pub.py

from time import sleep

import zmq

context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://*:9001")

while True:
    socket.send_json(('vidar', {'foo': 'bar'}))
    sleep(1)

sub.py

import zmq

context = zmq.Context()

socket = context.socket(zmq.SUB)
socket.connect('tcp://localhost:9001')
socket.subscribe = bytes()                  # Works.
#socket.subscribe = bytes('vidar', 'utf8')  # Doesn't work :(

while True:
    (topic, message) = socket.recv_json()
    print('got {} on topic {}'.format(message, topic))