/** WHATWG `WebSocket` subset used by the transport. Both `ws` and the native
 * browser `WebSocket` satisfy this. */
export interface SocketLike {
    readyState: number;
    send(data: string): void;
    close(): void;
    addEventListener(type: string, listener: (event: any) => void, options?: {
        once?: boolean;
    }): void;
    removeEventListener(type: string, listener: (event: any) => void): void;
}
/** `WebSocket.OPEN` — always `1` per the WHATWG spec. */
export declare const OPEN = 1;
/** Factory contract for `createWebSocket`, shared by both platform bindings.
 * `protocols` selects a WebSocket subprotocol — the client always requests
 * `graphql-transport-ws`, the single protocol carrying every BrowserQL op. */
export type CreateWebSocket = (url: string, headers?: Record<string, string>, protocols?: string | string[]) => SocketLike;
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