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Re: [paho-dev] MQTT-SN to MQTT Gateway


On Sat, 20 Feb 2016 at 06:12 Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hi Paul,

my plan is that the networking classes be replaceable, as they are for MQTTClient.  The intention is that networking classes can then be written for UDP, ZigBee or any suitable networking transport, even serial.

So, you are seeing this as more of a toolkit or framework, with integration with other components at the code level, rather then a service which would be integrated at the system level.

Do you have an intended scale in mind? If we keep the gateway super tight and constrained, I'd have some concerns with a lot of clients; for example, if I have a couple of hundred MQTTSN clients or more, and we run without threads or async calls, there could be quite a bit of data loss while we spin up TCP connections to the MQTT server (especially if TLS is used) as the MQTTSN clients will be blocked, and there is a fair chance they are using poorly buffered serial connections. Using async or threads would likely demand usage of dynamic memory usage or considerably more complexity.

Maybe two should target two gateway profiles: A "powerful" one intended run on something with lax constrains (lets say raspberry pi as the lower end) and a very constrained one, intended for fewer clients. 

Or maybe (as has been known to happen) I am worrying for nothing.

In any case, I'm certainly willing to run some testing.

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