Hi there,
I think the issue could be related to socket.io library. I have tried using a python based server and ofxLibwebSocket sample works fine. If I am not wrong, socket.io adds some abstractions such as channels/topics on top of the websocket api that this addon does not support.
Try with this simple python (2.7) module:
https://github.com/dpallot/simple-websocket-server
And as a test, change the port number for example_client_hello_world sample that comes with ofxLibWebsockets to 8000 and give it a try.
Mine is tested on Mac.
hope it helps
dece