{
  "description":"listen on the message from the broker",
  "spec": {
    "id": "__HOPE__/demo/mockup/hub_a/mqtt/subscribe",
    "in": {
      "ports": [{
        "name": "on",
        "type": "boolean"
        }]
    },
    "out": {
      "ports": [{
        "name": "message",
        "type": "string"
      }]
    },
    "config": [
      {
        "name": "server",
        "required": true
      }, {
        "name": "topic",
        "type": "string",
        "required": true
      }
    ]
  }
}