export type Ping = ["ping", number];
export type Pong = ["pong", number];
export declare class Rtt {
    private pingponger;
    constructor(pingponger: Pingponger);
    get on(): import("@e280/stz").Sub<[number]>;
    get latest(): number;
    get average(): number;
}
export declare class Pingponger {
    #private;
    options: {
        timeout: number;
        send: (p: Ping | Pong) => void;
    };
    onRtt: import("@e280/stz").Sub<[number]>;
    constructor(options: {
        timeout: number;
        send: (p: Ping | Pong) => void;
    });
    get latestRtt(): number;
    get averageRtt(): number;
    ping(): Promise<number>;
    recv([kind, id]: Ping | Pong): void;
    /** start an ongoing heartbeat */
    heartbeat(onTimeout?: (error: any) => void): () => void;
}