在 sysmd 单元上运行 python 脚本：time.sleep 超过 60 秒不起作用

Question

我在我的 RaspberryPi 上运行一个 systemd unit python 脚本，以便在 Pi 通电时自动发送温度数据。当 time.sleep 为 60 秒时，一切正常。但是当 time.sleep 更长（120 秒或更多）时，它只会在脚本启动时发送一个值，之后我不会再获得任何值。有人可以帮忙吗？

import paho.mqtt.client as mqtt
import Adafruit_DHT
import time
import ssl

# Set up DHT22 sensor
dht_sensor = Adafruit_DHT.DHT22
dht_pin = 4  # GPIO pin number the sensor is connected to

username = 'master:mqttuser'
secret = 'ifYmQ8HeUhperGnqXTLEtDSc'
host = '192.168.0.65'
port = 8883
clientID = 'raspi_ka'
assetID = '3nRdM1k6UfjggE0Ga'


def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))

    # Subscribing in on_connect() means that if we lose the connection and
    # reconnect then subscriptions will be renewed.
    mqtt_client.subscribe("$SYS/#")


def on_publish(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))


mqtt_client = mqtt.Client(clientID)
mqtt_client.username_pw_set(username, password=secret)
context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
mqtt_client.tls_set_context(context)
mqtt_client.on_connect = on_connect
mqtt_client.on_publish = on_publish
mqtt_client.connect(host, port=port)

# Continuously read and send temperature values
while True:
    humidity, temperature = Adafruit_DHT.read_retry(dht_sensor, dht_pin)
    if humidity is not None and temperature is not None:
        mqtt_client.publish(f"master/{clientID}/writeattributevalue/temperature/{assetID}", temperature)
        mqtt_client.publish(f"master/{clientID}/writeattributevalue/humidity/{assetID}", humidity)
    else:
        print("Failed to read temperature sensor data")
    time.sleep(120)

# Disconnect MQTT client
mqtt_client.disconnect()

Answer 1

您因超时而断开连接。您必须设置

keepalive

参数才能连接。

mqtt_client.connect(host, port=port, keepalive=120)

请注意，

time.sleep()

不准确。它可能会延长任意数量。您可能想改用 MQTT 客户端的

loop

功能。

while True:
    ...
    mqtt_client.loop(timeout=120)