There are three ways for the Ultra Stream App to discover the encoders, via Ethernet, Wi-Fi or Bluetooth. When your smart phone and your Ultra Stream encoders are connected within the same subnet, the App will search for available devices automatically and pair your phone with the Ultra Stream encoder you choose. Even if there is no Wi-Fi network onsite, you can turn on the AP mode of the encoder via your Ultra Stream App to connect the encoder to your phone. You can check here
for how to enable the AP mode.