Function _tryUpgrade

packages/socket.io-cluster-engine/lib/engine.ts:486–524

(
    transport: Transport,
    onSuccess: () => void,
    onError: () => void,
  )

  }

  private _tryUpgrade(
    transport: Transport,
    onSuccess: () => void,
    onError: () => void,
  ) {
    debug(class="st">"starting upgrade process");

    const upgradeTimeoutTimer = setTimeout(() => {
      debug(class="st">"client did not complete upgrade - closing transport");
      transport.close();
      transport.removeAllListeners();
      onError();
    }, this.opts.upgradeTimeout);

    transport.on(class="st">"packet", (packet) => {
      if (packet.type === class="st">"ping" && packet.data === class="st">"probe") {
        debug(class="st">"got probe ping packet, sending pong");
        transport.send([{ type: class="st">"pong", data: class="st">"probe" }]);
      } else if (packet.type === class="st">"upgrade") {
        clearTimeout(upgradeTimeoutTimer);
        transport.removeAllListeners();
        onSuccess();
      } else {
        transport.removeAllListeners();
        transport.close();
        onError();
      }
    });

    transport.on(class="st">"error", () => {
      transport.removeAllListeners();
      onError();
    });

    transport.on(class="st">"close", () => {
      transport.removeAllListeners();
      onError();
    });
  }

  private _onPacket(sid: SessionId, senderId: NodeId, packet: Packet) {
    this.publishMessage({