Why does adb return offline after the device strin

Question

I use "adb devices" to get following result. Only one device is connected to PC by USB, but we get 8 lines of result.

Could anyone suggest the reason?

WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline
WH96TNE00361    offline

Answer 1

I made adb working on Android 4.4.2 with GT-N8010 (Samsung tablet) after setting device in authorized mode once upgraded adb to SDK version.

~/local/opt/Android/Sdk/platform-tools/adb
Android Debug Bridge version 1.0.32

While It did not work using :

adb version   
Android Debug Bridge version 1.0.31

Shiped in Ubuntu LTS version :

apt-cache show android-tools-adb  | grep Version
Version: 4.2.2+git20130218-3ubuntu23

This link may help then

Can't connect Nexus 4 to adb: unauthorized