/**
 * @file association.ts
 * @description Minimal SCTP association over a datagram channel (DTLS), scoped
 * to the WebRTC data channel profile (RFC 8831).
 * @module sctp/association
 *
 * Implements the four-way INIT/INIT-ACK/COOKIE-ECHO/COOKIE-ACK setup, DATA
 * transmit/receive with TSN tracking and SACK, ordered and unordered delivery,
 * and reassembly of fragmented user messages. Congestion control is
 * intentionally simple (stop-and-go style with a generous rwnd) which is
 * adequate for control/data-channel traffic and interoperates with usrsctp
 * (the stack browsers use).
 *
 * The association rides on top of a reliable-ish datagram pipe provided by
 * DTLS; SCTP still provides framing, ordering, multiplexing and ack'ing.
 */
import { EventEmitter } from 'events';
declare const SCTP_PORT = 5000;
declare const STATE: Readonly<{
    CLOSED: "closed";
    COOKIE_WAIT: "cookie-wait";
    COOKIE_ECHOED: "cookie-echoed";
    ESTABLISHED: "established";
}>;
type StateValue = (typeof STATE)[keyof typeof STATE];
/** Options for constructing an {@link SctpAssociation}. */
export interface SctpAssociationOptions {
    /** the DTLS client initiates SCTP (RFC 8831) */
    isClient?: boolean;
}
/** A complete user message surfaced via the 'message' event. */
export interface SctpMessage {
    streamId: number;
    ppid: number;
    data: Buffer;
}
/**
 * @class SctpAssociation
 * @extends EventEmitter
 *
 * Events:
 *  - 'established'             association is up
 *  - 'message' ({streamId, ppid, data})  a complete user message arrived
 *  - 'output' (Buffer)         an SCTP packet to hand to DTLS
 *  - 'close'
 */
declare class SctpAssociation extends EventEmitter {
    #private;
    isClient: boolean;
    state: StateValue;
    /**
     * @param {Object} opts
     * @param {boolean} opts.isClient - the DTLS client initiates SCTP (RFC 8831)
     */
    constructor(opts?: SctpAssociationOptions);
    /** Start the association (client sends INIT). */
    start(): void;
    /**
     * Feed an inbound SCTP packet (decrypted from DTLS).
     * @param {Buffer} packet
     */
    receivePacket(packet: Buffer): void;
    /**
     * Send a user message on a stream.
     * @param {number} streamId
     * @param {number} ppid
     * @param {Buffer} data
     * @param {Object} [opts]
     * @param {boolean} [opts.unordered=false]
     */
    sendData(streamId: number, ppid: number, data: Buffer, opts?: {
        unordered?: boolean;
    }): void;
    /** Gracefully close the association. */
    shutdown(): void;
}
export { SctpAssociation, STATE, SCTP_PORT };