Re: [mosquitto-dev] Question: Plugins for bridging over arbitrary interf

[Matthew Giassa <matthew@xxxxxxxxxx>]

Good day,

Does the Mosquitto broker/service support plugins, or have any
minimal-working test examples to enable bridging two brokers over an
arbitrary interface?

In short, I have an embedded system that consists of various boards
(mostly Raspberry Pi3 and CubieTruck units) that use Mosquitto bridges
to broadcast system-wide changes to various pieces of hardware. One
design constraint (which cannot be avoided) is that two such boards are
only able to communicate with each other via an I2C link. The project
would benefit greatly from being able to make data from this isolated
board available to the rest of the system.

To the original question, are there any guides (i.e. how to write a
plugin if supported by Mosquitto, or a minimal API that must be
implemented, or existing code snippets for this purpose) that I could
use to "hit the ground running" and implement an
MQTT-over-custom-I2C-driver service/library to allow bridging of brokers
over arbitrary interfaces? I'd like to avoid "re-inventing the wheel" if
this is a common problem that has already been solved.

If this is not available/practical, then I guess my next step would be
to see which TCP-over-protocol-xyz implementations are available, if
any, for my current use case.

Additionally, does the `message_size_limit` option impact the size of
messages sent between brokers? If so, do the bridged brokers
automatically break-up and serialize messages if they are too big (i.e.
larger than `message_size_limit`)?

Thank you for your time and assistance.