Method verifyProtocolVersion

nodejs/src/client.ts:1816–1859

* Send the `connect` handshake (carrying the optional token) and verify the * server's protocol version. Falls back to `ping` against legacy servers * that don't implement `connect`.

()

     * that don't implement `connect`.
     */
    private async verifyProtocolVersion(): Promise<void> {
        if (!this.connection) {
            throw new Error("Client not connected");
        }
        const maxVersion = getSdkProtocolVersion();
        const raceAgainstExit = <T>(p: Promise<T>): Promise<T> =>
            this.processExitPromise ? Promise.race([p, this.processExitPromise]) : p;

        let serverVersion: number | undefined;
        try {
            const result = await raceAgainstExit(
                this.internalRpc.connect({ token: this.effectiveConnectionToken })
            );
            serverVersion = result.protocolVersion;
        } catch (err) {
            if (
                err instanceof ResponseError &&
                (err.code === ErrorCodes.MethodNotFound ||
                    err.message === "Unhandled method connect")
            ) {
                // Legacy server without `connect`; fall back to `ping`. A token, if any,
                // is silently dropped — the legacy server can't enforce one.
                serverVersion = (await raceAgainstExit(this.ping())).protocolVersion;
            } else {
                throw err;
            }
        }

        if (serverVersion === undefined) {
            throw new Error(
                `SDK protocol version mismatch: SDK supports versions ${MIN_PROTOCOL_VERSION}-${maxVersion}, but server does not report a protocol version. ` +
                    `Please update your server to ensure compatibility.`
            );
        }

        if (serverVersion < MIN_PROTOCOL_VERSION || serverVersion > maxVersion) {
            throw new Error(
                `SDK protocol version mismatch: SDK supports versions ${MIN_PROTOCOL_VERSION}-${maxVersion}, but server reports version ${serverVersion}. ` +
                    `Please update your SDK or server to ensure compatibility.`
            );
        }

        this.negotiatedProtocolVersion = serverVersion;
    }

    /**
     * Gets the ID of the most recently updated session.