CODEWITHSUNDEEP
pythonnumpyopencvnetwork-programmingzeromq
Mr. Randy Tom
Mr. Randy Tom

Reputation: 321

How to fetch opencv frames with ZeroMQ?

I'm using the following code to fetch the frames from the client :

def fetch_frame(self):

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

    while True:
        frame = footage_socket.recv_string()

        frame = frame.encode()

        img = base64.b64decode(frame)

        npimg = np.fromstring(img, dtype=np.uint8)
        source = cv2.imdecode(npimg, 1)

Unfortunately, it is throwing the following error :

zmq.error.ZMQError: Operation cannot be accomplished in current state

What is the proper way to retrieve image using zmq?

UPDATE:

Following is the traceback :

 File "/home/receive/main.py", line 77, in <module>
    main()
  File "/home/receive/main.py", line 73, in main
    ci.fetch_frame()
  File "/home/receive/main.py", line 59, in fetch_frame
    frame = footage_socket.recv_string()
  File "/home/.local/lib/python3.8/site-packages/zmq/sugar/socket.py", line 608, in recv_string
    msg = self.recv(flags=flags)
  File "zmq/backend/cython/socket.pyx", line 791, in zmq.backend.cython.socket.Socket.recv
  File "zmq/backend/cython/socket.pyx", line 827, in zmq.backend.cython.socket.Socket.recv
  File "zmq/backend/cython/socket.pyx", line 191, in zmq.backend.cython.socket._recv_copy
  File "zmq/backend/cython/socket.pyx", line 186, in zmq.backend.cython.socket._recv_copy
  File "zmq/backend/cython/checkrc.pxd", line 26, in zmq.backend.cython.checkrc._check_rc
zmq.error.ZMQError: Operation cannot be accomplished in current state

Upvotes: 0

Views: 342

Answers (1)

user3666197
user3666197

Reputation: 1

Q : "ZMQError: Operation cannot be accomplished in current state"

The core reason is, that your code violated ZeroMQ REQ/REP documented properties.

Asking REP-instance to .send()-ed message before a REQ-instance has already "asked" its counterparty first, the API has to throw such error.

Similarly, if trying to .recv() a message on the REQ-side, before it has first "asked" by a .send() the REP-side ( to reply ), the API has to throw such error.

SOLUTION ?

In a case no other interaction is needed, a PUSH/PULL Scalable Formal Communication Pattern Archetype, where PUSH-side will .send() & the PULL-side will .recv(), is IMHO the best way ahead.

You might like to read more tips and links about this in this.

Upvotes: 1

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