Flask-Socktio

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Start

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from flask_socketio import SocketIO

socketio = SocketIO(app)

Receiving Messages

The event name is determined. 'message', 'json', 'xxx event', you can determine these name as socket name. Particularly 'connect', 'disconnecte' can be called when connecting or disconnecting.

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@socketio.on('xxx event', namespace='/test')
def handler(json):
  print('receive json: ', str(json))
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<script>
	var socket = io.connect('http://0.0.0.0:5001')
  socket.on('connect', function() {
    socket.emit('xxx event', {'data': 'connected.'})
  })
</script>

Sending Messages

emit() used for named events , send() used for unamed events.

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@socketio.on('xxx event', namespace='/chatroom')
def xxx_event():
  emit('xxx event', {'data': 'xxx'}, namespace='/chatroom')

Important

You can emit message in a router with socketio.emit('xxx event', resp, namespace='/chatroom').

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@app.rout('/send')
def send():
	socketio.emit('xxx event', resp, namespace='/chatroom')

You can’t use emit() without context of socketio, you should use socketio.emit().

Broadcasting

If broadcasting is enabled, all the clients connected to the namespace will receive the message.

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@socketio.on('xxx event', namespace='/chatroom')
def xxx_event():
  emit('xxx event', {'data': 'xxx'}, namespace='/chatroom', broadcast=True)

Rooms

Users can receive messages from the room they are in.

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@socketio.on('join')
def on_join(data):
    username = data['username']
    room = data['room']
    join_room(room)
    send(username + ' has entered the room.', to=room)

@socketio.on('leave')
def on_leave(data):
    username = data['username']
    room = data['room']
    leave_room(room)
    send(username + ' has left the room.', to=room)

Use to argument set which room the message should be sent to.

Class-Based Events

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from flask_socketio import Namespace, emit

class MyCustomNamespace(Namespace):
    def on_connect(self):
        pass

    def on_disconnect(self):
        pass

    def on_my_event(self, data):
        emit('my_response', data)

socketio.on_namespace(MyCustomNamespace('/test'))  # Assign namespace

All the event is defined by the methods with on_ prefix.

Reference

https://flask-socketio.readthedocs.io