查询商家是否在线
<pre><code>{"cmd":"is_online","link":"Tkzljq"}</code></pre>
<h1></h1>
<pre><code>{
"cmd": 8,
"msg": "success",
"from_uid": null,
"from_user_type": null,
"to_uid": null,
"to_user_type": null,
"data": {
"online": 0
},
"extra": "",
"time": 1555924860,
"need_notice": 1,
"message_id": null,
"from_name": null
}</code></pre>