Re: [lwip-users] Issues with netconn callbacks

[address@hidden]

Am 02.12.2019 um 20:39 schrieb Davide Bettio:
> Hello,
>
> I'm the author of AtomVM (https://github.com/bettio/AtomVM) and we are
> using lwip on ESP32.

So you're running the stock lwIP that comes with ESP32? If so, I don't
know how "vanilla" this is and how they keep their copy of lwIP up to
date...

> We decided to use netconn API since it provides us asynchronous callbacks.
> However I'm experiencing an unexpected behavior with it (when using it
> as a TCP server):
> I get my callback called also for netconns which I didn't accept yet.

I'm not sure I understand that. Just for you to know: netconn is the
basis of the standard socket implementation in lwIP but otherwise not
may not too be widely used.

Being like that, you *may* get problems when using netconn in a
different way than the socket API uses it internally. Maybe you can
cross-check your code against sockets.c and see if you do anything
different?

> So I get this output from my code:
>
> handler not found for: 0x3ffc3bf4
> processed all events
> found handler for: 0x3ffcd464
> tcp_server_handler
> going to send a ready message
> accepted conn: 0x3ffc3bf4
> accepted_socket
>
> Is this an intended behavior?

That's no debug output from lwIP

> Also I have further questions about the netconn API:
>
> - Is it possible to check if any byte is already in the buffer ready to
> be received?

Yes, you can use nonblocking receive. Again, see sockets.c if you need
an example.

> - Is it possible to check if a netconn is still open or it has been closed?

Well, you get informed it is closed and you'll get an error trying to
use it...

Regards,
Simon