MQTT client/broker on small embedded systems (MQX?)

[john]

I'm considering using MQTT in an upcoming project, but the target hardware is pretty small, 512K flash, 64K SRAM.  That rules out Linux, so I'd be porting to MQX, which has an almost-sockets Ethernet library and a not-nearly pthreads task/mutex library (IMHO).   I can see some benefits if I can get just a client working, but the big payoff is if I could get a broker working too.   

I'm looking for a basic "you're crazy" / "yeah, sure" / "maybe" response, and pointers to the best "C" sources for something so small.  

John

[Raphael Cohn]

John,

I've seen MQ clients run in such constraints very successfully, with TLS working effectively as a bonus. For a broker, it may be possible to use some of the protocol, although some features requiring unbounded state (will messages, QoS 2, retained messages) might be a bit tough to do. It really depends how much of the device's resources you need 'for other things'. For CANBUS integrations, I think you'd be screwed (from memory, the smallest I ever saw that could do useful things was about 44K, leaving you far too little). The sort of tricks I'd be thinking about are using the flash storage to include as much meta-data and state of topics, message transmission, etc, as possible, whether in file names, memory offsets, pointer bits, file attributes or simply headers which one can mmap (or the equivalent) or swap in. Maybe even to the point of storing messages as MQTT packets with a 'x remaining to read / write' header.

If it's useful I do know a freelance guy who's done this sort of thing before. Happy to put you in touch.

Raphael Cohn
Chief Architect, stormmq

Co-Chair, OASIS MQTT Standard

Secretary, OASIS AMQP Standard
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[Dave Locke]

A client will easily run there - there are a number of examples of clients running on embedded systems such as the arm mbed environment.  There are some thoughts around modifying the paho mqtt c client to make it make it easier to target to embedded systems, today it relies on posix interfaces.  

With respect to server / broker support, with 64k ram that should be sufficient to run a small broker.  If memory serves me right RSMB runs in a couple of K and RSMB is a full feature MQTT server. That said not aware of a non posix based server.


All the best
Dave

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[Caio]

Good question

2013/11/21 john <r10kinds...@gmail.com>:

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Caio Pereira