Later a lot of hours study and tests, a friend in Google show me one solution for this problem!
Thanks Thiago Avancini!
Well, the solution is:
The first step is using the managed-vms. (The repo use it.)
But the goal is switch the managing from Google to User. When you do this, the next step is create an static IP for your application. On my case I using the port 3000 to serving my Websocket, feel free to change.
On my app.yaml I enable this port too like this:
network:
forwarded_ports: ["3000"]
Remember to enable this port on the proxy in "network>>default>>firewall".
If you deploy the application via gcloud, you need enable again on your application the user management and the static IP.
I'll send to GoogleCloudPlatform this repo for will be a sample for using websockets on AppEngine.