MQTT with Iridium SBD

[daebarkee]

Hello,

I am trying to use mqtt with Iridium short burst data (SBD) which has a size limit in a message.

In this case, I need to touch transmission part of mqtt.

If mqtt uses TCP send(), I need to replace it with my own FragmentAndSend() which communicates with Iridium modem.

Do we have any previous trial like this?

Regards,

DBK.

[Hans Jespersen]

MQTT messages can be bigger than a single TCP packet so is the SBD limit really an MQTT message size limit or a TCP MTU size limit? If it is the later could you not just modify the MTU size to have MQTT send smaller TCP packets? 

[daebarkee]

I think this is about how to call a specific send() command of Iridium modem from MQTT library rather than a size issue. 

For example, from "channel.BasicPublish()" how can I let it call my Iridium Send() command???

[Hans Jespersen]

You didn't say what source code you are working with but channel.BasicPublish() is a RabbitMQ function name. I suggest you contact Pivotal or try a RabbitMQ alias.

MQTT runs over TCP/IP so it you are trying to remove the standard TCP transport and replace it with SBD over a serial port then it's not really the MQTT protocol any more.