import type { Server } from "node:http";
export type PortHolder = "humanish" | "other";
export declare class PortInUseError extends Error {
    readonly port: number;
    readonly holder: PortHolder;
    constructor(port: number, holder: PortHolder);
}
/**
 * Is the process on this port one of ours? humanish's serve and observer servers answer
 * `/_humanish/history.json` (serve) or `/observer-data.json` (observer) as JSON with a humanish
 * schema; anything else is somebody's app. Bounded to half a second and never throws: a probe
 * that cannot decide says "other", which is the answer that suggests the safer action.
 */
export declare function probePortHolder(port: number, fetchFn?: typeof fetch): Promise<PortHolder>;
/** Bind on loopback only; resolve the port that was actually bound; name a taken port. */
export declare function listenOnLoopback(server: Server, port: number, probe?: (port: number) => Promise<PortHolder>): Promise<number>;