import type { UpgradeWebSocket } from '../../helper/websocket';
export interface UpgradeWebSocketOptions {
    /**
     * Sets the `.protocol` property on the client side web socket to the
     * value provided here, which should be one of the strings specified in the
     * `protocols` parameter when requesting the web socket. This is intended
     * for clients and servers to specify sub-protocols to use to communicate to
     * each other.
     */
    protocol?: string;
    /**
     * If the client does not respond to this frame with a
     * `pong` within the timeout specified, the connection is deemed
     * unhealthy and is closed. The `close` and `error` event will be emitted.
     *
     * The unit is seconds, with a default of 30.
     * Set to `0` to disable timeouts.
     */
    idleTimeout?: number;
}
export declare const upgradeWebSocket: UpgradeWebSocket<WebSocket, UpgradeWebSocketOptions>;