上报keepalive信息

MindEdge OM会按照heartbeat参数设置的时间间隔（默认时间间隔为15秒），定时上报一次keepalive信息，确保设备在线。

消息实例

{
    "header" : {
        "msg_id" : "e33f7bff-a2fa-4f26-821b-37bdfa848b9d",
        "parent_msg_id": "",
        "timestamp" : 1642645840936,
        "sync": false
    },
    "route" : {
        "source" : "websocket",
        "group" : "resource",
        "operation" : "keepalive",
        "resource" : "node"
    },
    "content" : "ping"
}