订阅并使用python阅读mqtt mosquitto上的几个主题paho

Question

我设法发布了几个主题并阅读其中的一个。我需要做的是听取并阅读所有已发布的主题并获取消息。这是我的代码使用方法：

1. 发布消息3个主题：

   #!/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. 1个主题订阅和阅读邮件

   #!/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

您可以拨打client.subscribe()功能多次订阅多个主题。

此外，您应该将呼叫移动到订阅on_connect回调以删除第一个循环的需要。

#!/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：

您也可以订阅多个主题一次性使用的语法如下

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