Flask Socket-IO and React socket.io-client, client doesn't receive messages from 'emit

Question

I want to send message to client (React JS) from another thread (because there I start basic consuming messages from pika and it blocks Flask app). That's my simple code at client side:

const socket = io.connect('ws://127.0.0.1:5000',{transports: ['websocket'], secure: true, port: '5000'});

useEffect(()=> {
    socket.emit("echo", "echo");
}, [])

socket.on('echoresponse', (data) => {
    console.log(data);
});


socket.on('update_page', (data) => {
    console.log(data);
});

When server receives echo, it answers back and everything work ok. But when I try to emit from send_result_in_thread(), client receives nothing. My server side (missing some rabbitmq pika code)

    clients = []
    app = Flask(__name__)
    socketIo = SocketIO(app, async_mode='eventlet', cors_allowed_origins="*")
    eventlet.monkey_patch()
    app.debug = True
    app.host = 'localhost'
    app.debug = True
    app.host = 'localhost'
    
 def send_result_in_thread(cli, message):
    for client in cli:
            socketIo.emit('update_page', message, room=client)
            print('sending message "{}" to client {}'.format(message.decode("utf-8"), client))
    
@socketIo.on("echo")
def echo( message):
     emit('echoresponse', "I'm alive")
    
@socketIo.on('connect')
  def handle_connect():
      print('Client connected')
      clients.append(request.sid)
    
    
@socketIo.on('disconnect')
def handle_disconnect():
     print('Client disconnected')
     clients.remove(request.sid)
    
if __name__ == '__main__':
    consumer = consumer.Consumer()
    t = threading.Thread(target=consumer.run, name="run", args=(clients, ))
    t.daemon = True
    t.start()
    socketIo.run(app, host='0.0.0.0', port='5000',
                     debug=True)

Another thread:

class Consumer():
    def __init__(self):
        self.clients = []
        #and some more code for rabbitmq

    def got_result(self, ch, method, properties, body):
        print("CLIENTS from thread:" + str(self.clients))
        socketIo.start_background_task(send_result_in_thread, self.clients, body)

    def run(self, clients):
        self.clients = clients
        self.channel.basic_consume(self.queue_name, self.got_result)
        self.channel.start_consuming()

I found similar problem here and used as a reference https://stackoverrun.com/ru/q/12599436 But it doesn't help solving the problem. Client_id is passed to thread successfully, the send_result_in_thread is called but client doesn't receive message. I have no idea why. Thanks in advance.

Set a breakpoint to see if any connection is made and set your echo to run on the connected event callback. — John
– John, Commented Nov 24, 2020 at 22:49
Thanks, I solved it! the problem was different socketIo objects in threads @John — bumblebee
– bumblebee, Commented Nov 25, 2020 at 9:46

bumblebee · Accepted Answer · 2020-11-25 09:49:47Z

2

Finally I've found the problem. Every thread had his own socketIo variable, so message was not send to client. My solution: In main:

t = threading.Thread(target=consumer.run, name="run", args=(clients, socketIo))

In run:

self.socketIo = socketIo

And in got_result:

performer.socketIo.start_background_task(performer.send_result_in_thread, self.clients, self.socketIo, body.decode("utf-8"))

answered Nov 25, 2020 at 9:49

bumblebee

1413 silver badges12 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Flask Socket-IO and React socket.io-client, client doesn't receive messages from 'emit

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related