import PingPongObserver from '../pingpongobserver/PingPongObserver';
/**
 * [[PingPong]] sends ping-pongs across the signaling connection via the
 * [[SignalingClient]]. It measures the round-trip time between the client ping
 * and server pong and acts as a heartbeat to keep the underlying WebSocket
 * connection alive.
 */
export default interface PingPong {
    /**
     * Adds observer to receive callbacks for pong events.
     */
    addObserver(observer: PingPongObserver): void;
    /**
     * Removes observer to stop receiving callbacks for pong events.
     */
    removeObserver(observer: PingPongObserver): void;
    /**
     * Iterates through each observer, so that their notification functions may
     * be called.
     */
    forEachObserver(observerFunc: (observer: PingPongObserver) => void): void;
    /**
     * Starts sending pings on an interval and receiving pongs.
     */
    start(): void;
    /**
     * Stops ping-pongs.
     */
    stop(): void;
}