Method onerror

packages/engine.io-client/lib/socket.ts:1066–1076

(err)

    // Handle any error that happens while probing
    const onerror = (err) => {
      const error = new Error("probe error: " + err);
      // @ts-ignore
      error.transport = transport.name;

      freezeTransport();

      debug('probe transport "%s" failed because of error: %s', name, err);

      this.emitReserved("upgradeError", error);
    };

    function onTransportClose() {
      onerror("transport closed");