Python-socketio: How to emit message from server to client?

Question

On the server, since eventlet.wsgi.server(eventlet.listen(('', 5000)), app) is blocking, the next line sio.emit('message', "hello") does not run. How do I send message from server to client? Will I have to create another thread?

My server code:

import socketio
import engineio
import eventlet

sio = socketio.Server()
app = socketio.WSGIApp(sio, static_files={
    '/': {'content_type': 'text/html', 'filename': 'index.html'}
})

@sio.on('connect')
def connect(sid, environ):
    print('connect ', sid)

@sio.on('message')
def message(sid, data):
    print('message ', data)

@sio.on('disconnect')
def disconnect(sid):
    print('disconnect ', sid)

if __name__ == '__main__':
    eventlet.wsgi.server(eventlet.listen(('', 5000)), app)
    sio.emit('message', "hello")

My client code:

import socketio

sio = socketio.Client()

@sio.on('connect')
def on_connect():
    print('connection established')

@sio.on('message')
def on_message(data):
    print('message received with ', data)
    sio.emit('my response', {'response': 'my response'})

@sio.on('disconnect')
def on_disconnect():
    print('disconnected from server')

sio.connect('http://localhost:5000')
sio.emit('message',"this is my first message")

Answer 1

You have two options:

1. add your emit to the connect handler, so that it runs every time a new client connects to your server.

2. start a background task before you launch the server and do it from there.