Closes the connection.
Here is a list of close codes:
1000
means "normal closure" (default)1009
means a message was too big and was rejected1011
means the server encountered an error1012
means the server is restarting1013
means the server is too busy or the client is rate-limited4000
through4999
are reserved for applications (you can use it!)
To close the connection abruptly, use terminate()
.