Re: [lwip-users] Can you connect a MQTT client directly from a PPPoS status callback?

[address@hidden]

Am 16.05.2019 um 18:31 schrieb Freddie Chopin:
> Hello Devanand!
>
> On Thu, 2019-05-16 at 20:41 +0530, Devanand Biradar wrote:
> > I have connected to mosquito cloud using Lwip via MQTT.
> > Using PPPOS with GSM module.
>
> Yes, I know this can be done, because I already have done it and it
> works (; But now I would like to make it more error-proof and
> responsive - my code so far is just a dirty proof-of-concept using
> stupid things like global flags and polling.
>
> So what I'm asking is this - is it safe to have code like this:

It's probably not safe as you risk calling back into modules that are
not reentrant. I don't know this for sure, just as a saftey measurement...

Maybe you could use tcpip_trycallback() from that callback?

Regards,
Simon

> // this function is registered via pppapi_pppos_create(...)
> // it is executed from within lwIP's TCP/IP thread
> void pppLinkStatus(ppp_pcb* pcb, int errorCode, void* context)
> {
>    if (errorCode == PPPERR_NONE) // PPP is connected successfully?
>      mqtt_client_connect(...);
>    else // PPP connection is lost
>      mqtt_client_disconnect(...);
> }
>
> The alternative is - for example - to call mqtt_client_connect(...)
> until it succeeds (including the last phase done in the MQTT's connect
> callback) periodically, for example every 10 seconds. However - if
> possible - I would prefer the first version, more "event based" and not
> requiring a thread that would have to monitor that.
>
> Regards,
> FCh
>
>
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