title: Is it possible log in with existing xmpp user using gcm css?
body: <p>I am developing an android chat application using gcm css. My question is that I have already registered user on my xmpp server and I want to login those user using gcm xmpp. I read the google developer tutorials for cloud messaging <a href="https://developers.google.com/cloud-messaging/gcm" rel="nofollow">https://developers.google.com/cloud-messaging/gcm</a>, but there are not much information as per my requirement.</p>
  
  <p>I have some other query as well:-</p>
  
  <p>1)  Is gcm server manage users if manage how it manage? Now, We can send message like push notification on particular registration Id. (Using Downstream), But if user uninstall and install the app again then registration id will be changed. So, In this case how can we manage? Will I need the separate server?</p>
  
  <p>If any one have idea. Please reply.</p>
  
  <p>Thanks in advance...</p>