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

[Greg Troxel <gdt@xxxxxxxxxx>]

Matthew Giassa <matthew@xxxxxxxxxx> writes:

> 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.

My first question would be if this is addressed in any standards; right
now mosquitto seems to implement an MQTT standard which should enable
bridging to a different implementation.  I'm guessing this is no
discussion of bridging over i2c or indeed over anything other than IP.

My immediate reaction is that the simplest path to solving this problem,
and especially related problems likely to arise over time, is to create
an IP over i2c implementation, perhaps modeled after SLIP or PPP, and
perhaps using actual SLIP or PPP over a serial port implemented over
i2c.  If you have full Unix on both sides, it should be enough to create
a virtual serial port and run ppp, and then let mosquitto bridge
naturally.

The IP over i2x approach also seems useful if you need communications
other than MQTT.