App where users can send images to each other
<p>I am thinking about making an android app in which you can send pictures to your contacts (grabbed from you address book). Sort of what the app WhatsApp does.
I was wondering, how is something like that achieved? I mean what would be the general design for it?</p>

<p>Any help/tip is appreciated</p>

<p>Thank you</p>

<p>EDIT: As a clarification, I am not looking for general answer of how to do this app from A to Z. I want to know specifically of the design architecture in terms how to link to users together using phone number. Would I have a server that stores all phone numbers of my users? Or is there som android functionality that can piggy back on phone number </p>
