/// <reference types="node" />
/**
 * @packageDocumentation
 */
/**
 * Converts payload to Buffer or string regardless of the supplied type
 * @param payload The payload to convert
 * @internal
 */
export declare function normalize_payload(payload: any): Buffer | string;
/**
 * Converts payload to Buffer only, regardless of the supplied type
 * @param payload The payload to convert
 * @internal
 */
export declare function normalize_payload_to_buffer(payload: any): Buffer;
/** @internal */
export declare const DEFAULT_KEEP_ALIVE: number;
export declare function isValidTopicFilter(topicFilter: any): boolean;
export declare function isValidTopic(topic: any): boolean;