<LinkID>,1,<"client_id">,<"username">,<"password">,0,0,""

AT+MQTTUSERCFG=0,1,"ESP32","espressif","1234567890",0,0,""


AT+MQTTCONN=0,"192.168.1.15",1883,0

AT+MQTTPUB=0,"/sys/post","hello",0,0
异常："busy p..."


数据接收：
AT+MQTTSUB=<LinkID>,<"topic">,<qos>
AT+MQTTSUB=0,"/sys/set",0


然后在中断消息分发器中去判断一下：
+MQTTSUBRECV:<LinkID>,<"topic">,<data_length>,data




数据发送：
AT+MQTTPUBRAW=<LinkID>,<"topic">,<length>,<qos>,<retain>
AT+MQTTPUBRAW=0,"/sys/post",52,0,0								//实际长度+1  因为结尾\0

OK																//接收到OK就开始发
{"hello":22,"222":88,"qq":{"num":"815","pwd":"77"}}				//发送内容