title: Using GCM service for mobile chat application
body: <p>I want develop android chat app with the <strong><code>GCM</code></strong>. i had a series of questions : <br>
  1) Whether messages are sent only on devices that have Google accounts or devices that do not have a Google account to get the message?<br>
  2) Any restrictions on sending messages or the number of requests per second or minute there? <br></p>
  
  <p>** Please do not negative points and do not remove my question. I looked on the internet and did not receive a definitive answer. Here's why I raised my question.<br>
  Thanks your all my dear friens &lt;3</p>