Contact Sync With the server on iphone app

Hi, This is a SIP App, and build on the code of linphone. You should have experince on Linphone,SIP,TLS. All the part are working fine, What needed to be done is to contacts are to send server and synced. There are right now 4 tabs on the app, under the contact tab it has to be divided into two parts, All contact which has all the contacts of the phone book(already present). What is required is to send all the contacts to server the server will sync the contacts and send back which are already users of the app. they have to be displayed into the second part. So basically under the contact part there will be two buttons, 1 for all contacts second for synced contacts When completed this app has to be uploaded on the iphone store as well, details will be provided.