In this Instructables, I will show you how to use raspberry pi 3 as Chromecast alternative. It is also worth mentioning that this is not a direct clone to Chromecast and that there are limitations. This method does not support the cast button but will stream Youtube videos as well as local audio and video files directly from your smartphone using an Android application. And I believe this application is only for android devices.
So, actually what is Chromecast?
Chromecast is a streaming media adapter from Google that allows users to play online content such as videos and music on a digital television.
The adapter is a dongle that plugs into the TV's HDMI port; a cable connects to a USB port to power the device. A mobile app makes it possible to essentially use a smartphone, tablet, laptop or desktop computer as a TV remote. Once the streaming begins, it's not necessary to keep the app open, and the device can be used for other purposes. Chromecast can stream content from an increasing number of sources including Netflix, Hulu Plus, YouTube, Google Play music and movies and the Chrome browser.
Once everything is compiled discover your Pi's IP address so that you can connect to it over the network. To do this, click on the black terminal icon on the top bar of the Raspbian desktop to open the Terminal.
Type "ifconfig" and then find the wireless IP address ("inet addr") under "wlan0" that will look something like 192.168.43.252 and make a note of it. Note it is not "192.168.43.252", there should be a different address under "wlan0".
Make sure your raspberry pi and phone are connected to same WiFi network.
$ ifconfig
After everything is downloaded Open the software and click on the three dots on the top right corner, then you will be asked for an Hostname or IP address. At this point you now insert the IP address you got earlier along with the Username and password on your raspberry pi.
The default username will be "pi". Leave port to 22 as itself
Now you can open your YouTube app and select a video to cast. Then but clicking the share icon look for the “raspicast”.
You can also cast Pictures, Music and Videos which or on your Device directly to target destination.