test.py

# SERVER
import paho.mqtt.publish as publish
 
MQTT_SERVER = "localhost"
MQTT_PATH = "test_channel"
 
publish.single(MQTT_PATH, "Hello World!", hostname=MQTT_SERVER)

##########

#CLIENT
import paho.mqtt.client as mqtt
 
MQTT_SERVER = "192.168.4.1"
MQTT_PATH_COMMAND = "command_channel"
MQTT_PATH_REPLY = "reply_channel"
 
# 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(MQTT_PATH_COMMAND)
    client.subscribe(MQTT_PATH_REPLY)
 
# 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.publish(MQTT_PATH_REPLY, "TEST TEST TEST", qos=0, retain=False)
    # more callbacks, etc
 
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
 
client.connect(MQTT_SERVER, 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()