Subscribing to topics

Prerequisites

You must have a WebSocket secure connection to the switch.
Access to the switch REST API must be enabled. The REST API access mode can be either read-only or read/write.

Procedure

Using the WebSocket secure connection, send a subscribe message that contains the topics to which you want to subscribe and a poll interval hint, if any:

For example:

{
  "type": "subscribe",
  "topics": [
    {
      "name": "/rest/v1/system/vrfs"
    },
    {
      "name": "/rest/v1/system/bridge/vlans/DEFAULT_VLAN_1?attributes=admin,oper_state_reason"
    }
  ],
  "hint": 5
}

If the subscriber already has a subscription to the specified topic, the following error is returned:
```
{
  "type":"error",
  "message":"The topic or combination of topics have been already subscribed."
}
```
If the URI in the topic name specifies a resource that is not in the configuration and state database, the following error is returned:
```
{"type":"error","message":"Object not found."}
```

Example of a message returned by a successful subscription attempt:

{
  "type": "success",
  "subscriber_name": "4bcf8uka90ki",
  "subscription_name": "ns83n58dky",
  "data": [
    {
      "topicname": "/rest/v1/system/bridge/vlans/DEFAULT_VLAN_1?attributes=admin,oper_state_reason",
      "resources": [
        {
          "operation": "",
          "uri": "/rest/v1/system/bridge/vlans/DEFAULT_VLAN_1",
          "values": {
            "admin": "up",
            "oper_state_reason": "no_member_port"
          }
        }
      ]
    },
    {
      "topicname": "/rest/v1/system/vrfs",
      "resources": [
        {
          "operation": "",
          "uri": "/rest/v1/system/vrfs/default",
          "values": {}
        },
        {
          "operation": "",
          "uri": "/rest/v1/system/vrfs/mgmt",
          "values": {}
        }
      ]
    }
  ]
}