1. Install paho-mqtt client pip install paho-mqtt

2. Install mosquitto broker https://mosquitto.org/download/ for windows and sudo apt-get install mosquitto in linux

3. Run: python3 alice.py <client_id> <topic_name> <secure(1)/not_secure(0)>

4. Run: python3 bob.py <client_id> <topic_name> <secure(1)/not_secure(0)>

5. Run: python3 eve.py <client_id> <topic_name> <secure(1)/not_secure(0)>

Keep all the client ids different and make each client subscrie to same topic. In a secure (1) channel eve would not be able to listen in on the coversation between Alice and Bob.