Closes the connection.
Here is a list of close codes:
- 1000means "normal closure" (default)
- 1009means a message was too big and was rejected
- 1011means the server encountered an error
- 1012means the server is restarting
- 1013means the server is too busy or the client is rate-limited
- 4000through- 4999are reserved for applications (you can use it!)
To close the connection abruptly, use terminate().