title: more than one device/emulator react native Error in react native start
body: <p>I start my Genymotion then i do <code>npm start</code> on my <strong>react native</strong> project via VS Code . i got this message:</p>
  
  <pre><code>&gt;Press a to open android device or Emulator
  &gt;Press q to display QrCode
   .
   .
  </code></pre>
  
  <p>so i pressed a but i got this error:</p>
  
  <blockquote>
    <p>Error running adb: more than one device/emulator</p>
  </blockquote>
  
  <p>how can i solve this? i tried <code>adb devices</code> to see my devices and i saw this list:</p>
  
  <pre><code>emulator-5562 host
  emulator-5560 host
  emulator-5558 host
  192.168.X.X device
  </code></pre>
  
  <p>my OS is windows 10. i couldn't even start my react native <code>hellow-world</code> still  </p>
  
  <p><strong><em>Edit:</em></strong> i turned of my system and in next day every thing worked on . why? i checked devices again by this command:  <code>adb devices</code> this time the list includes just one device : <code>192.168.X.X device</code> so we have to have only one device as emulator but!! how can i kill all devices just one in adb? </p>