为什么我不能在树莓派上使用 python-mosquitto？

Question

我正在使用带有 Debian Wheezy 映像的 Raspberry Pi。我已经安装了 Mosquitto（MQTT 协议的代理）、mosquitto 客户端和 python mosquitto，以便在我的 Python 脚本中使用 mosquitto，我运行了一个非常简单的示例来测试我的所有包是否都可以正常工作

import mosquitto
mqttc = mosquitto.Mosquitto("python_pub")
mqttc.will_set("/event/dropped", "Sorry, I seem to have died.")
mqttc.connect("127.0.0.1", 1883, 60, True)

mqttc.publish("hello/world", "Hello, World!")

由于某种原因，我收到以下错误。

Traceback (most recent call last):
File "test_1.py", line 1, in <module>
import mosquitto
File "/usr/lib/pymodules/python2.7/mosquitto.py", line 484, in <module>
_mosquitto_log_init = _libmosq.mosquitto_log_init
File "/usr/lib/python2.7/ctypes/__init__.py", line 378, in __getattr__
func = self.__getitem__(name)
File "/usr/lib/python2.7/ctypes/__init__.py", line 383, in __getitem__
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /usr/lib/libmosquitto.so.1: undefined symbol: mosquitto_log

有人可以解释为什么这不起作用以及可能的解决方案。

Answer 1

我实际上正在为我的大学开发一个项目，使用 mosquitto 作为 MQTT 的代理。我建议你使用 paho 作为 python 模块来使用 MQTT 发布和订阅。

官方页面：

https://pypi.python.org/pypi/paho-mqtt

这是一个非常简单的示例，它订阅了代理 $SYS 主题树并打印出结果消息（取自 https://pypi.python.org/pypi/paho-mqtt）：

import paho.mqtt.client as mqtt

# The callback for when the client receives a CONNACK response from the server.
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.
    client.subscribe("$SYS/#")

# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message

client.connect("iot.eclipse.org", 1883, 60)

# Blocking call that processes network traffic, dispatches callbacks and
# handles reconnecting.
# Other loop*() functions are available that give a threaded interface and a
# manual interface.
client.loop_forever()

Answer 2

Mosquitto Python 模块已捐赠给 Eclipse Paho 项目。它可以使用“pip install paho-mqtt”安装，在https://pypi.python.org/pypi/paho-mqtt有可用的文档

Mosquitto Python 模块的现有用户应该会发现将他们的代码移植到 Paho 版本非常容易。

http://mosquitto.org/documentation/python/

来自https://eclipse.org/paho/clients/python/的官方例子：

import paho.mqtt.client as mqtt

# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, 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.
    client.subscribe("$SYS/#")

# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message

client.connect("iot.eclipse.org", 1883, 60)

# Blocking call that processes network traffic, dispatches callbacks and
# handles reconnecting.
# Other loop*() functions are available that give a threaded interface and a
# manual interface.
client.loop_forever()

试一试！