/**
 * In-memory, per-IP connection-*attempt* rate limiter for the TCP server. Complements
 * MAX_CONNECTIONS_PER_IP (enforced in ConnectionManager), which only bounds *concurrent*
 * connections from one IP - it does nothing to stop an attacker who stays under that cap
 * while hammering the server with rapid connect-then-drop churn, since each attempt still
 * costs a TCP handshake and an accept()/reject() cycle regardless of whether the connection
 * itself is ultimately accepted.
 *
 * Same true-sliding-window + cooldown design as LoginRateLimiter.service.ts, applied to
 * connection attempts instead of failed logins. In-memory only, reset on process restart.
 */
declare class ConnectionRateLimiter {
    private static instance;
    private readonly attempts;
    private sweepIntervalHandle;
    static getInstance(): ConnectionRateLimiter;
    /** Milliseconds remaining before this IP may open a new connection, or 0 if it's clear. */
    getCooldownRemaining(ip: string): number;
    /**
     * Records a new connection attempt, locking the IP out of further connections once the
     * threshold is crossed. Call once per accepted socket, regardless of whether the
     * connection is ultimately allowed through or rejected by the concurrent-connection cap.
     */
    recordAttempt(ip: string): void;
    startCleanupSweep(): void;
    stopCleanupSweep(): void;
    /** Test/shutdown helper - clears every tracked IP's attempt counter and any active lockouts. */
    clearAll(): void;
}
declare const _default: ConnectionRateLimiter;
export default _default;