Zmq

ZeroMQ

looks like its similar to mqtt but faster and more flexiable written in c/c++, and supports bindings in python (most docs are in c++) does not require a server

Frames

frames are (message parts) blocks of data with specific length. has garente of being recieved at the other end
to send large files spliting up into parts.

Sending strings

sent with out a trialing NULL 'asdfasdf\0' is 'asdfa\0'
- have specified length

Normal Sockets vs zmq sockets

normal: client and server make connection
zmq: each connection to socket creates its own que, allowing for 1-many, many-1, many-many
- ROUTER: is the acception, only create que if peer has acknowleged the connection, AKA confirm before setup
Ha funny: form a karmic circle of socket life ZeroMQ | Socket API

Python Client example Hello World client in Python - ØMQ - The Guide

import zmq

context = zmq.Context()

#  Socket to talk to server
print("Connecting to hello world server…")
socket = context.socket(zmq.REQ)
socket.connect("tcp://localhost:5555")

#  Do 10 requests, waiting each time for a response
for request in range(10):
    print("Sending request %s …" % request)
    socket.send(b"Hello")

    #  Get the reply.
    message = socket.recv()
    print("Received reply %s [ %s ]" % (request, message))

Python Server example Hello World server in Python - ØMQ - The Guide

t time
import zmq

context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://*:5555")

while True:
    #  Wait for next request from client
    message = socket.recv()
    print("Received request: %s" % message)

    #  Do some 'work'
    time.sleep(1)

    #  Send reply back to client
    socket.send(b"World")

Because zmq doesnt require trailing null in string being sent
- can cause weird results. rule of thumb copy string a terminate with \0 every time

ZeroMQ book Notes

One-way data distrobution

weather server zmq.PUB

import zmq
from random import randrange

context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://*:5556")

while True:
    zipcode = randrange(1, 100000)
    temperature = randrange(-80, 135)
    relhumidity = randrange(10, 60)

    socket.send_string("%i %i %i" % (zipcode, temperature, relhumidity))

weather client zmq.SUB

import sys
import zmq

#  Socket to talk to server
context = zmq.Context()
socket = context.socket(zmq.SUB)

print("Collecting updates from weather server…")
socket.connect("tcp://localhost:5556")

# Subscribe to zipcode, default is NYC, 10001
zip_filter = sys.argv[1] if len(sys.argv) > 1 else "10001"

# Python 2 - ascii bytes to unicode str
if isinstance(zip_filter, bytes):
    zip_filter = zip_filter.decode('ascii')
socket.setsockopt_string(zmq.SUBSCRIBE, zip_filter)

# Process 5 updates
total_temp = 0
for update_nbr in range(5):
    string = socket.recv_string()
    zipcode, temperature, relhumidity = string.split()
    total_temp += int(temperature)

print("Average temperature for zipcode '%s' was %dF" % (
      zip_filter, total_temp / (update_nbr+1))
)