Appearance
AT+CIFSR
ATE0
ATE1
https://docs.espressif.com/projects/esp-at/zh_CN/latest/esp32/AT_Command_Examples/at_msg_resp_fmt_ctrl_examples.html
\r\nOK\r\n
连接tcp
AT+CIPSTART="TCP","a1saawdoLLP.iot-as-mqtt.cn-shanghai.aliyuncs.com",1883