From a web application, this is making a request to the backend application (Python with Flask and flask-socketio). From this route on the backend, an emit should be done to a socketio client standalone application. This works fine, but when the client app sends back a message directly after, I want to retrieve this message and send it back in my route to the web application. The message I get back from the client via a callback will be asynchronous, so how in the simplest manner could this be achieved? Each time I fetch the message from the client, the route has already sent back a reply to the web app without the message.
I fully understand that this flow is usually not normal, but can this be achieved without saving this message into a database, but store it somewhere on the backend and send it back to the web app?
You can use an Event object from the Python standard library.
from threading import Event
my_event = Event()
In your Flask route:
my_event.wait() # block until the event is signaled
return socketio_response
In your Socket.IO callback function:
socketio_response = data
my_event.set() # alert the route that a result is now available