Two subscribers, one with while loop, another cannot receive new ros message

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Hello, I am trying to make a program that starts reading camera frames with opencv and ros. Currently, I begin reading camera frames from raspberry pi camera when "start" signal is subscribed. "start" signal and opencv frame are published to another topic.

At some time, I send "end" signal to the subscriber. However, the subscriber cannot read new signal. When "start" signal came at the beginning, the callback function runs get_frame function and this function goes through while loop. So, new signals are not received at all.

class GetFrame:
def __init__(self, node_name):
    self.operate = rospy.Subscriber('operate', operate, self.callback)
    self.pub_frame = rospy.Publisher('img_camera', sendframe, queue_size=3)
    self.node_name = node_name
    self.net = None
    self.detect = None
    self.cap = None
    self.args = arg_parse()
    self.frame_data = sendframe()
    self.bridge = CvBridge()

def callback(self, data):
    if data.command == "init":
        self.initialize()
    elif data.command == "start":
        self.get_frame(data)
    elif data.command == "end":
        self.get_frame(data)

def initialize(self):
    self.net = cv2.dnn.readNetFromDarknet(self.args.config, self.args.weight)
    self.net.setPreferableBackend(cv2.dnn.DNN_BACKEND_OPENCV)
    self.net.setPreferableTarget(cv2.dnn.DNN_TARGET_CPU)

    # load DetectBoxes class
    self.detect = DetectBoxes(self.args.labels,
                              confidence_threshold=self.args.confidence,
                              nms_threshold=self.args.nmsThreshold)

    try:
        self.cap = cv2.VideoCapture(0)
    except IOError:
        sys.exit(1)

@staticmethod
def get_outputs_names(net):
    # names of network layers e.g. conv_0, bn_0, relu_0....
    layer_names = net.getLayerNames()
    return [layer_names[i[0] - 1] for i in net.getUnconnectedOutLayers()]

def get_frame(self, operate):
    # if start signal came before init signal
    # initialize net & camera
    if self.cap is None or not self.cap.isOpened():
        self.initialize()

    while self.cap.isOpened():
        has_frame, frame = self.cap.read()

        # if end of frame, program is terminated
        if not has_frame:
            break

        # Create a 4D blob from a frame.
        blob = cv2.dnn.blobFromImage(frame, 1 / 255, (self.args.resol, self.args.resol),
                                     (0, 0, 0), True, crop=False)

        # Set the input to the network
        self.net.setInput(blob)

        # Runs the forward pass
        network_output = self.net.forward(self.get_outputs_names(self.net))

        # Extract the bounding box and draw rectangles
        self.frame_data.percent, self.frame_data.coords = self.detect.detect_bounding_boxes(frame, network_output)

        print("FPS {:5.2f}".format(1000/elapsed))

        # publish frames + detected objects
        self.frame_data.operate = operate.command
        try:
            self.frame_data.frame = self.bridge.cv2_to_imgmsg(frame, encoding="passthrough")
            self.pub_frame.publish(self.frame_data)
        except CvBridgeError as e:
            print(e)

    self.log.publish(log_generator(self.node_name, "Camera closed"))
    # releases video and removes all windows generated by the program
    # cap.release()


 if __name__ == '__main__':
     rospy.init_node('get_frame', anonymous=True)
     g_frame = GetFrame('get_frame')
     try:
         rospy.spin()
     except KeyboardInterrupt:
         print("Shut down - keyboard interruption")

Should I stop while loop? How can I subscribe new message while not ending while loop?

Thank you