ANDROID:ADB error "More than one device and emulator"

Start the simulator debugging, when executing the ADB command, error.
c:\users\gaojs>adb Shell
Error:more than one device and emulator
c:\users\gaojs>adb install e:\good.apk
Error:more than one device and emulator

In this case, the first thing to check is whether there are really multiple devices or simulators.
c:\users\gaojs>ADB devices
List of devices attached
emulator-5554 Device
4DFADCB86B00CF05 Device
The discovery is really multiple devices, then you need to specify the serial number of the device for the ADB command.
c:\users\gaojs>adb-s emulator-5554 Shell
As shown above, add the-s parameter to the command!

If there is actually only one device or simulator, and check the status of offline;
That means that the ADB itself is the cause of the bug, you need to use the following methods to deal with the following:
c:\users\gaojs>adb kill-server
c:\users\gaojs>taskkill/f/im Adb.exe
The first command is to kill the ADB service, the second command is to kill the ADB process!
If the first one is useless, consider using the second command to try again!

ANDROID:ADB error "More than one device and emulator"