method

ServerWebSocket.pause

pause(): void;

Stops reading from the socket, so the client sees TCP backpressure. The idle timeout is suspended until resume(). Sending still works.

Messages already read from the socket are still delivered.

message(ws, message) {
  if (!file.write(message)) {
    ws.pause();
    file.once("drain", () => ws.resume());
  }
}