Question about possible bug in send logic about mqtt-c

[LiamBindle]

Hi Andrew, thanks for opening the issue. You bring up a good point—I don't think partially sent messages are continued properly by subsequent mqtt_sync() calls.

Partially sent messages

That being said, I don't think I'd consider this a bug, just because MQTT-C doesn't claim to support such a feature. The mqtt_pal_sendall() function is supposed to send everything in the send buffer, otherwise return an error.

That being said, I think this would be a good feature! And I'd be more than happy to merge a PR with this feature if you're interested in implementing it!

The PAL

Regarding the PAL, the PAL is intentionally simple. The PAL in mqtt_pal.c is meant to be used as a starting point for porting/improving to make your own PAL, so it's meant to be as simple and easy to understand as possible.

A conditional that checks EWOULDBLOCK/EAGAIN to continue the while loop rather than return a socket error would be a good update though, and I'd be happy to merge a PR!

[andrewchambers]

Thanks for the reply, I think I had assumed the code was meant to work with non blocking sockets, but I can see that was just an assumption on my part.

I imagine not too much is needed to implement such a feature, but I don't have a need as in the end I used redis pubsub instead of mqtt.

thanks again for the answer though. This is a great project.

[LiamBindle]

Fair enough. Thanks for bringing this to my attention.

Cheers,

Liam