Add call() support to Flask-SocketIO

[miguelgrinberg]

Discussed in #1828

^{Originally posted by alurmtr June 9, 2022}
I am using Flask-socketio and sending an emit to the client, and would like to wait for response before continuing in the code flow.

The case scenario is a background python code that needs feedback from user whether code should continue execution. An emit message is sent to the client, which in turns will send a js confirm pop-up window to the front end user. Based on the user selection, an acknowledgement is sent back to the python background process.

The callback option in the flask-socketio emit wouldn't work well. Something like the python-socketio call method would be great to just wait for the response. just wondering if there is such an option in flask-socketio.

Thanks
Al