/** Specifies the location of a message broker server. */
export interface HTTPConfig {
    /** The host that the message brokers express application is running on. */
    host: string;
    /** The port of the host that the message brokers express application is running on. */
    port: number;
    /** The base URL of the message broker. */
    path: string;
}
export interface ErrorHandler {
    (err: Error): void;
}
/** A message provided to a subscriber callback */
export interface ClientMessage {
    /** The topic name that the message was published on. */
    topicName: string;
    /** The message broker server allocated id for the message; monotonically increments per topic. */
    id: number;
    /** The data published by the publisher. */
    data: string;
}
export interface ClientCallback {
    (message: ClientMessage): void;
}
/**
 * Returns the client API to the message broker, providing publish and subscribe operations.
 * @param config Configuration specifying the server, port and base URL path of the message broker server.
 * @returns Returns a client providing publish and subscribe operations.
 */
export declare function client(config: HTTPConfig): {
    /**
     * Publishes a message to a message broker for other client to receive based on their subscriptions.
     * @param topicName The topic to publish on. This may be one or more URL segments.
     * @param data The data to publish on the topic
     * @param onError Optional error handler callback
     */
    publish: (topicName: string, data: string, onError?: ErrorHandler | undefined) => void;
    /**
     * Registers a subscription to messages on the given topic. The callback is called each time a message to published on the same topic.
     * @param topicName The topic to subscribe to. This may be one or more URL segments.
     * @param callback The function to call when data is publised on the topic; passing a message object.
     */
    subscribe: (topicName: string, callback: ClientCallback | undefined) => void;
};