Future close(
[int code,
String reason]
)

Closes the WebSocket connection. Set the optional code and reason arguments to send close information to the remote peer. If they are omitted, the peer will see WebSocketStatus.NO_STATUS_RECEIVED code with no reason.

Source

/**
 * Closes the WebSocket connection. Set the optional [code] and [reason]
 * arguments to send close information to the remote peer. If they are
 * omitted, the peer will see [WebSocketStatus.NO_STATUS_RECEIVED] code
 * with no reason.
 */
Future close([int code, String reason]);