Sidepit NNG communication protocols

Getting Started

1. Navigate to education/nng

cd education/nng

2. Create a Virtual Environment

python -m venv .env

3. Activate the Virtual Environment

Windows:

.env\Scripts\activate

Mac/Linux:

source .env/bin/activate

4. Install pynng

pip install pynng

5. Install nngcat

Mac

brew install nng

Linux

sudo apt-get install nng

6. Navigate to the Desired Communication Folder

To navigate into a specific communication protocol folder, use one of the following commands:

cd pubsub

cd pushpull

cd reqrep

7. Test the Protocol

Open two terminal windows and run the appropriate file in each one:

• Pub/Sub: Run publisher.py first, then subscriber.py.
• Req/Rep: Run reply.py first, then request.py.
• Push/Pull: Run push.py first, then pull.py.

What is Pub/Sub?

Pub/Sub (Publish/Subscribe) is a messaging pattern where a publisher sends messages to specific topics, and subscribers who have subscribed to those topics receive the messages.

Example Code in Python

# pubsub/publisher.py
import pynng
import time

with pynng.Pub0() as pub:
    pub.listen("tcp://127.0.0.1:5001")
    while True:
        pub.send(b"Hello, from Sidepit!")
        time.sleep(1)

# pubsub/subscriber.py
import pynng

with pynng.Sub0() as sub:
    sub.dial("tcp://127.0.0.1:5001")
    sub.subscribe(b"")
    while True:
        message = sub.recv()
        print(f"Received: {message.decode()}")

Example Using The Command Line

# Open the first terminal and run this command FIRST:
nngcat --pub --listen tcp://127.0.0.1:5001 --data "cuckoo" --interval 1

# Open the second terminal and run this command SECOND:
nngcat --sub --dial tcp://127.0.0.1:5001 --quoted

What is Req/Rep?

Req/Rep (Request/Reply) is a messaging pattern where a client sends a request to a server, and the server processes the request and sends back a reply.

Example Code in Python

# reqrep/request.py
import pynng
import time

with pynng.Req0() as req:
    req.dial("tcp://127.0.0.1:5001")
    while True:
        req.send(b"Send me a message...")
        reply = req.recv()
        print(reply.decode())
        time.sleep(1)

# reqrep/reply.py
import pynng

with pynng.Rep0() as rep:
    rep.listen("tcp://127.0.0.1:5001")
    while True:
        received_message = rep.recv()
        print(received_message.decode())
        rep.send(b"Hello, from Sidepit!")

Example Using The Command Line

# Open the first terminal and run this command FIRST:
nngcat --rep --listen tcp://127.0.0.1:5001 --data "42" --quoted     

# Open the second terminal and run this command SECOND:
nngcat --req --dial tcp://127.0.0.1:5001 --data "what is the answer?" --quoted                                               

What is Push/Pull?

Push/Pull is a messaging pattern often used for task distribution where a producer (or pusher) sends messages (tasks or jobs) to workers (or pullers). The workers pull these messages and process them.

Example Code in Python

# pushpull/push.py
import pynng

with pynng.Push0() as push:
    push.listen("tcp://127.0.0.1:5001")
    while True:
        push.send(b"Hello from push")

# pushpull/pull.py
import pynng
import time

with pynng.Pull0() as pull:
    pull.dial("tcp://127.0.0.1:5001")
    while True:
        received_message = pull.recv()
        print(received_message.decode())
        time.sleep(1)

Example Using The Command Line

# Open the first terminal and run this command FIRST:
nngcat --push --listen tcp://127.0.0.1:5001 --data "Here is a job for you..."                          

# Open the second terminal and run this command SECOND:
nngcat --pull --dial tcp://127.0.0.1:5001 --quoted                        

Common Functions

• listen(): Opens a socket to listen for incoming connections or messages.
• dial(): Initiates a connection to a remote socket by dialing to it.
• subscribe(): Subscribes to messages from a specific set of topics. Used by subscribers in a Pub/Sub pattern only.
• send(): Sends a message through the socket to the connected peer.
• recv(): Receives a message from the connected peer.
• decode(): Converts the received message from a binary format into a string or other usable format.

For a complete list of methods, please visit the pynng documentation and the nngcat command line methods.