Sending/Receiving messages on the EventBus using ZMQ

Receiving messages

Components inside Openvisulizer use messages to communicate with each other. There is a lot of messages. Subscribing to all of them will impact the latency of Openvisualizer and it's also likely that you are only interested in a subset of all messages.

You can use the control plane socket to set up which kind of messages you want to receive:

#!/usr/bin/env python

import zmq 

context = zmq.Context()                                                                                                                           
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:50001")
# To subscribe
socket.send_json({"sub": ["bonjour"]})
# To unsubscribe
# socket.send_json({"unsub": ["bonjour"]})
# you can even do both
# socket.send_json({"sub": ["Hello"], "unsub": ["bonjour"]})
message = socket.recv()
print(message) # You will get the subscriptions of the PUB socket {"subscriptions":["Hello"]}

Once this is set up, you can receive messages using a snippet of code similar to this :

#!/usr/bin/env python

import zmq 

context = zmq.Context()  
subscriber = context.socket(zmq.SUB)
subscriber.connect("tcp://localhost:50002")
subscriber.setsockopt(zmq.SUBSCRIBE, "")
while True:
	string = subscriber.recv_json()
	print(string)

Sending messages

There is a REP socket waiting to receive message and inject them directly in the message bus. You can send message to the event bus by using a ZMQ REQsocket like this:

 #!/usr/bin/env python
import zmq
import time
d = {'signal': "bonjour", "sender": u"poipoi", "data": "hello world!"}

context = zmq.Context()
publisher = context.socket(zmq.REQ)
publisher.connect("tcp://localhost:60000")
count = 0
while True:
    count += 1
    publisher.send_json(d)
    message = publisher.recv_json()
    print "message {0} ".format(count),message
    time.sleep(2)

Related Issue : SW-263 - Getting issue details... STATUS