Is there a way in Flask-SocketIO to have a blocking/synchronous emit('event', callback) function that waits for the callback passed to it before returning?
Or -- is there a way to directly invoke the callback in an @socketio.on('event') handler instead of the plain return from that handler?
This is my situation specifically:
+-----------------+ +----------------------+ +----------------------+
| Browser | emit('serverGiveData', | Flask | emit('workerGiveData', | Worker |
| (webapp, JS) | browser_callback) | web server | server_callback) | (Python program) |
| | +------------------------> | | +--------------------> | |
| | | | | |
| socket.io 1.7.3 | data | Flask-SocketIO 2.8.2 | data |socketiIO-client 0.7.2|
| | <------------------------+ | | <--------------------+ | |
| | | | | |
+-----------------+ +----------------------+ +----------------------+
So the Browser wants data from the Worker and the Flask web server is just a proxy in between.
I would like the browser_callback() to be invoked after the Server receives the data from the Worker.
(I.e. I would like to call the browser_callback() from the server_callback()).
However, I cannot invoke the browser_callback() from server_callback() manually in Flask-SocketIO -- it is "automatically" invoked when I return from 'serverGiveData' handler function on the Server. That is why I would like to have a blocking/synchronous emit('workerGiveData') so that the handler on the Server doesn't return before the Worker delivers the data.
Here's the code
Browser
socketio.emit('serverGiveData', args, function (data) {
console.log('Received data');
});
Server
@socketio.on('serverGiveData')
def handler(msg):
socketio.emit('workerGiveData', msg, callback=server_callback)
return # When server_callback() gets called back
def server_callback(data):
print('Received data from Worker')
# Here I want to invoke client_callback(), i.e.
# I don't want handler() to return before this server_callback() is invoked
Worker
def handler(args, callback);
callback(data)
socketIO.on('workerGiveData', handler)
(I am aware I could emit('heyBrowserHeresData') from the server_callback() when the Worker delivers the data and listen on that event in the browser with browser_callback() code as the handler.
I would like to avoid that jumble.)
