title: Asterisk call flow
body: <p>I want to use asterisk server for SIP/VOIP calls from/to android app. I searched for good Sip client and found CSip simple is good.</p>
  
  <p>Suppose there are 2 users A and B.</p>
  
  <ul>
  <li>when A wants to call to B,
  <ul>
  <li>A sends request to internal server</li>
  <li>Internal server will check if A can call B or not by populating some database value</li>
  <li>If yes, Server will ask B if it wants to accept call from A</li>
  <li>If yes, server will setup call between A and B</li>
  </ul></li>
  </ul>
  
  <p>How i should configure these things in asterisk to achieve this and also like to know that if CSipSimple will be best for android?</p>
  
  <p>If i am wrong anywhere please correct me.</p>
  
  <p>Thanks</p>