Initialize the project as usual. Then edit settings.py to make it this way.
networks = {
"development": {
"mode": "Websocket",
"host": "localhost",
"port": 8546,
"network_id": "*"
}
}
When you run the private Geth server, use --websocket flag.
$ mamba server --websocket
Now you can enjoy Mamba with websocket.