For such scenario there nice and simple available in Google play store which automatically start your computer when you reach your home. App uses wake on LAN service which is available on almost every computer and send the magic packet using your home WiFi the name of App is same what it do, app name is I’m Home.
How I’m Home app works
When you first run the app in your device it will turn on configuration window. In first field enter Brodcast IP of your computer and then enter MAC address of your PC and then enter port number 7 or 9 (you have to test it by own that which port number your PC using for Wake on LAN service). Then enter name of wifi in SSID field. Once you have filled all fields properly then click SEND TEST button. If your configuration is working app will save your configuration. Next time when your Android phone connect to your wifi network it will automatically boot your computer.