Client web socket connection.

abstract class WebSocketClientConnection {
  /**
   * Creates a new web socket client connection based on a HTTP client
   * connection. The HTTP client connection must be freshly opened.
   */
  factory WebSocketClientConnection(HttpClientConnection conn,
                                    [List<String> protocols]) {
    return new _WebSocketClientConnection(conn, protocols);
  }

  /**
   * Sets the callback to be called when the request object for the
   * opening handshake request is ready. This callback can be used if
   * one need to add additional headers to the opening handshake
   * request.
   */
  void set onRequest(void callback(HttpClientRequest request));

  /**
   * Sets the callback to be called when a web socket connection has
   * been established.
   */
  void set onOpen(void callback());

  /**
   * Sets the callback to be called when a message have been
   * received. The type of [message] is either [:String:] or
   * [:List<int>:] depending on whether it is a text or binary
   * message. If the message is empty [message] will be [:null:].
   */
  void set onMessage(void callback(message));

  /**
   * Sets the callback to be called when the web socket connection is
   * closed. [status] indicate the reason for closing. For network
   * errors the value of [status] will be
   * WebSocketStatus.ABNORMAL_CLOSURE].
   */
  void set onClosed(void callback(int status, String reason));

  /**
   * Sets the callback to be called when the response object for the
   * opening handshake did not cause a web socket connection
   * upgrade. This will be called in case the response status code is
   * not 101 (Switching Protocols). If this callback is not set the
   * [:onError:] callback will be called if the server did not upgrade
   * the connection.
   */
  void set onNoUpgrade(void callback(HttpClientResponse response));

  /**
   * Sends a message. The [message] must be a [:String:] or a
   * [:List<int>:]. To send an empty message use either an empty
   * [:String:] or an empty [:List<int>:]. [:null:] cannot be used.
   */
  send(message);

  /**
   * Close the web socket connection. The default value for [status]
   * and [reason] are [:null:].
   */
  close([int status, String reason]);

  /**
   * WebSocketClientConnection is hashable.
   */
  int get hashCode;
}