiple clients.

Hmm, sounds good to me. Your architecture looks good and quite natural
BUT it seems you need to tweak with your MFC message pump. Anyway, you
can write a simple hook for WM_SOCKET_NOTIFY message to double check
your network part interface.


ali


ali



Good idea Ali. I would hook WM_SOCKET_NOTIFY to see what is going on.
Maybe WM_SOCKET_NOTIFY messages are received but not delivered correctly
by MFC framework.

Thanks for your suggestion.



After some testing, problem seems that CSocketWnd::OnSocketNotify is never
called. CSocketWnd::OnSocketNotify calls CSocket::ProcessAuxQueue, wich
calls CAsyncSocket::DoCallBack wich calls the corresponding callback
function of the CAsyncSocket object:

CSocketWnd::OnSocketNotify -->
CSocket::PRocessAuxQueue -->
CAsyncSocket::DoCallBack -->
CAsyncSocket::On[Send|OutOfBandData|Accept|Connect|Close]

In file sockcore.cpp @ line 1140:

BEGIN_MESSAGE_MAP(CSocketWnd, CWnd)
//{{AFX_MSG_MAP(CWnd)
ON_MESSAGE(WM_SOCKET_NOTIFY, OnSocketNotify)
ON_MESSAGE(WM_SOCKET_DEAD, OnSocketDead)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

So, OnSocketNotify must be called for every WM_SOCKET_NOTIFY received by
the CSocketWnd, but as stated above, connecting around 50 clients
concurrently to my server, OnSocketNotify is never called. Even if I
accept "manually" an incomming connection, my server does not receives
FD_READ from clients.



.

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