Re: Problems with CAsyncSocket::Receive

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Wed, 23 Aug 2006 10:23:28 -0400
TonyG wrote:

I'm having problems with my CAsyncSocket derived class. I'm using TCP and
the problem manifests itself on the client side. Sometimes my OnReceive will
get called and when my handler calls Receive, will return with a zero return

Microsoft help states "If the connection has been closed, it returns 0."

When this happens, what should I do? Is there cleanup I should do?

I've tried calling CAsyncSocket::Close. My code then waits 5 seconds and
then attempts to reconnect. It seems to get into a funny state and all
communications grinds to a halt.

What should I do?

If you call Receive and request less data than the socket has available
it will immediately queue another OnReceive notification message. But
if you also call Receive a second time and take all available data, the
queued notification can become an OnReceive that yields a zero return.
So don't call Receive more than once within OnReceive. Do nothing if
Receive returns 0.

To overcome the reconnect delay (the socket is "stale"), create your
socket object dynamically ('new' before Create, 'delete' after OnClose),
and pass 0 as the first parameter of the socket Create call (so your
reconnect will use a different local port number at your end).

Scott McPhillips [VC++ MVP]

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