mqtt python测试脚本

1. on_message回调函数
   回调函数无法返回message，只能在函数体里面进行操作，所以将message写入数据库，然后在数据库中去查询。

def on_message(client, userdata, msg):
    mss =  str((msg.payload).decode('utf-8'))    
    #print(msg.topic + " " + mss)
    insert_msg(msg.topic, mss)

2. sqlite数据库
   使用参数输入

c.execute("REPLACE INTO mqtt (TOPIC, MSG) VALUES ('%s', '%s')" %(topic, msg))

返回的数据是一个数组，数组每个元素是一条记录元组，所以要获取值需要这样处理：

c.execute("select msg from mqtt where topic = '%s'" %(topic))
    mss = c.fetchall()[0][0]

3. mqtt
   订阅的测试方法，需要先连接，然后启动loop，订阅topic，发送消息，停止loop

client = mqtt_connect(MQTT_SERVER_ADDR, MQTT_SERVER_PORT,PRODUCT_KEY, DEVICE_NAME,DEVICE_SECRET, TIMESTAMP)
        client.loop_start()
        mqtt_subscribe(client, self.TOPIC_REPORT)
        mqtt_publish(client, self.TOPIC_REPORT, MSG)
        time.sleep(4)
        client.loop_stop()