Using an Arduino as a electrical mains switch How do I make an electrical switch using Arduino, that when it receives signal (wirelessly or through a LAN port) to switch off it disconnects the switch and then again told to turn on turns the switch on? 

The main problem I am facing is that I need to give a 5V output to turn off the transmission between two wires having voltage rating of 230V.
You need to use Relays.  There all kind of relays.

Regular and Solid state ... for controlling a Regular Relay using Arduino you will need a transistor (so you will able to provide the right current to the relay to close a circle)

There are a lot of guides for Arduino and Relays (for example)