Chromecast needs some sort of connection in order to receive the media to display. Wi-Fi is the main option via a wireless router or a personal hot-spot. Google also sells an Ethernet adapter that you can plug into your wired network.
Usually Chromecast requires Internet connectivity to function, but it is possible to trick it into working on a hot-spot that lacks Internet connectivity. This work-around requires 2 Android devices for initial set-up, and the LocalCast app. The steps are described here and here.
Quote:
- Gather two devices
- One must be an Android cell phone with mobile capability. The second can be any device that is capable of local media
- open "settings" on cell phone
- open "more networks"
- select "mobile hotspot"
- turn on "mobile hotspot"
- go into "mobile hotspot" settings by selecting the 3 vertical dots in the upper-right corner
- select configure hotspot
- type in a name you would like to call your mobile hotspot network or leave the default name
- scroll down to choose a password for this network
Now we must switch the Wi-Fi network that the Chromecast is paired to.
- ensure that the second device (the one you wish to cast from) is connected to the same network that the Chromecast is paired to (the
pairing was done when you first setup your Chromecast)
- open the Chromecast app (if using iOS or Android) or open Chrome if using Linux, Windows, or MacOS
- From the app choose the name of the Chromecast or from Chrome select the Chromecast icon in the upper-right of the screen, and then
choose the name of the Chromecast
- Select "Wi-Fi"
- Select the name of the network you are on (this will drop-down a menu with other networks)
- Select the name of the mobile hotspot network you created and enter password
- This will successfully switch the network that the Chromecast looks to connect to
Now we will open LocalCast app and cast the video we desire. And
lastly we will go back to the cell phone and turn off "mobile data"
and leave on "mobile hotspot"