| Re: [hono-dev] CoAP protocol adapter for Hono |
In our case the device would then e.g. POST to the /telemetry resource on the CoAP protocol adapter
On Thu, 2018-03-22 at 13:36 +0100, Alfusainey Jallow wrote:
> Hi Kai,
>
> Am trying to think about the CoAP observe option and how that is suppose to
> work with a protocol adapter. my understanding is that devices only publish
> data (telemetry and events) to be consumed on the other side, right? Its more
> like a one-way traffic (from devices to hono then downstream).
>
> if that is the case, then IMHO, devices should not register an interest to
> observe state-changes for specific resources. the reason is that even if the
> state of a resource should change, its not the devices that should be notified
> about the changes but rather the consumer applications. is that correct?
>
The devices will _never_ observe resources on the cloud (Hono) side. If at all,
the protocol adapter will observe resources on the devices. However, it is
questionable if the whole Observe mechanism is actually suitable for long term
observations of resources because of its problems with NAT traversal.
The Californium folks instead propose to have the CoAP client (the protocol
adapter in this case) executing a resource on the CoAP server (the device) in
order to instruct it to start reporting the value of the resource of interest by
means of a CoAP POST or PUT. In our case the device would then e.g. POST to the
/telemetry resource on the CoAP protocol adapter.
> kind regards
>
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