Re: [lwip-users] How to set callback for accepted netconn connection?

[address@hidden]

Am 22.11.2021 um 15:21 schrieb Grant Edwards:
> On 2021-11-22, goldsimon@gmx.de <goldsimon@gmx.de> wrote:
> > Am 19.11.2021 um 22:55 schrieb Grant Edwards:
> > > After accepting a tcp connection with netconn_accept(listenconn,
> > > &newconn), how does one set the callback function for newconn?
> >
> > The callback gets copied from the listening connection.
>
> I suspected that might be the case, but hadn't been able to find where
> that happened in the source code. For some reason I thought it had to
> be happening at the netconn layer, but now I see it happens in
> api_msg.c::accept_function()

Well, that file *is* one half the netconn layer (the half running in
tcpip_thrad, not in the application threads).

Regards,
Simon

> > While it would probably not be a big problem to change the
> > netconn->callback member at that point, it's not currently
> > implemented.
>
> There's no real need to change it. I assume that if I ignore events on
> a netconn instance it can still be used in a normal blocking manner.
>
> > However, there would be a race condition: the callback may be called
> > right after accepting the underlying connection, but before an
> > application thread has pulled the new connection out of the
> > listener's acceptmbox. So there might be a time span where the
> > underlying TCP connection can receive data but you wouldn't have
> > changed the callback yet.
> >
> > Being like that, we live with having one callback for all types of
> > connections in the socket layer.
>
> There's nothing wrong with that, I just couldn't find any information
> on how to set up callbacks for netconn server sockets.
>
> --
> Grant
>
>
>
>
>
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