使用micropython怎样实现使用mqtt接入物联网云平台同时实现订阅和发送，给出示例程序

你好，以下是示例程序：

import network
from umqtt.simple import MQTTClient

# 设置WiFi连接信息
ssid = "your_wifi_ssid"
password = "your_wifi_password"

# 设置MQTT连接信息
mqtt_server = "your_mqtt_server"
mqtt_port = 1883
mqtt_user = "your_mqtt_user"
mqtt_password = "your_mqtt_password"
mqtt_topic = "your_mqtt_topic"

# 连接WiFi
sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.connect(ssid, password)
while not sta_if.isconnected():
    pass

# 连接MQTT
client = MQTTClient("esp8266", mqtt_server, mqtt_port, mqtt_user, mqtt_password)
client.connect()

# 订阅MQTT主题
def sub_cb(topic, msg):
    print((topic, msg))

client.set_callback(sub_cb)
client.subscribe(mqtt_topic)

# 发送MQTT消息
client.publish(mqtt_topic, "Hello from micropython!")

# 循环等待MQTT消息
while True:
    client.check_msg()

以上程序使用micropython实现了连接WiFi和MQTT，并实现了订阅和发送MQTT消息。请根据实际情况修改程序中的WiFi和MQTT连接信息。