如何同时运行多个发布者 paho-mqtt？

Question

I am running a single script with several clients publishing to the same topic, 5 messages each, but they do it one after another. I would like to know if there is any way to execute several publishers but at the same time and not for a loop "for "as I programmed it.

It occurred to me to run various python scripts but it is not functional if I want to have for example 100 publishers. Anyone have an idea how I could do it? Thanks in advance

import ssl
import time 
import random
import sys  
import paho.mqtt.publish as publish
import paho.mqtt.client as mqtt
from datetime import datetime

broker_address = '127.0.0.1'
topic = "casa/hab1"
port=1883
delay=0.2
count=0
i=0
j=0
nclients=1
nmessages=5


for i in range(nclients):
  cname="Client"+str(i) 
  j=int(time.time()) #eliminar la parte decimal
  j=str(j)
  client_id=cname+str(j)+"_" #generar client_id
  client=mqtt.Client(client_id) 
  client.connect(broker_address)  
  print("")

  print(str(client_id))
  client.loop_start() 

  for count in range(nmessages):
     b=random.randrange(10, 99, 1)
     mensaje="Hello World:"+ str(b)+" -- "
     client.publish(topic,mensaje, 2, retain=False) 
     now=datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")
     print("timestamp "+str(count)+" = "+now)
     
     count+=1
     time.sleep(delay)

  i+=1

Answer 1

Normally to run many functions at the same time you would need to use threading or multiprocessing to run every function in separated thread / process .

But client.loop_start() already runs thread so you can first create many clients,

all_clients = []

for i in range(nclients):
    t = int(time.time())

    client_id= "Client_{}_{}_".format(i, t) 
    print('create:', client_id)
    
    client = mqtt.Client(client_id) 
    client.connect(broker_address)  
    client.loop_start() 

    all_clients.append([client_id, client])

and later use them in loop which sends messages

for count in range(nmessages):

    for client_id, client in all_clients: 
        b = random.randrange(10, 99, 1)
        mensaje = "Hello World: {} -- ".format(b)
        client.publish(topic, mensaje, 2, retain=False) 
        now = datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")
        print('client:', client_id, '| count:', count, "=", now)

    time.sleep(delay)

It will send almost in the same time (+- 0.01s) but running every client in separated thread / process to would be harder to run messages with so small delay.

---

import time 
import random
import paho.mqtt.publish as publish
import paho.mqtt.client as mqtt
from datetime import datetime

broker_address = '127.0.0.1'
#broker_address = '192.168.1.91'

topic = "casa/hab1"
delay = 0.2

nclients = 3
nmessages = 5

# --- first create all clients ----

all_clients = []
for i in range(nclients):
    t = int(time.time())

    client_id= "Client_{}_{}_".format(i, t) 
    print('create:', client_id)
    
    client = mqtt.Client(client_id) 
    client.connect(broker_address)  
    client.loop_start() 

    all_clients.append([client_id, client])

# ---

print()

# --- loop ---

for count in range(nmessages):

    for client_id, client in all_clients: 
        b = random.randrange(10, 99, 1)
        mensaje = "Hello World: {} -- ".format(b)
        client.publish(topic, mensaje, 2, retain=False) 
        now = datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")
        print('client:', client_id, '| count:', count, "=", now)

    time.sleep(delay)

Result:

create: Client_0_1600159539_
create: Client_1_1600159539_
create: Client_2_1600159539_

client: Client_0_1600159539_ | count: 0 = 2020-09-15 10:45:39.125615
client: Client_1_1600159539_ | count: 0 = 2020-09-15 10:45:39.126737
client: Client_2_1600159539_ | count: 0 = 2020-09-15 10:45:39.128049
client: Client_0_1600159539_ | count: 1 = 2020-09-15 10:45:39.329731
client: Client_1_1600159539_ | count: 1 = 2020-09-15 10:45:39.330702
client: Client_2_1600159539_ | count: 1 = 2020-09-15 10:45:39.332028
client: Client_0_1600159539_ | count: 2 = 2020-09-15 10:45:39.533360
client: Client_1_1600159539_ | count: 2 = 2020-09-15 10:45:39.534323
client: Client_2_1600159539_ | count: 2 = 2020-09-15 10:45:39.535380
client: Client_0_1600159539_ | count: 3 = 2020-09-15 10:45:39.737049
client: Client_1_1600159539_ | count: 3 = 2020-09-15 10:45:39.738118
client: Client_2_1600159539_ | count: 3 = 2020-09-15 10:45:39.739249
client: Client_0_1600159539_ | count: 4 = 2020-09-15 10:45:39.941419
client: Client_1_1600159539_ | count: 4 = 2020-09-15 10:45:39.943207
client: Client_2_1600159539_ | count: 4 = 2020-09-15 10:45:39.944785

---

EDIT:

The same using threading .

In this version you can use random delay in every client to make all traffic more random.

import time 
import random
import paho.mqtt.publish as publish
import paho.mqtt.client as mqtt
from datetime import datetime
import threading

broker_address = '127.0.0.1'
#broker_address = '192.168.1.91'

topic = "casa/hab1"
delay = 0.2

nclients = 3
nmessages = 5

# --- functions ---

def sending(client, client_id):

    for count in range(nmessages):

        b = random.randrange(10, 99, 1)
        mensaje = "Hello World: {} -- ".format(b)
        client.publish(topic, mensaje, 2, retain=False) 
        now = datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")
        print('client: {} | count: {} = {}'.format(client_id, count, now))
        #delay = random.randint(1, 5) / 10

        time.sleep(delay)

# --- first create all clients ----

all_clients = []
for i in range(nclients):
    t = int(time.time())

    client_id= "Client_{}_{}_".format(i, t) 
    print('create:', client_id)
    
    client = mqtt.Client(client_id) 
    client.connect(broker_address)  
    client.loop_start() 

    all_clients.append([client_id, client])

# ---

print()

# --- threads ---

all_threads = []

# start threads
for client_id, client in all_clients:
    t = threading.Thread(target=sending, args=(client, client_id))
    t.start()
    all_threads.append(t)
    
# ... other code ...

# at the end wait for end of threads
for t in all_threads:
    t.join()