title: Use Twilio SIP to dial custom number
body: <p>I'm building an app and in this app I must receive an SDP packet to process it and integrate with the rest of the application. I'm thinking of using Twilio SIP to achieve this.</p>
  
  <p>I want to be able to dial a <strong>custom</strong> remote phone number and access the SDP and the way I'm thinking is by using Twilio SIP.</p>
  
  <p>In my Java app I could connect to my Twilio SIP endpoint (using any java SIP library) and I'll be able to inspect the SIP information (an thus the SDP). Using this I'm able to create a call between my app and Twilio SIP endpoint.</p>
  
  <p><strong>What I want is:</strong> how to programmatically connect to my SIP endpoint and pass a custom TwiML with the custom phone number to dial?</p>
  
  <p><strong>The problem is:</strong> When creating a new SIP endpoint it asks for a <strong>Voice Url</strong> but it is a static Url and thus a static TwiML response.</p>
  
  <p>Edit: I could set the Voice Url to an endpoint in my java web app and update the response from this endpoint before placing a call but it doesn't sound correct</p>
  
  <p><strong>Use case flow:</strong> a user visits the web app and has a webrtc connection to a Kurento media server. This user inputs a phone number in a form and sends it. The web app dials this number (via any service or api) and receives an SDP that can be used in the Kurento media server, bridging the webrtc user and the phone user in the same call</p>