测试用例不稳定

[ErnestChen1]

使用默认的id，key，name，secret 等，正常连接wifi，功能显示不稳定，偶尔正常。依据常见错误解决及处理方法，这些参数正确的情况下，不会出错，并且如果能够正常连接，那么不会存在赋值错误的情况。因此，简单的说就是性能不稳定，希望能够查找

日志如下：
tc_mqtt_shadow_example
msh />tc_mqtt_shadow_example
TC MQTT Shadow Exmaple,TC_IOT_SDK_VER:2.9TRACE tc_iot_hmsh />al_udp_connect:270 tc_iot_hal_udp_connect entry
TRACE tc_iot_hal_udp_connect:300 The host IP 193.228.143.12, port is 123

DEBUG _get_timestamp_from_ntp:199 udp fd (4)
TRACE tc_iot_hal_udp_write:252 tc_iot_hal_udp_write entry, len=48 timeout=0ms
TRACE tc_iot_hal_udp_read:201 tc_iot_hal_udp_read entry, len=1500 timeout=10000ms
ERROR _get_timestamp_from_ntp:218 udp read error!
TRACE tc_iot_hal_udp_disconnect:341 network disconnected
TRACE tc_iot_hal_udp_destroy:351 network destroied
requesting username and password for mqtt.
92b0e676cdd608c4fb56386967613764|clientId=mqtt-1egtdjqza@rt_thread_dev1&deviceName=rt_thread_dev1&nonce=1190908873&productId=iot-1l60dtl0&timestamp=3735928559
TRACE tc_iot_mqtt_refresh_dynamic_sign:1246 usename[rt_thread_dev1] password[productId=iot-1l60dtl0&nonce=1190908873&timestamp=-559038737&signature=tWLNA+c+BCtmaiyQQsUf0m
request username and password for mqtt success.
INFO tc_iot_server_init:383 constructing mqtt shadow client.
TRACE tc_iot_mqtt_init:224 mqtt client buf_size=1024,readbuf_size=1024
TRACE tc_iot_hal_udp_connect:270 tc_iot_hal_udp_connect entry
TRACE tc_iot_hal_udp_connect:300 The host IP 193.228.143.12, port is 123

DEBUG _get_timestamp_from_ntp:199 udp fd (4)
TRACE tc_iot_hal_udp_write:252 tc_iot_hal_udp_write entry, len=48 timeout=0ms
TRACE tc_iot_hal_udp_read:201 tc_iot_hal_udp_read entry, len=1500 timeout=10000ms
ERROR _get_timestamp_from_ntp:218 udp read error!
TRACE tc_iot_hal_udp_disconnect:341 network disconnected
TRACE tc_iot_hal_udp_destroy:351 network destroied
TRACE tc_iot_hal_net_connect:179 tc_iot_hal_net_connect entry
TRACE tc_iot_hal_net_connect:196 host:(mqtt-1egtdjqza.ap-guangzhou.mqtt.tencentcloudmq.com) port:(1883)
TRACE tc_iot_hal_net_connect:236 connect host((NULL)) success, fd=4
TRACE _send_packet:151 entry length=177
TRACE tc_iot_hal_net_write:99 tc_iot_hal_net_write entry, len=177 timeout=29997ms
TRACE _send_packet:169 rc=0
TRACE tc_iot_hal_net_read:32 tc_iot_hal_net_read entry, len=1 timeout=29986ms
TRACE tc_iot_hal_net_read:32 tc_iot_hal_net_read entry, len=1 timeout=31309ms
TRACE tc_iot_hal_net_read:32 tc_iot_hal_net_read entry, len=2 timeout=31302ms
ERROR tc_iot_mqtt_client_connect:48 mqtt cllient connect mqtt-1egtdjqza.ap-guangzhou.mqtt.tencentcloudmq.com:1883 failed retcode -165
tc_iot_server_init failed, trouble shooting guide: https://git.io/vN9le#-165