The WebSocket readyState attribute
The WebSocket object will report the state of its connection through a read-only attribute called readyState.
There are four different values that the readyState attribute can receive to represent the state of the connection.
0 - CONNECTING – The connection has not been established yet.
1 - OPEN – The connection has been established and messages can be exchanged between the client and the server.
2 - CLOSING – The connection is going through the closing handshake.
3 - CLOSED – The connection has been closed or could not be opened.
When the WebSocket object is first created its readyState is 0, indicating that the socket is CONNECTING.