flutter socketio client always connect failed

[hakanaku1234]

hello, I was trying to use flutter socketio client package to connect with flask-socketio, but i can't.

it always show this error message:
The client is using an unsupported version of the Socket.IO or Engine.IO protocols

I have no idea how to correct the version between flutter and flask-socketio.

my flask_socketio version is 5.0.1
and there are the flutter client packages i have tried:
https://pub.dev/packages/socket_io_client/versions/0.9.11
https://pub.dev/packages/flutter_socket_io

---

bwt, how can I check the version compatibility of flask-socketio

for example, something like this table:

JavaScript Socket.IO version	Socket.IO protocol revision	Engine.IO protocol revision	python-socketio version	python-engineio version
0.9.x	1, 2	1, 2	Not supported	Not supported
1.x and 2.x	3, 4	3	4.x	3.x
3.x	5	4	5.x	4.x

[miguelgrinberg]

I don't use the flutter client, no idea which version of the Socket.IO protocol it implements. You need to find that out. In practical terms if the protocol version 5 did not work for you, then very likely they support version 4, so you can downgrade Flask-SocketIO and its dependencies to the versions that work with version 4 and try again.

[hakanaku1234]

Thank you very much!! I will try it out :)

btw, how can I find out which version of Flask-SocketIO works with socket.io protocol version 4?

[miguelgrinberg]

how can I find out which version of Flask-SocketIO works with socket.io protocol version 4?

The docs for Flask-SocketIO have a version compatibility table.