Android Emulator lost internet connection after some time and show an error on reset "Adb connection Error:An existing connection was forcibly closed by the remote host"

Step 1 : 

Before doing anything, add your "jdk\bin" path and  "android-sdk-windows\platforms\android-4\tools" in your environment variables. 

Example : I have added following paths in my environment variables at a time separated with semicolon 

D:\Android\android-sdk-windows\tools;D:\Android\android-sdk-windows\platforms\android-4\tools;C:\Java\jdk1.7.0_05\bin;C:\Users\admin\.android;C:\openjdk-7-b146-windows-i586-20_jun_2011\java-se-7-ri\bin

Step 2 :

Open cmd and type :

adb kill-server
adb start-server

It assigns new port and then internet will be starts on your emulator.