使用 python paho 订阅并阅读 mqtt mosquitto 的几个主题

Question

我设法发表了几个主题并阅读了其中一个。我需要做的是聆听和阅读所有已发布的主题并获取消息。这是我使用的代码：

1. 向 3 个主题发布消息：

   #!/usr/bin/env python3
   
   
   import paho.mqtt.client as mqtt
   
   client = mqtt.Client()
   client.connect("localhost",1883,60)
   client.publish("topic/1", "400 | 350 | 320 | 410");
   client.publish("topic/2", "200 | 350 | 420 | 110");
   client.publish("topic/3", "200 | 350 | 420 | 110");
   
   client.disconnect();
   

2. 订阅和阅读 1 个主题的消息

   #!/usr/bin/env python3
   
   import paho.mqtt.client as mqttClient
   import time
   
   def on_connect(client, userdata, flags, rc):
   
   if rc == 0:
   
       print("Connected to broker")
   
       global Connected                #Use global variable
       Connected = True                #Signal connection 
   
   else:
   
       print("Connection failed")
   
   def on_message(client, userdata, message):
   print "Message received : "  + message.payload
   
   Connected = False   
   
   broker_address= "localhost"          
   port = 1883                          
   
   client = mqttClient.Client("Python")          
   client.on_connect= on_connect    
   client.on_message= on_message        
   client.connect(broker_address, port=port)     
   client.loop_start()        
   
   while Connected != True:   
       time.sleep(0.1)
   
   client.subscribe("topic/2")
   try:
   while True:
       time.sleep(1)
   
   except KeyboardInterrupt:
   print "exiting"
   client.disconnect()
   client.loop_stop()
   

Answer 1

您可以多次调用client.subscribe()函数订阅多个主题。

您还应该将调用移动到订阅on_connect 回调，以消除对第一个循环的需要。

#!/usr/bin/env python3

import paho.mqtt.client as mqttClient
import time

def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print("Connected to broker")
        client.subscribe("topic/1")
        client.subscribe("topic/2")
        client.subscribe("topic/3")
        client.subscribe("topic/4")

    else:
        print("Connection failed")

def on_message(client, userdata, message):
    print("Message received : "  + str(message.payload) + " on " + message.topic)


broker_address= "localhost"          
port = 1883                          

client = mqttClient.Client("Python")          
client.on_connect= on_connect    
client.on_message= on_message        
client.connect(broker_address, port=port)     
client.loop_start()


try:
    while True:
        time.sleep(1)

except KeyboardInterrupt:
    print("exiting")
    client.disconnect()
    client.loop_stop()

编辑：

您还可以使用以下语法一次性订阅多个主题

client.subscribe([("topic/1", 0), ("topic/2", 0), ("topic/3", 0),("topic/4", 0)])