建立MQTT连接
## 建立 MQTT 连接
函数原型|wait_at_mqttconn(uint8_t* ip,uint16_t port,uint8_t* clientid,uint16_tkeeplive,uint8_t cleansession,uint8_t* username,uint8_t* password)
|-|-|
功能 |回调AT+MQTTCONN=<host>,<port>,<clientid>,<keepalive>,<cleansession>, [username],[password] 建立 MQTT 连接
形参说明 ||ip：服务器地址
||port:端口号
||clientid:设备 ID
||keepalive:保活时间
||cleansession：是否清除 session，数字类型，0-不清除 1-清除，默认为 0
||username:用户名
||password:密码
返回值 |NA
```language
wait_at_mqttconn(“183.230.40.39”,6002,"534808251",120,0,"259084","subscribe");
```