/// <reference types="node" />
import * as net from 'net';
import { LookupAddress } from 'dns';
import { Agent, ConnectionCb, HappyRequestArgs } from './create-connection';
import * as dns from 'dns';
export declare const core: {
    https: any;
    http: ((options: import("http").ClientRequestArgs, oncreate: (err: Error, socket: net.Socket) => void) => net.Socket) & {
        lookup?: LookupFunction | undefined;
    };
};
export declare function happyEyeballs(this: Agent, options: HappyRequestArgs, cb: ConnectionCb): Promise<void>;
export declare function zip(lookups: LookupAddress[], init?: number): Iterable<string[]>;
export declare type LookupFunction = (hostname: string, options: dns.LookupOptions, callback: (err: NodeJS.ErrnoException | undefined | null, address: string, family: number) => void) => void;