How to connect using Websocket Api

Agents, Protocols and APIs
1

I have a device which is publishing to an attribute now I want to make connection with attribute to get data as soon as it is published. I want to make it realtime using websocket apis but I am unable to find how can I subscribe to attribute for realtime update?

2

There is some documentation on the GitHub wiki to get you started with listening to attribute updates;

3

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this part I am able to achieve but how to do next. I want to subscribe to building device attribute city then how to send here?

wss://localhost:8080/websocket/events?Realm=smartcity&Authorization=Bearer%20eye2238f3a-e43c-3f54-a05a-dd2e4bd4631f&asset=building1&attribute=city

Also, will it be same for publish?

4

You can only subscribe to attribute events once authenticated.
The URL you’re talking about is to instantiate the connection by authenticating.

So;

  1. Use wss://localhost:8080/websocket/events?Realm=smartcity&Authorization=Bearer%20eye2238f3a-e43c-3f54-a05a-dd2e4bd4631f to connect and authenticate with the WebSocket API
  2. Send a JSON message using the EventSubscription format; (as written in the docs)
    For example, to subscribe to a single attribute;
SUBSCRIBE:{"eventType": "attribute", "filter": { "ref": { "id": "<asset id>", "name": "<attribute name>" }}

(can’t verify this, and I’m not 100% familiar with the WS API, so check docs if not working)

  1. You’ll get a message prefixed with SUBSCRIBED: or an error verifying the subscription.

.
It sadly involves quite a bit of diving into the JavaDoc, same counts for publishing.
We should write some documentation on this. :sweat_smile: