Running flask-socket-io using Python 3.5 I ran into the following issue when trying to send a message with an event name containing a dash.

From .js client:

socket.on('connect', function() {
    socket.emit('connect-event', {data :  'Client connected'});
});

Error in Python 3.5
ValueError: invalid literal for int() with base 10:

Points to:
packet.py line 84