/**
 * RPC message transport abstraction.
 *
 * A transport moves whole Cap'n Proto RPC messages (unpacked, stream-framed) between
 * two vats. WebSocket is the reference implementation: ws frames delimit messages, so
 * no additional length-prefix framing is needed.
 */
export declare function isWebSocketLike(value: unknown): value is WebSocketLike;
export interface Transport {
    close(): void;
    /** Register the (single) close/error callback. */
    onClose(cb: (err?: Error) => void): void;
    /** Register the (single) incoming-message callback. */
    onMessage(cb: (data: Uint8Array) => void): void;
    /** Send one complete RPC message. */
    send(data: Uint8Array): void;
}
/**
 * The subset of the WHATWG WebSocket surface Conn needs; satisfied by both the browser
 * WebSocket and the `ws` package's server-side sockets.
 */
export interface WebSocketLike {
    addEventListener(type: "message", listener: (event: {
        data: unknown;
    }) => void): void;
    addEventListener(type: "close", listener: () => void): void;
    addEventListener(type: "error", listener: (event: unknown) => void): void;
    addEventListener(type: "open", listener: () => void): void;
    binaryType: string;
    close(): void;
    readyState: number;
    send(data: ArrayBufferLike | ArrayBufferView): void;
}
export declare class WebSocketTransport implements Transport {
    /** Messages sent before the socket opened; flushed on open. */
    private pending?;
    private readonly ws;
    constructor(ws: WebSocketLike);
    close(): void;
    onClose(cb: (err?: Error) => void): void;
    onMessage(cb: (data: Uint8Array) => void): void;
    send(data: Uint8Array): void;
}